Patent Publication Number: US-2022227061-A1

Title: Additive manufacturing systems and methods of pretreating and additively printing on workpieces

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 16/434,384, filed Jun. 7, 2019, the contents of which are incorporated herein by reference in its entirety as if set forth verbatim. 
    
    
     FIELD 
     The present disclosure generally pertains to additive manufacturing systems and methods of additively printing on workpieces, and more particularly to systems and methods that include a vision system configured to locate workpieces and an additive manufacturing machine configured to pretreat workpieces and additively print on the pretreated workpieces. 
     BACKGROUND 
     An additive manufacturing machine or system may be utilized to produce components according to a three-dimensional computer model. A model of the component may be constructed using a computer aided design (CAD) program, and an additive manufacturing machine or system may additively print the component according to the model. With previous additive manufacturing machines or systems, typically, components are additively printed on a build plate and/or within a build chamber. After the additive printing process is completed, the components are removed from the build plate and/or the build chamber for further processing. The build plate and/or the build chamber are not part of the component being additively printed, but rather, the build plate and the build chamber respectively provide a surface and/or a medium to support components during the additive printing process. As a result, the specific location of the final additively printed components on the build plate and/or within the build chamber may not be of particular importance provided that the components are successfully printed as intended by the CAD model. 
     However, according to the present disclosure, it would be desirable to utilize an additive manufacturing machine or system to additively print onto pre-exiting workpieces, including additively printing onto a plurality of pre-existing workpieces as part of a single build. When additively printing onto such workpieces, it would be desirable for additive manufacturing machines, systems, and methods to additively print onto pre-existing workpieces with sufficient precision and accuracy so as to provide near net shape components. Accordingly, there exists a need for improved additive manufacturing machines and systems, and methods of additively printing on workpieces. 
     It is contemplated in the present disclosure that when additively printing on a workpiece, it is desirable for the material additively printed thereon to sufficiently bond with the workpiece. In a powder-based additive manufacturing system, sequential layers of powder are bonded (e.g., melted or fused) to one another using an energy source that has a focal point generally corresponding to the elevation of the layer of powder being melted or fused to material immediately below such layer. However, when additively printing on a pre-existing workpiece, variation in the elevation across a surface of a workpiece may cause variations or interruptions in the powder spread across the surface of the workpiece as well as the bond between the surface of the workpiece and the sequential layer of powder being melted or fused thereto. Additionally, the surface of a pre-existing workpiece may have oxidation or other surface features that may affect the bonding of powder thereto. Accordingly, there further exists a need for improved additive manufacturing machines and systems, and methods of pretreating and additively printing on workpieces. 
     The workpieces contemplated by the present disclosure include originally fabricated workpieces, as well as workpieces intended to be repaired, rebuilt, upgraded, and so forth, such as machine or device components that may experience damage, wear, and/or degradation throughout their service life. It would be desirable to additively print on workpieces such as machine or device components so as to repair, rebuild, or upgrade such components. It would also be desirable to additively print on workpieces so as to produce new components such as components that may exhibit an enhanced performance or service life. 
     One example of a machine or device component includes an air foil, such as a compressor blade or a turbine blade used in a turbomachine. These air foils frequently experience damage, wear, and/or degradation throughout their service life. For example, serviced air foils, such as compressor blades of a gas turbine engine show erosion, defects, and/or cracks after long term use. Specifically, for example, such blades are subject to significant high stresses and temperatures which inevitably cause blades to wear over time, particularly near the tip of the blade. For example, blade tips are susceptible to wear or damage from friction or rubbing between the blade tips and turbomachine shrouds, from chemical degradation or oxidation from hot gasses, from fatigue caused by cyclic loading and unloading, from diffusion creep of crystalline lattices, and so forth. 
     Notably, worn or damaged blades may result in machine failure or performance degradation if not corrected. Specifically, such blades may cause a turbomachine to exhibit reduced operating efficiency as gaps between blade tips and turbomachine shrouds may allow gasses to leak through the turbomachine stages without being converted to mechanical energy. When efficiency drops below specified levels, the turbomachine is typically removed from service for overhaul and repair. Moreover, weakened blades may result in complete fractures and catastrophic failure of the engine. 
     As a result, compressor blades for a turbomachine are typically the target of frequent inspections, repairs, or replacements. It is typically expensive to replace such blades altogether, however, some can be repaired for extended lifetime at relatively low cost (as compared to replacement with new blades). Nevertheless, traditional repair processes tend to be labor intensive and time consuming. 
     For example, a traditional repair process uses a welding/cladding technique whereby repair material may be supplied to a repair surface in either powder or wire form, and the repair material may be melted and bonded to the repair surface using a focused power source such as a laser, e-beam, plasma arc, or the like. However, blades repaired with such a welding/cladding technique also undergo tedious post-processing to achieve the target geometry and surface finish. Specifically, due to the bulky feature size of the welding/cladding repair material bonded to the repair surface, the repaired blades require heavy machining to remove extra material followed by polishing to achieve a target surface finish. Notably, such machining and polishing processes are performed on a single blade at a time, are labor intensive and tedious, and result in large overall labor costs for a single repair. 
     Alternatively, other direct-energy-deposition (DED) methods may be used for blade repair, e.g., such as cold spray, which directs high-speed metal powders to bombard the target or base component such that the powders deform and deposit on the base component. However, none of these DED methods are suitable for batch processing or for repairing a large number of components in a time-efficient manner, thus providing little or no business value. 
     Accordingly, it would be desirable to provide improved system and method for repairing or rebuilding serviced components. More particularly, additive manufacturing machines and systems for quickly and effectively rebuilding or repairing worn compressor blades would be particularly desirable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended Figures, in which: 
         FIGS. 1A and 1B  schematically depict exemplary additive manufacturing systems; 
         FIG. 2A  schematically depicts an exemplary workpiece-assembly that includes a plurality of workpieces secured to a build plate: 
         FIG. 2B  schematically depicts the exemplary workpiece-assembly of  FIG. 2A , with a plurality of components by additively printing extension segments the plurality of workpieces secured to the build plate; 
         FIGS. 3A and 3B  respectively depict a plurality of workpieces misaligned with a build plane, and a recoater consequently failing to successfully apply a uniform layer of powder across the build plane: 
         FIGS. 3C and 3D  respectively depict a plurality of workpieces aligned with a build plane, and a recoater successfully applying a uniform layer of powder across the build plane: 
         FIG. 4  shows a flowchart depicting an exemplary method of additively printing an extension segment on a workpiece-interface of a workpiece; 
         FIGS. 5A and 5B  schematically depicts an exemplary workpiece before and after subjecting the workpiece to a subtractive modification, respectively: 
         FIG. 5C  schematically depicts an exemplary component formed by additively printing an extension segment on the workpiece depicted in  FIG. 5B : 
         FIG. 6A  schematically depicts an exemplary digital representation of a field of view that includes a workpiece, captured using a vision system: 
         FIG. 6B  schematically depicts an exemplary digital representation of one or more fields of view that includes a plurality of workpieces, captured using the vision system: 
         FIG. 7A  shows a flowchart depicting an exemplary method of determining a workpiece, a workpiece-interface, and/or a workpiece-interface perimeter; 
         FIG. 7B  shows a flowchart depicting an exemplary method of generating a print command; 
         FIG. 8A  schematically depicts an exemplary extension segment-CAD model that include a model of a plurality of extension segments; 
         FIG. 8B  schematically depicts an exemplary library-CAD model that includes a nominal model of a plurality of nominal workpieces: 
         FIGS. 9A and 9B  show a flowchart depicting an exemplary method of generating an extension segment-CAD model; 
         FIGS. 10A-10D  schematically depict exemplary transforming operations which may be performed so as to conform a nominal model-interface to a digital representation of a workpiece-interface, such as in the exemplary method depicted in  FIGS. 9A and 9B : 
         FIG. 11A  schematically depicts an exemplary nominal model, such as from a library-CAD model; 
         FIG. 11B  schematically depicts an exemplary model of an extension segment, such as in an extension segment-CAD model; 
         FIGS. 12A-12D  show flowcharts depicting exemplary methods of extending a model-interface which may be performed so as to define a model of an extension segment extending in the z-direction from a model-interface to a nominal extended-plane, such as in the exemplary method depicted in  FIGS. 9A and 9B ; 
         FIG. 13  schematically depicts an exemplary print command for additively printing a slice of a plurality of extension segments; 
         FIG. 14  shows a flowchart depicting an exemplary method of generating a pretreatment command; 
         FIGS. 15A-15R  schematically depict exemplary aberrant workpiece-interfaces, exemplary pretreatment-CAD models, and exemplary pretreated workpiece-interfaces respectively corresponding to one another: 
         FIG. 16A  schematically depicts a digital representation of a plurality of workpieces having an aberrant workpiece-interface, with the workpieces situated in a workpiece alignment system and a scratch-coating of powder applied thereto; 
         FIG. 16B ; schematically depicts a digital representation of a plurality of workpieces situated in a workpiece alignment system after having a pretreatment applied to the aberrant workpiece-interfaces thereof: 
         FIG. 17  schematically depicts an enlarged view of an exemplary pretreated workpiece-interface; 
         FIGS. 18A and 18B  show a flowchart depicting an exemplary method of generating a pretreatment-CAD model; 
         FIG. 19  schematically depicts an exemplary pretreatment command for pretreating a plurality of aberrant workpiece-interfaces; 
         FIG. 20  schematically depicts an exemplary calibration-CAD model; 
         FIG. 21  schematically depicts an exemplary calibration surface that includes a plurality of printed calibration marks that were printed using an additive manufacturing machine; 
         FIG. 22  schematically depicts an exemplary digital representation of a field of view that includes a plurality of calibration marks having been obtained using a vision system; 
         FIG. 23  schematically depicts an exemplary comparison table illustrating an exemplary comparison of respective ones of a plurality of digitally represented calibration marks to corresponding respective ones of a plurality of model calibration marks; 
         FIG. 24A  schematically depicts an exemplary digital representation of a workpiece-interface obtained from a vision system before calibration and after calibration, such as for a calibration adjustment applied to the vision system; 
         FIG. 24B  schematically depicts an exemplary location of an extension segment additively printed using an additive manufacturing machine before calibration and after calibration, such as for a calibration adjustment applied to the additive manufacturing machine; 
         FIG. 24C  schematically depicts an exemplary location of a model of an extension segment in an extension-segment CAD model before calibration and after calibration, such as for a calibration adjustment applied to the extension-segment CAD model; 
         FIG. 25  shows a flowchart depicting an exemplary method of calibrating an additive manufacturing system; and 
         FIG. 26  shows a block diagram depicting an exemplary control system of an additive manufacturing system. 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present disclosure. 
     DETAILED DESCRIPTION 
     Reference now will be made in detail to exemplary embodiments of the presently disclosed subject matter, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation and should not be interpreted as limiting the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     It is understood that terms such as “top”. “bottom”, “outward”, “inward”, and the like are words of convenience and are not to be construed as limiting terms. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. 
     Here and throughout the specification and claims, range limitations are combined and interchanged, and such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. 
     Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. 
     As described in detail below, exemplary embodiments of the present subject matter involve the use of additive manufacturing machines or methods. As used herein, the terms “additively manufactured” or “additive manufacturing techniques or processes” refer generally to manufacturing processes wherein successive layers of material(s) are provided on each other to “build-up,” layer-by-layer, a three-dimensional component. The successive layers generally fuse together to form a monolithic component which may have a variety of integral sub-components. 
     As used herein, the term “near net shape” refers to an additively printed feature that has an as-printed shape that is very close to the final “net” shape. A near net shape component may undergo surface finishing such as polishing, buffing, and the like, but does not require heaving machining so as to achieve a final “net” shape. By way of example, a near net shape may differ from a final net shape by about 1,500 microns or less, such as about 1,000 μm or less, such as about 500 μm or less, such as about 250 μm or less, such as about 150 μm or less, such as about 100 μm or less, such as about 50 μm or less, or such as about 25 μm or less. 
     Although additive manufacturing technology is described herein as enabling fabrication of complex objects by building objects point-by-point, layer-by-layer, typically in a vertical direction, other methods of fabrication are possible and within the scope of the present subject matter. For example, although the discussion herein refers to the addition of material to form successive layers, one skilled in the art will appreciate that the methods and structures disclosed herein may be practiced with any additive manufacturing technique or manufacturing technology. For example, embodiments of the present invention may use layer-additive processes, layer-subtractive processes, or hybrid processes. 
     Suitable additive manufacturing techniques in accordance with the present disclosure include, for example, Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjets and laserjets, Sterolithography (SLA), Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS). Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), Laser Net Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), Digital Light Processing (DLP). Direct Selective Laser Melting (DSLM). Selective Laser Melting (SLM), Direct Metal Laser Melting (DMLM), and other known processes. 
     In addition to using a direct metal laser sintering (DMLS) or direct metal laser melting (DMLM) process where an energy source is used to selectively sinter or melt portions of a layer of powder, it should be appreciated that according to alternative embodiments, the additive manufacturing process may be a “binder jetting” process. In this regard, binder jetting involves successively depositing layers of additive powder in a similar manner as described above. However, instead of using an energy source to generate an energy beam to selectively melt or fuse the additive powders, binder jetting involves selectively depositing a liquid binding agent onto each layer of powder. The liquid binding agent may be, for example, a photo-curable polymer or another liquid bonding agent. Other suitable additive manufacturing methods and variants are intended to be within the scope of the present subject matter. 
     The additive manufacturing processes described herein may be used for forming components using any suitable material. For example, the material may be plastic, metal, concrete, ceramic, polymer, epoxy, photopolymer resin, or any other suitable material that may be in solid, liquid, powder, sheet material, wire, or any other suitable form. More specifically, according to exemplary embodiments of the present subject matter, the additively manufactured components described herein may be formed in part, in whole, or in some combination of materials including but not limited to pure metals, nickel alloys, chrome alloys, titanium, titanium alloys, magnesium, magnesium alloys, aluminum, aluminum alloys, iron, iron alloys, stainless steel, and nickel or cobalt based superalloys (e.g., those available under the name Inconel® available from Special Metals Corporation). These materials are examples of materials suitable for use in the additive manufacturing processes described herein and may be generally referred to as “additive materials.” 
     In addition, one skilled in the art will appreciate that a variety of materials and methods for bonding those materials may be used and are contemplated as within the scope of the present disclosure. As used herein, references to “fusing” may refer to any suitable process for creating a bonded layer of any of the above materials. For example, if an object is made from polymer, fusing may refer to creating a thermoset bond between polymer materials. If the object is epoxy, the bond may be formed by a crosslinking process. If the material is ceramic, the bond may be formed by a sintering process. If the material is powdered metal, the bond may be formed by a melting or sintering process. One skilled in the art will appreciate that other methods of fusing materials to make a component by additive manufacturing are possible, and the presently disclosed subject matter may be practiced with those methods. 
     In addition, the additive manufacturing process disclosed herein allows a single component to be formed from multiple materials. Thus, the components described herein may be formed from any suitable mixtures of the above materials. For example, a component may include multiple layers, segments, or parts that are formed using different materials, processes, and/or on different additive manufacturing machines. In this manner, components may be constructed which have different materials and material properties for meeting the demands of any particular application. In addition, although the components described herein are constructed by additive manufacturing processes, it should be appreciated that in alternate embodiments, all or a portion of these components may be formed via casting, machining, and/or any other suitable manufacturing process. Indeed, any suitable combination of materials and manufacturing methods may be used to form these components. 
     An exemplary additive manufacturing process will now be described. Additive manufacturing processes fabricate components using three-dimensional (3D) information, for example a three-dimensional computer model, of the component. Accordingly, a three-dimensional design model of the component may be defined prior to manufacturing. In this regard, a model or prototype of the component may be scanned to determine the three-dimensional information of the component. As another example, a model of the component may be constructed using a suitable computer aided design (CAD) program to define the three-dimensional design model of the component. 
     The design model may include 3D numeric coordinates of the configuration of the component including both external and internal surfaces of the component. For example, the design model may define the body, the surface, and/or internal passageways such as openings, support structures, etc. In one exemplary embodiment, the three-dimensional design model is converted into a plurality of slices or segments, e.g., along a central (e.g., vertical) axis of the component or any other suitable axis. Each slice may define a thin cross section of the component for a predetermined height of the slice. The plurality of successive cross-sectional slices together form the 3D component. The component is then “built-up” slice-by-slice, or layer-by-layer, until finished. 
     In this manner, the components described herein may be fabricated using the additive process, or more specifically each layer is successively formed. e.g., by fusing or polymerizing a plastic using laser energy or heat or by sintering or melting metal powder. For example, a particular type of additive manufacturing process may use an energy beam, for example, an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt a powder material. Any suitable laser and laser parameters may be used, including considerations with respect to power, laser beam spot size, and scanning velocity. The build material may be formed by any suitable powder or material selected for enhanced strength, durability, and useful life, particularly at high temperatures. 
     Each successive layer may be, for example, between about 10 μm and 200 μm, although the thickness may be selected based on any number of parameters and may be any suitable size according to alternative embodiments. Therefore, utilizing the additive formation methods described above, the components described herein may have cross sections as thin as one thickness of an associated powder laver, e.g., 10 μm, utilized during the additive formation process. 
     In addition, utilizing an additive process, the surface finish and features of the components may vary as need depending on the application. For example, the surface finish may be adjusted (e.g., made smoother or rougher) by selecting appropriate laser scan parameters (e.g., laser power, scan speed, laser focal spot size, etc.) during the additive process, especially in the periphery of a cross-sectional layer which corresponds to the part surface. For example, a rougher finish may be achieved by increasing laser scan speed or decreasing the size of the melt pool formed, and a smoother finish may be achieved by decreasing laser scan speed or increasing the size of the melt pool formed. The scanning pattern and/or laser power can also be changed to change the surface finish in a selected area. 
     After fabrication of the component is complete, various post-processing procedures may be applied to the component. For example, post processing procedures may include removal of excess powder by, for example, blowing or vacuuming. Other post processing procedures may include a stress relief process. Additionally, thermal, mechanical, and/or chemical post processing procedures can be used to finish the part to achieve a desired strength, surface finish, and other component properties or features. 
     Notably, in exemplary embodiments, several aspects and features of the present subject matter were previously not possible due to manufacturing restraints. However, the present inventors have advantageously utilized current advances in additive manufacturing techniques to improve various components and the method of additively manufacturing such components. While the present disclosure is not limited to the use of additive manufacturing to form these components generally, additive manufacturing does provide a variety of manufacturing advantages, including ease of manufacturing, reduced cost, greater accuracy, etc. 
     Also, the additive manufacturing methods described above enable much more complex and intricate shapes and contours of the components described herein to be formed with a very high level of precision. For example, such components may include thin additively manufactured layers, cross sectional features, and component contours. In addition, the additive manufacturing process enables the manufacture of a single component having different materials such that different portions of the component may exhibit different performance characteristics. The successive, additive nature of the manufacturing process enables the construction of these novel features. As a result, components formed using the methods described herein may exhibit improved performance and reliability. 
     The present disclosure generally provides additive manufacturing machines, systems, and methods configured to pretreat and additively print on pre-existing workpieces. The pre-existing workpieces may include new workpieces as well as workpieces being repaired, rebuilt, or upgraded. The presently disclosed additive manufacturing systems and methods utilize a vision system to capture digital representations of one or more workpieces situated in a field of view, which may be in the form of digital images or the like. The shape and location of each workpiece may be determined using the vision system and pretreatment commands and/or print commands may be generated based at least in part on the digital representation of the one or more workpieces. The pretreatment commands may be configured to cause an additive manufacturing machine to utilize an energy source of the additive manufacturing machine to pretreat one or more workpieces, and the print commands may be configured to cause an additive manufacturing machine to additively print an extension segment directly on each of the one or more workpieces. 
     The workpieces may include a workpiece-interface, which refers to a surface that may be pretreated using the energy source from the additive manufacturing machine and upon which an additive manufacturing machine may additively print an extension segment. For some workpieces, the workpiece-interface may include a surface that has undergone pre-processing prior to such pretreatment and in preparation for additively printing. For example, a surface may be machined, ground, brushed, etched, polished, or otherwise substantively modified so as to provide a workpiece-interface. Such subtractive modification may remove at least a portion of a surface that has been worn or damaged, and/or may improve bonding between the workpiece and the additively printed material. In the case of previously used components, such as compressor blades or turbine blades, the surface may be damaged or worn to some degree, including artifacts such as microcracks, pits, abrasions, defects, foreign material, depositions, imperfections, and the like. The subtractive modification process may remove such damage or wear to provide a workpiece with a workpiece-interface that is ready for additive printing. The workpiece-interface resulting from such subtractive modification may be pretreated according to the present disclosure, and an extension segment may be additively printed on the pretreated workpiece-interface. However, in some embodiments, the subtractive modification and/or the pretreatment may be omitted, for example, when a workpiece includes a workpiece-interface suitable for additively printing thereon. Of course, a subtractive modification and/or a pretreatment may be performed even when a workpiece includes a suitable workpiece-interface, for example, to provide an improved workpiece-interface. 
     One exemplary type of workpiece includes airfoils for a turbomachine, such as compressor blades and/or turbine blades. A typical turbomachine includes one or more compressor sections, each of which may include multiple compressor stages, and one or more turbine sections, each of which may include multiple turbine stages. The compressor sections and turbine sections are typically oriented along an axis of rotation and respectively include a series of airfoils disposed circumferentially around the respective stage and circumferentially surrounded by a shroud. 
     Typically, the nature and extent of damage or wear to a set of blades removed from a turbomachine for repair or rebuild varies from blade to blade. As a result, the amount of material that may need to be removed during a subtractive modification process so as to prepare a workpiece-interface may vary from one blade to the next. Additionally, some of the blades may be deformed from their original net shape through exposure to high stresses and temperatures and/or through damage from rubbing on shrouds and so forth. As a result, each individual blade may differ from its original net shape in varying degrees from one blade to the next. 
     Additionally, the size and shape of the airfoils may differ from one stage to the next, and the tips of the airfoils provides a relatively small workpiece-interface. As an example, exemplary high-pressure compressor blades may be about 1 to 2 inches tall and may have a blade tip with a cross-sectional width of about 0.5 mm to about 5 mm, which provides for a particularly small workpiece-interface, which provides for a particularly small workpiece-interface. Other exemplary high-pressure compressor blades, as well as low-pressure compressor blades and blades from a turbine section (e.g., high-pressure turbine blades and low-pressure turbine blades) may be somewhat larger, such as up to about 10 inches tall, but nevertheless provide for a small workpiece-interface. 
     This variability from one workpiece to the next, including variability as to differences from original net shape, differing amounts of subtractive modification, and/or differences in size and shape, presents several key challenges in additively printing on the workpiece-interface of such workpieces, which are addressed by the present disclosure. In particular, the present disclosure provides for additively printing extension segments on the workpiece-interface of respective workpieces with sufficient precision and accuracy so as to provide near net shape components even though the respective workpieces may differ from one another because of one or more of such sources of variability. 
     In some embodiments, the present disclosure provides systems and methods of securing workpieces to a build plate and/or within a build chamber so that an additive manufacturing machine or system may additively print onto the workpiece-interfaces of the respective workpieces as part of a common build even when the workpieces have different sizes or shapes. For example, the present disclosure provides build plates that include one or more biasing members configured to align the workpiece-interfaces with one another, and one or more clamping mechanisms which operate to secure the workpieces to the build plate. The workpieces may be secured to the build plate at locations which may be determined by registration points mapped to a coordinate system that may be utilized by the additive manufacturing system to locate the workpieces and/or their workpiece-interfaces. 
     The present disclosure provides systems and methods of pretreating workpiece-interfaces, such as those having one or more aberrant features. The pretreatment may remediate aberrant features and/or enhance one or more features of the workpiece-interface. For example, the pretreatments may level one or more regions of the workpiece-interface and/or may provide desirable metallurgical properties across one or more regions of the workpiece-interface. The pretreatment may also improve bonding between the workpiece and an extension segment additively printed on the workpiece following pretreatment. Additionally, the pretreatment may improve the precision and/or accuracy with which an extension segment may be additively printed on a workpiece. Exemplary pretreatments may include additive-leveling, melt-leveling, and/or heat-conditioning. In some embodiments, a workpiece-interface may be leveled using a pretreatment that includes additive-leveling and/or melt-leveling. Additionally, or in the alternative, a pretreatment may remove oxidation, contaminants, debris, and/or subtractive modification artifacts (e.g., grooves, scratches, burrs, etc.) from the workpiece-interface  120 . 
     In some embodiments, the present disclosure provides systems and methods of determining or generating a CAD model that includes a model of one or more extension segments, such as an extension segment-CAD model, that conform to the location and shape of one or more corresponding workpieces upon which the extension segments are to be additively printed. Such an extension segment-CAD model may be utilized to generate print commands for an additive manufacturing machine, allowing the additive manufacturing machine to additively print extension segments onto workpiece-interfaces with sufficient precision or accuracy to provide near net shape components. 
     The present disclosure provides for determining and/or generating an extension segment CAD model, for example, from a library-CAD model that includes a nominal model of one or more nominal workpieces, components, or extension segments. The library-CAD model may be selected from a library of CAD models based at least in part on a digital representation of a field of view of one or more workpiece-interfaces obtained from the vision system. A nominal model-interface traversing a nominal model may be determined in a library-CAD model, and a model of an extension segment may be selected and/or generated based at least in part on a comparison of the nominal model-interface to a digital representation of a workpiece-interface. A model of one or more extension segments may be output to an extension segment-CAD model and print commands for the additive manufacturing machine may be generated using the extension segment-CAD model. 
     The present disclosure additionally provides for determining and/or generating a pretreatment-CAD model. By way of example, a pretreatment-CAD model may be determined or generated from an extension segment-CAD model and/or from a library-CAD model that includes a nominal model of one or more nominal workpieces, components, or extension segments. A model of a pretreatment region may be selected and/or generated based at least in part on a comparison of a nominal model-interface to a digital representation of a workpiece-interface. A model of one or more pretreatment regions may be output to a pretreatment-CAD model and pretreatment commands for pretreating workpiece-interfaces may be generated using the pretreatment-CAD model. 
     In some embodiments, generating a model of an extension segment may include extracting the nominal model-interface from the nominal model, transforming the nominal model-interface based at least in part on the comparison to the digital representation of the workpiece-interface, and/or extending the transformed model-interface so as to provide the model of the extension segment. Additionally, or in the alternative, a model of an extension segment may be generated from a three-dimensional portion of a nominal model, which may include transforming such three-dimensional portion so as to provide a model of an extension segment conforming to the digital representation of the workpiece-interface. Similarly, generating a model of a pretreatment region may include extracting a nominal model-interface from the nominal model, transforming the nominal model-interface based at least in part on a comparison to the digital representation of the workpiece-interface, and/or extending the transformed model-interface so as to provide the model of the pretreatment region. Additionally, or in the alternative, a model of a pretreatment region may be generated from a three-dimensional portion of a nominal model, which may include transforming such three-dimensional portion so as to provide a model of a pretreatment region conforming to the digital representation of the workpiece-interface. 
     The present disclosure also provides for systems and methods of performing calibration adjustments so as to prevent or mitigate discrepancies, biases, misalignments, calibration errors, or the like which may otherwise arise from time to time as between one or more aspects of the additive manufacturing system. Such calibration adjustments may be configured to address potential discrepancies, biases, misalignments, calibration errors, or the like between a vision system and an additive manufacturing machine, between a vision system and one or more CAD models generated, or between one or more CAD models and an additive manufacturing machine, as well as combinations of these. 
     When additively printing an extension segment on a workpiece-interface, misalignment between the workpiece and the extension segment may result in a failed build or a defective component. Previous additive manufacturing system may exhibit systematic bias in the mapping between the scan path coordinates and the coordinates of a CAD model. Such systematic bias may cause additively printed components to be shifted globally, which may have been of little consequence for previous additive manufacturing systems. However, the present disclosure provides for near net shape components, such that the extension segment conforms to the location and shape of the workpiece-interface of the workpiece. To provide such near net shape components, not only is the precision of the additive manufacturing tool of importance, but it is also of importance that the location and shape of the workpieces and corresponding extension segments be accurately and precisely aligned with one another. 
     In some embodiments, the additive material used for the extension segments may differ from the material of the workpieces. Differences in material may provide for different properties or performance characteristics of the extension segments relative to the workpieces, including enhanced wear resistance, improved hardness, strength, and/or ductility. New or unused components may be additively manufactured or upgraded in accordance with the present disclosure so as to provide an extension segment with a material that differs from that of the workpiece. For example, airfoils such as compressor blades or turbine blades may be upgraded with blade tips formed of a superior performing material. Likewise, damaged or worn components may be repaired or rebuild using a material that differs from that of the workpiece, for example, using a superior performing material. Further, a material used in connection with a pretreatment may differ from a material used for an extension segment and/or a material included in the workpiece. 
     Exemplary embodiments of the present disclosure will now be described in further detail. Exemplary embodiments of an additive manufacturing system  100  are shown in  FIGS. 1A and 1B . An exemplary additive manufacturing system  100  includes a vision system  102 , an additive manufacturing machine  104 , and a control system  106  operably configured to control the vision system  102  and/or the additive manufacturing machine  104 . The vision system  102  and the additive manufacturing machine  104  may be provided as a single, integrated unit or as separate stand-alone units. The vision system  102  and the additive manufacturing machine  104  may be operably coupled with one another via a communication interface utilizing wired or wireless communication lines, which may provide a direct connection between the vision system  102  and the additive manufacturing machine  104 . The control system  106  may include one or more control systems  106 . For example, a single control system  106  may be operably configured to control operations of the vision system  102  and the additive manufacturing machine  104 , or separate control systems  106  may be operably configured to respectively control the vision system  102  and the additive manufacturing machine  104 . A control system  106  may be realized as part of the vision system  102 , as part of the additive manufacturing machine  104 , and/or as a stand-alone unit provided separately from the vision system  102  and/or the additive manufacturing machine  104 . A control system  106  may be operably coupled with the vision system  102  and/or the additive manufacturing machine  104  via a communication interface utilizing wired or wireless communication lines, which may provide a direct connection between the control system  106  and the vision system  102  and/or between the control system  106  and the additive manufacturing machine  104 . An exemplary additive manufacturing system  100  may optionally include a user interface  108  and/or a management system  110 . 
     In some embodiments, a first control system  106  may determine an extension segment-CAD model, generate one or more print commands based at least in part on the extension segment-CAD model, and/or transmit the one or more print commands to a second control system  106 , and the second control system  106  may cause the additive manufacturing machine  104  to additively print the extension segments based at least in part on the print commands. The first control system  106  may be realized as part of a vision system  102 , and/or the second control system  106  may be realized as part of the additive manufacturing machine  104 . Alternatively, or in addition, the first control system  106  and/or the second control system  106  may be realized stand-alone units separate from the vision system  102  and/or the additive manufacturing machine  104 . 
     In some embodiments, a first control system  106  may determine and transmit an extension segment-CAD model to a second control system  106 , the second control system  106  may slice the extension segment-CAD model so as to generate one or more print commands and concurrently or subsequently transmit the one or more print commands to a third control system  106 , and the third control system may cause the additive manufacturing machine  104  to additively print the extension segments based at least in part on the one or more print commands. The first control system  106  may be realized as part of a vision system  102 , the second control system  106  may be realized as a stand-alone unit, and the third control system  106  may be realized as part of the additive manufacturing machine  104 . Alternatively, or in addition, the first control system  106  and/or the second control system  106  may be realized as stand-alone units separate from the vision system  102  and/or the additive manufacturing machine  104 . 
     In some embodiments, a control system  106  may determine a pretreatment-CAD model and/or generate one or more pretreatment commands based at least in part on the pretreatment-CAD model. For example, a first control system  106  may determine the pretreatment-CAD model and/or transmit the pretreatment-CAD model to a second control system  106 , and the second control system  106  may generate one or more pretreatment commands based at least in part on the pretreatment-CAD model, and the second control system  106  may also cause the additive manufacturing machine  104  to subject the extension segments to a pretreatment based at least in part on the pretreatment commands. As another example, the first control system  106  may determine and transmit a pretreatment-CAD model to a second control system  106 , the second control system  106  may generate one or more pretreatment commands based at least in part on the pretreatment-CAD model and concurrently or subsequently transmit the one or more pretreatment commands to a third control system  106 , and the third control system may cause the additive manufacturing machine  104  to subject the extension segments to a pretreatment based at least in part on the pretreatment commands. The first control system  106  may be realized as part of a vision system  102 , the second control system  106  may be realized as a stand-alone unit, and the third control system  106  may be realized as part of the additive manufacturing machine  104 . Alternatively, or in addition, the first control system  106  and/or the second control system  106  may be realized as stand-alone units separate from the vision system  102  and/or the additive manufacturing machine  104 . 
     The vision system  102  may include any suitable camera or cameras  112  or other machine vision device that may be operably configured to obtain image data that includes a digital representation of one or more fields of view  114 . Such a digital representation may sometimes be referred to as a digital image or an image; however, it will be appreciated that the present disclosure may be practiced without rendering such a digital representation in human-visible form. Nevertheless, in some embodiments, a human-visible image corresponding to a field of view  114  may be displayed on the user interface  108  based at least in part on such a digital representation of one or more fields of view  114 . 
     The vision system  102  allows the additive manufacturing system  100  to obtain information pertaining to one or more workpieces  116  onto which a pretreatment may be applied and/or onto which one or more extension segments may be respectively additively printed. In particular, the vision system  102  allows the one or more workpieces  116  to be located and defined so that the additive manufacturing machine  104  may be instructed to pretreat the workpiece-interfaces  120  of one or more workpieces with suitably high accuracy and precision and/or to print one or more extension segments on a corresponding one or more workpieces  116  with suitably high accuracy and precision. The one or more workpieces  116  may be secured to a build plate  118  with a workpiece-interface (e.g. a top surface)  120  of the respective workpieces  116  aligned to a build plane  122 . 
     The one or more cameras  112  of the vision system  102  may be configured to obtain two-dimensional or three-dimensional image data, including a two-dimensional digital representation of a field of view  114  and/or a three-dimensional digital representation of a field of view  114 . Alignment of the workpiece-interfaces  120  with the build plane  122  allows the one or more cameras  112  to obtain higher quality images. For example, the one or more cameras  112  may have a focal length adjusted or adjustable to the build plane  122 . With the workpiece-interface  120  of one or more workpieces  116  aligned to the build plane  122 , the one or more cameras may readily obtain digital images of the workpiece-interfaces  120 . The one or more cameras  112  may include a field of view  114  that that encompasses all or a portion of the one or more workpieces  116  secured to the build plate  118 . For example, a single field of view  114  may be wide enough to encompass a plurality of workpieces  116 , such as each of a plurality of workpieces secured to a build plate  118 . Alternatively, a field of view  114  may more narrowly focus on an individual workpiece  116  such that digital representations of respective workpieces  116  are obtained separately. It will be appreciated that separately obtained digital images may be stitched together to obtain a digital representation of a plurality of workpieces  116 . In some embodiments, the camera  112  may include a collimated lens configured to provide a flat focal plane, such that workpieces or portions thereof located towards the periphery of the field of view  114  are not distorted. Additionally, or in the alternative, the vision system  102  may utilize a distortion correction algorithm to address any such distortion. 
     Image data obtained by the vision system  102 , including a digital representation of one or more workpieces  116  may be transmitted to the control system  106 . The control system  106  may be configured to determine a workpiece-interface  120  of each of a plurality of workpieces  116  from one or more digital representations of one or more fields of view  114  having been captured by the vision system  102 , and then determine one or more coordinates of the workpiece-interface  120  of respective ones of the plurality of workpieces  116 . Based on the one or more digital representations, the control system  106  may generate one or more print commands and/or one or more pretreatment commands, which may be transmitted to an additive manufacturing machine  104  such that the additive manufacturing machine  104  may additively print a plurality of extension segments on respective ones of the plurality of workpieces  116  and/or subject the plurality of workpieces  116  to a pretreatment prior to additively printing the plurality of extension segments thereon. The one or more print commands may be configured to additively print a plurality of extension segments with each respective one of the plurality of extension segments being located on the workpiece-interface  120  of a corresponding workpiece  116 . The pretreatment commands may be configured to expose the workpiece-interfaces  120  of the workpieces  116  to a pretreatment so as to prepare the workpiece-interfaces  120  for additively printing extension segments thereon. 
     The additive manufacturing machine  104  may utilize any desired additive manufacturing technology. In an exemplary embodiment, the additive manufacturing machine may utilize a powder bed fusion (PBF) technology, such as direct metal laser melting (DMLM), electron beam melting (EBM), selective laser melting (SLM), directed metal laser sintering (DMLS), or selective laser sintering (SLS). The additive manufacturing machine  104  may include any such additive manufacturing technology, or any other suitable additive manufacturing technology may also be used. By way of example, using a powder bed fusion technology, respective ones of a plurality of extension segments may be additively printed on corresponding respective ones of a plurality of workpieces  116  in a layer-by-layer manner by melting or fusing a layer of powder material to the workpiece-interface  120 . In some embodiments, a component may be additively printed by melting or fusing a single layer of powered material to the workpiece-interface  120 . Additionally, or in the alternative, subsequent layers of powder material may be sequentially melted or fused to one another. The pretreatment may be applied using the same additive manufacturing machine  104  utilized to additively print the extension segments. 
     Still referring to  FIGS. 1A and 1B , an exemplary additive manufacturing machine  104  includes a powder supply chamber  124  that contains a supply of powder  126 , and a build chamber  128 . A build plate  118  having one or more workpieces  116  secured thereto may be positioned in the build chamber  128 , where the workpieces  116  may be additively printed in a layer-by-layer manner. The powder supply chamber  124  includes a powder piston  130  which elevates a powder floor  132  during operation of the system  100 . As the powder floor  132  elevates, a portion of the powder  126  is forced out of the powder supply chamber  124 . 
     A recoater  134 , such as a roller or a blade, pushes some of the powder  126  across a work surface  136  and onto a build platform  138 . The build plate  118  may be secured to the build platform  138  with a chuck system  140  in a manner configured to position the build plate  118  on the build platform  138  and/or within the build chamber  128  with sufficiently high accuracy and precision. The workpieces  116  may be secured to the build plate  118  prior to securing the build plate  118  to the build platform  138 . The recoater  134  fills the build chamber  128  with powder  126  and then sequentially distributes thin layers of powder  126  across a build plane  122  near the top of the workpieces  116  to additively print sequential layers of the workpieces  116 . For example, the thin layers of powder  126  may be about 10 to 100 microns thick, such as about 20 to 80 μm thick, such as about 40 to 60 μm thick, or such as about 20 to 50 μm thick, or such as about 10 to 30 μm thick. The build plane  122  represents a plane corresponding to a next layer of the workpieces  116  to be formed from the powder  126 . 
     To form a layer of an extension segment on the workpiece  116  (e.g., an interface layer or a subsequent layer), an energy source  142  directs an energy beam  144  such as a laser or an electron beam onto the thin layer of powder  126  along the build plane  122  to melt or fuse the powder  126  to the top of the workpieces  116  (e.g., to melt or fuse a layer to the workpiece-interfaces  120  and/or melt or fuse subsequent layers thereto). A scanner  146  controls the path of the energy beam  144  so as to melt or fuse the portions of the powder  126  layer that are to become melted or fused to the workpieces  116 . Typically, with a DMLM, EBM, or SLM system, the powder  126  is fully melted, with respective layers being melted or re-melted with respective passes of the energy beam  144 . Conversely, with DMLS, or SLS systems, layers of powder  126  are sintered, fusing particles of powder  126  with one another generally without reaching the melting point of the powder  126 . After a layer of powder  126  is melted or fused to the workpieces  116 , a build piston  148  gradually lowers the build platform  138  by an increment, defining a next build plane  122  for a next layer of powder  126  and the recoater  134  to distributes the next layer of powder  126  across the build plane  122 . Sequential layers of powder  126  may be melted or fused to the workpieces  116  in this manner until the additive printing process is complete. 
     The extension segments may be additively printed on the workpiece-interfaces  120  of respective workpieces  116  at an energy density selected so as to provide a proper bond between the workpiece-interface  120  and the layers of melted or fused powder  126  that form the extension segment  206 . As used herein, the term “energy density” refers to the volumetric energy density E, which may have units of Joules per cubic millimeter (J/mm 3 ) and may be described according to equation (1) as follows: 
     
       
         
           
             
               
                 
                   
                     E 
                     = 
                     
                       
                         P 
                         
                           v 
                           · 
                           h 
                           · 
                           t 
                         
                       
                       ⁢ 
                       
                         k 
                         o 
                       
                       ⁢ 
                       
                         k 
                         r 
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     where P is the power of the energy beam  144  in watts (W), v is the scan speed of the energy beam  144  in millimeters per second (mm/s), h is the hatch spacing between adjacent scan path passes in millimeters (mm), t is the incremental layer thickness in millimeters (mm) as indicated by the incremental amount of lowering of the build platform  138  between sequential layers of powder applied across the build plane  122 , k o  is an overlap constant corresponding to the amount of overlap between adjacent scan path passes, and k r  is a remelt constant corresponding to the amount of remelt between adjacent layers. 
     Variations of the parameters affecting energy density may greatly influence additive printing quality, and in some embodiments the energy density and/or various parameters thereof that may be suitable for forming an original component may be unsuitable for additively printing an extension segment on a pre-existing workpiece  116 . For example, the energy density used to additively print an extension segment on a pre-existing workpiece  116  may be substantially greater than a typical energy density used to additively print an original component. The energy density may be substantially greater, for example, to achieve a desired porosity of the extension segment. The porosity may be described with reference to relative density according to equation (2) as follows: 
     
       
         
           
             
               
                 
                   
                     
                       ρ 
                       ret 
                     
                     = 
                     
                       
                         ρ 
                         * 
                       
                       
                         ρ 
                         s 
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     where ρ* is the density of the additively printed material, and ρ s  is the density of the raw material used. 
     Post-processing such as heat treatment applied to the workpiece  116  and/or exposure to high temperature operating conditions may modify the relative density of the workpiece  116  (e.g., through grain growth, precipitates, twinning, etc.) from that which existed when the workpiece  116  was originally formed. The energy density of the energy beam  144  may be selected so as to provide an extension segment having a relative density, crystal structure, or other properties corresponding to that of the workpiece  116 , such as after accounting for effects of such post-processing or operating conditions on the workpiece  116 . For example, it may be undesirable to subject a component formed by additively printing the extension segment on a workpiece  116  to certain post processing such as heat treatment because the workpiece  116  may have already been subjected to such post processing. As a result, it may be desirable for the additive printing process to provide extension segments having a desired relative density, crystalline structure, and so forth without contribution from post-processing such as heat treatment. 
     In some embodiments, the relative density of an extension segment may be selected so as to substantially match the relative density of a workpiece  116  and/or so as to be equal to or greater than the relative density of the workpiece  116 . In some embodiments the relative density of the extension segment may be substantially greater than the relative density of the workpiece. By way of example, an extension segment may have a relative density of from about 0.950 to 0.9999, such as from 0.970 to 0.9999, such as from 0.990 to 0.9999, such as from 0.997 to 0.9999, such as at least 0.990, such as at least 0.995, such as at least 0.997, such as at least 0.998, such as at least 0.9990, such as at least 0.9995, such as at least 0.9997, such as at least 0.9998, such as at least 0.9999. In some embodiments, an extension segment may exhibit a first relative density and a workpiece may exhibit a second relative density, in which the first relative density exceeds the second relative density by from about 10 to about 100 thousandths, such as from about 10 to about 80 thousandths, such as from about 10 to about 60 thousandths, such as from about 10 to about 40 thousandths, such as from about 10 to about 20 thousandths, such as from about 20 to about 80 thousandths, such as from about 40 to about 80 thousandths, such as from about 60 to about 100 thousandths. 
     To achieve such a relative density, the energy density used to additively print an extension segment on a pre-existing workpiece  116  may be substantially greater than a typical energy density values. For example, whereas typical energy density values may range from about 20 J/mm 3  to about 70 J/mm 3 , exemplary energy density values used to additively print an extension segment on a workpiece  116  may range from about 20 J/mm 3  to about 200 J/mm 3 , such as from about 70 J/mm 3  to about 200 J/mm 3 , such as from about 80 J/mm 3  to about 200 J/mm 3 , such as from about 100 J/mm 3  to about 160 J/mm 3 , such as from about 120 J/mm 3  to about 140 J/mm 3 , such as from about 140 J/mm 3  to about 180 J/mm 3 , such as from about 160 J/mm 3  to about 200 J/mm 3  Such energy density may be at least about 20 J/mm 3 , such as at least about 50 J/mm 3 , such as at least about 70 J/mm 3 , such as at least about 100 J/mm 3 , such as at least about 120 J/mm 3 , such as at least about 140 J/mm 3 , such as at least about 160 J/mm 3 . Such energy density may be less than about 200 J/mm 3 , such as less than about 160 J/mm 3 , such as less than about 140 J/mm 3 , such as less than about 120 J/mm 3 . For example, in some embodiments, the foregoing energy density values may be achieved when the product of k o  and k r  is about 1.0, such as from about 0.2 to about 2.0, such as from about 0.5 to about 1.5, or such as from about 0.8 to about 1.2. 
     In some embodiments, the workpieces  116  (e.g., the workpiece-interfaces  120 ) may be subjected to a pretreatment, which may be performed with and/or without powder  126  applied to the workpiece-interface  120 . To perform a pretreatment, an energy source  142  directs an energy beam  144  such as a laser or an electron beam onto the workpiece-interface  120  and/or a thin layer of powder  126  along the build plane  122 . The pretreatment may be performed at an energy density selected so as to provide the desired effect of the pretreatment, such as additive-leveling, melt-leveling, and/or heat conditioning. When the pretreatment is performed with powder  126  applied to the workpiece-interface  120 , the energy density may be described according to equation (1) above. When the pretreatment is performed without powder  126 , such as in the case of a melt-leveling pretreatment and/or a heat-conditioning pretreatment, the energy density may be described according to equation (1), where t equals 1. Variations of the parameters affecting energy density may also greatly influence the character and effect of the pretreatment, and in some embodiments the energy density and/or various parameters thereof that may be suitable for forming an original component or for printing an extension segment on a pre-existing workpiece may be unsuitable for pretreatment. For example, in some embodiments the energy density used to pretreat a workpiece-interface  120  may be substantially lower than a typical energy density used to additively print an original component and/or an extension segment. For example, some heat-conditioning pretreatments may be performed at an energy density that does not generate a melt pool. In some embodiments, a workpiece-interface may be pretreated using a first energy density that is from about 10% to about 100% of a second energy density used to additively print an extension segment on the workpiece-interface, such as a first energy density that is from about 10% to about 90% of the second energy density, such as a first energy density that is from about 10% to about 70% of the second energy density, such as from about 20% to about 50% of the second energy density, such as from about 40% to about 80% of the second energy density, or such as from about 60% to about 90% of the second energy density. Such first energy density and/or such second energy density may be utilized for all or a portion of the respective pretreatment or additive-printing operation. 
     However, in other embodiments an energy density used to pretreat a workpiece-interface may be comparable to an energy density used to additively print an extension segment on a workpiece  116 . For example, in some embodiments, an additive-leveling pretreatments and/or a melt-leveling pretreatments may be performed at an energy density comparable to an energy density used to additively print an extension segment on the pretreated workpiece-interface. However, in other embodiments, an additive-leveling pretreatments and/or a melt-leveling pretreatments may be performed at an energy density that differs significantly from an energy density used to print an extension segment on the pretreated workpiece-interface. For example, an energy density used to perform an additive-leveling pretreatment and/or a melt-leveling pretreatment may be selected so as to provide a desired relative density at or near the workpiece-interface of the workpiece. For example, an energy density may be selected for the additive-leveling pretreatment and/or the melt-leveling pretreatment so as to provide a graduated relative density that transitions from a first relative density of the workpiece to a second relative density of the workpiece-interface. 
     In still further embodiments, the energy density selected for a pretreatment such as an additive-leveling pretreatment and/or a melt-leveling pretreatment may be significantly greater than the energy density selected for additively printing an extension segment on the pretreated workpiece-interface. For example, some aberrant features may be more effectively remediated using an energy density that is significantly higher than suitable energy density values for additively-printing an extension segment on the pretreated workpiece-interface. In some embodiments, a workpiece-interface may be pretreated using a first energy density that is from about 100% to about 300% of a second energy density used to additively print an extension segment on the workpiece-interface, such as a first energy density that is from about 110% to about 300% of the second energy density, such as a first energy density that is from about 110% to about 200% of the second energy density, such as from about 110% to about 150% of the second energy density, such as from about 150% to about 200% of the second energy density, or such as from about 200% to about 300% of the second energy density. Such first energy density and/or such second energy density may be utilized for all or a portion of the respective pretreatment or additive-printing operation. 
     In various embodiments, the pretreatment may be performed without powder  126  applied across the workpiece-interface  120 , while in other embodiments a thin layer of powder  126  may be applied across all or a portion of the workpiece-interface  120 . The energy beam  144  may follow a tool path in a manner generally similar to a scan path followed when additively printing on a workpiece-interface; however, the energy beam  144  may exhibit a different characteristic and/or may achieve a different effect as compared to additively printing depending on the objectives of the pretreatment. 
     Regardless of whether or not there is powder  126  applied across the workpiece-interface  120 , the energy beam may generate a melt pool path and/or a heat treatment path across the workpiece-interface  120 . The pretreatment may prepare the workpiece-interface  120  for subsequently additively printing thereon, for example, by remediating aberrant features of the workpiece  116  and/or of the workpiece-interface  120  and/or by enhancing one or more features of the workpiece  116  and/or of the workpiece-interface  120  in preparation for additively printing an extension segment on the workpiece-interface  120 . A workpiece  116  and/or a workpiece-interface  120  that includes one or more aberrant features may sometimes be referred to respectively as an aberrant workpiece  116  or an aberrant workpiece-interface  120 . By way of example, an aberrant workpiece-interface  120  may be at least partially askew relative to the build plane  122 . Additionally, or in the alternative, an aberrant workpiece-interface  120  may include one or more regions that differ in elevation relative to the build plane  122  and/or relative to one another, and/or that are at least partially askew relative to one another. As further example, an aberrant workpiece  116  or workpiece-interface  120  may include oxidation, contaminants, debris, subtractive modification artifacts (e.g., grooves, scratches, burrs, etc.), incongruent or undesirable grain structures and/or grain sizes, dislocations, microcracks, and/or voids. 
     The pretreatment may remediate such aberrant features and/or enhance one or more features. For example, in some embodiments, the pretreatment may by level the workpiece-interface  120  through melt-leveling and/or additive-leveling. Additionally, or in the alternative, the pretreatment may remove oxidation, contaminants, debris, and/or subtractive modification artifacts (e.g., grooves, scratches, burrs, etc.) from the workpiece-interface  120 . The pretreatment may include melt-leveling and/or additive-leveling. Additionally, or in the alternative, the pretreatment may include heat-conditioning. 
     A pretreatment that includes melt-leveling pretreatment may include using the energy beam to generate a melt pool across at least a portion of the workpiece-interface  120 . A pretreatment that includes additive-leveling may include applying powder  126  across at least a portion of the workpiece-interface  120  and melting or fusing the powder  126  to at least a portion of the workpiece-interface, such as at one or more regions of the workpiece-interface having a lower elevation relative to the build plane  122  and/or relative to one or more other regions of the workpiece-interface. It will be appreciated that a pretreatment may include additive-leveling and/or melt-leveling, individually or in combination. For example, a first region of the workpiece-interface  120  may be subjected to melt-leveling and a second region of the workpiece-interface  120  may be subjected to additive leveling. Additionally, or in the alternative, at least a portion of a workpiece interface  120  may be subjected to melt leveling followed by additive-leveling. 
     A pretreatment that includes heat-conditioning may include generating a heat-treatment scan path and/or a melt-pool scan path across at least a portion of the workpiece-interface. The heat-treatment scan path and/or a melt-pool scan path heat-conditioning pretreatment may include modifying the grain structure of the workpiece  116  at or near the workpiece-interface  120 , for example, remediating aberrant grain structures and/or grain sizes, dislocations, microcracks, and/or voids. Heat-conditioning may also include enhancing grain structures and/or grain sizes, for example, providing a more uniform grain structure and/or a grain structure with enhanced hardness, tensile strength and/or ductility properties, providing a smaller or larger grain size, changing grain size distribution, and/or providing a grain size or distribution with enhanced hardness, tensile strength, and/or ductility properties. Such a heat-conditioning pretreatment may be provided concurrently with or as a result of melt-leveling or additive-leveling. Additionally, or in the alternative, a heat-conditioning pretreatment may be provided separately from a melt-leveling or additive-leveling pretreatment. A pretreatment may include heat-conditioning individually or in combination with melt-leveling and/or additive-leveling. 
     A pretreatment that includes additive-leveling may include applying one or more layers of powder  126  across the workpiece-interface  120  and using the energy beam  144  to melt or fuse the powder  126  to the top of the workpieces  116  (e.g., to melt or fuse a layer to the workpiece-interfaces  120  and/or melt or fuse subsequent layers thereto) similarly to additively printing an extension segment  206  on the workpiece  116 . However, the characteristic and/or the effect of powder  126  melted or fused to a workpiece  116  as part of a pretreatment may be distinguished from the characteristic and/or the effect of powder  126  melted or fused to a workpiece  116  as part of additively printing an extension segment  206  on the workpiece  116 . For example, in some embodiments, the powder  126  used for the pretreatment may have a different composition from the powder  126  used for additively printing an extension segment  206 . Additionally, or in the alternative, in some embodiments, the energy beam  144  may provide a higher or lower energy density during the pretreatment relative to the energy density used when additively printing the extension segment  206 . The one or more powder  126  layers melted or fused to the workpiece-interface during the pretreatment may be provided so as to additively-level the workpiece-interface and/or to provide desirable metallurgical properties across the workpiece-interface  120 . The one or more powder  126  layers may be applied to all or a portion of a workpiece-interface  120 , and a pretreatment command may be configured to melt or fuse the powder  126  to all or a portion of the workpiece-interface  120 . Such characteristics and/or effects of pretreatment may improve bonding between the workpiece  116  and an extension segment  206  additively printed on the workpiece following pretreatment. Additionally, or in the alternative, such characteristics and/or effects of pretreatment may improve the precision and/or accuracy with which an extension segment  202  may be additively printed on a workpiece  116 . 
     In some embodiments, when an aberrant workpiece-interface  120  exhibits skewness and/or differing elevations relative to the build plane  122  and/or relative to various regions, the skewness or differing elevation may range from about 1 micrometer (μm) to about 500 μm. For example, a first region of the workpiece-interface  120  may exhibit skewness and/or a differing elevation relative to the build plane  122  and/or relative to a second region of the workpiece-interface  120 , such as from about 1 micrometer (μm) to about 500 μm, such as from about 25 μm to about 400 μm, such as from about 50 μm to about 250 μm, or such as from about 75 μm to about 150 μm, such as at least 10 μm, such as at least 25 μm, such as at least 50 μm, such as at least 75 μm, such as at least 150 μm, such as at least 250 μm, or such as at least 400 μm. Regardless of whether the pretreatment includes additive-leveling or melt-leveling, the pretreatment may at least partially level the workpiece-interface  120 , reducing such skewness and/or differences in elevation. For example, skewness and/or a difference in elevation of an aberrant workpiece-interface  120  may be reduced by from 50% to 100%, such as from 75% to 100%, such as from 90% to 100%. A pretreatment may level the workpiece-interface  120 , for example, as between a first region of the workpiece-interface  120  to a second region of the workpiece-interface  120 , to from about 1 μm to about 75 μm, such as from about 1 μm to about 50 μm, such as from about 1 μm to about 25 μm, such as from about 1 μm to about 10 μm. 
     Still referring to  FIGS. 1A and 1B , to perform a pretreatment, a scanner  146  controls the path of the energy beam  144  so as to melt or heat at least a portion of the workpiece-interface  120  and/or to melt or fuse at least portions of the powder  126  layer to the workpiece-interface  120 . In some embodiments, after a layer of powder  126  is melted or fused to the workpieces  116 , a build piston  148  gradually lowers the build platform  138  by an increment, defining a next build plane  122  for a next layer of powder  126 , and the recoater  134  may then distribute the next layer of powder  126  across the next build plane  122 . Sequential layers of powder  126  may be melted or fused to the workpieces  116  in this manner until the pretreatment process is complete. 
     Now referring to  FIGS. 2A and 2B , an exemplary workpiece-assembly  200  that includes a plurality of workpieces  116  secured to a build plate  118  is shown. The build plate  118  may be configured to align the workpieces  116  to respective registration points  202 . The registration points  202  may be mapped to a coordinate system.  FIG. 2A  shows a workpiece-assembly  200  that includes a plurality of workpieces  116  secured to a build plate  118 . The arrangement depicted in  FIG. 2A  reflects a point in time prior to additively printing extension segments  206  onto the workpiece-interfaces  120 .  FIG. 2B  shows the workpiece-assembly  200  of  FIG. 2A  but reflecting a point in time after an additive printing process. As shown in  FIG. 2B , a plurality of components  204  are secured to the build plate  118 , which were formed during the additive printing process by additively printing respective ones of a plurality of extension segments  206  onto respective ones of the plurality of workpieces  116 . 
     The build plate  118  and/or workpiece-assembly  200  shown in  FIGS. 2A and 2B  may be used to facilitate additively printing an extension segment  206  on a workpiece  116 , including additively printing respective ones of a plurality of extension segments  206  on respective ones of a plurality of workpieces  116  as part of a single build. In some embodiments, a build plate  118  may be configured to align the workpieces  116  to respective registration points  202  so as to facilitate image capture by the vision system  102 , so as to facilitate alignment of CAD models with the workpieces  116  (e.g., so that extension segments  206  as defined by a CAD model may be properly additively printed on the workpieces  116 ), and/or so as to facilitate operability of the additive manufacturing machine  104 . 
     The workpiece-assembly  200  shown in  FIGS. 2A and 2B  may hold any number of workpieces  116 . As one example, the workpiece-assembly  200  shown may hold up to 20 workpieces  116 . As another example, a workpiece-assembly  200  may be configured to hold from 2 to 100 workpieces  116 , or more, such as from 2 to 20 workpieces  116 , such as from 10 to 20 workpieces  116 , such as from 20 to 60 workpieces  116 , such as from 25 to 75 workpieces  116 , such as from 40 to 50 workpieces  116 , such as from 50 to 100 workpieces  116 , such as from 5 to 75 workpieces  116 , such as from 75 to 100 workpieces  116 , such as at least 2 workpieces  116 , such as at least 10 workpieces  116 , such as at least 20 workpieces  116 , such as at least 40 workpieces  116 , such as at least 60 workpieces  116 , or such as at least 80 workpieces  116 . 
     In some embodiments, for example, when the workpieces  116  are airfoils such as compressor blades or turbine blades of a turbomachine, the workpiece-assembly  200  may be configured to hold a number of blades that corresponds to the number of blades in one or more stages of the compressor and/or turbine, as applicable. In this way, all of the blades of a given one or more stages of a turbine and/or compressor may be kept together and extension segments  206  may be additively printed thereon in one single build. It will be appreciated that the workpiece-assembly  200  and build plate  118  reflect one exemplary embodiment, which is provided by way of example and not to be limiting. Various other embodiments of a workpiece-assembly  200  and/or build plate  118  are contemplated which may also allow for the workpieces  116  to be secured with suitable positioning and alignment, all of which are within the spirit and scope of the present disclosure. 
     The exemplary workpiece-assembly  200  shown in  FIGS. 2A and 2B  includes a build plate  118  with one or more workpiece bays  208  disposed therein. Each of the one or more workpiece bays  208  may include one or more workpiece docks  210 . The one or more workpiece bays  208  may additionally include one or more clamping mechanisms  212  which operate to secure one or more workpieces  116  to the build plate  118 . The one or more workpiece docks  210  may be configured to receive one or more workpiece shoes  214 , and the one or more workpiece shoes  214  may be respectively configured to receive a workpiece  116 . The one or more clamping mechanisms  212  may be configured to clamp the workpiece shoes  214  in position within the corresponding workpiece docks  210 . 
     A workpiece dock  210  and/or a workpiece shoe  214  may include one or more biasing members (not shown) configured to exert a biasing force (e.g., an upward or vertical biasing force) between the workpiece shoe  214  and the build plate  118  such as the bottom of the workpiece dock  210 . The biasing members may include one or more springs, one or more magnet pairs (e.g. permanent magnets or electromagnets), one or more piezoelectric actuator, or the like operable to exert such a biasing force. The biasing force exerted by the biasing members biases the workpiece shoe  214  so as to allow the workpiece-interfaces  120  (e.g., the top surfaces of the workpieces  116 ) to be aligned with one another. By way of example, an alignment plate (not shown) may be placed on top of the workpieces  116  so as to partially compress the biasing members and bring the workpiece-interfaces  120  (e.g., the top surfaces of the workpieces  116 ) into alignment with one another. In some embodiments, elevating blocks (not shown) may be placed between the build plate  118  and the alignment plate (not shown) to assist in positioning the alignment plate on top of the workpieces  116  at a desired height. With the workpiece-interfaces  120  aligned with one another, the clamping mechanism  212  may be tightened so as to secure the workpieces  116  to the build plate  118 . 
     As shown in  FIGS. 3A and 3B , a misalignment of workpieces  116  from the build plane  122  may introduce printing failures.  FIG. 3A  shows a plurality of workpieces  116 , including a first workpiece  300  situated in alignment with the build plane  122 , a second workpiece  302  situated below the build plane  122 , and a third workpiece  304  situated above the build plane  122 . When the recoater  134  distributes powder  126  across the build plane  122 , the first workpiece  300  would generally be expected to receive an appropriately thick layer of powder  126  across the top portion thereof. By contrast, the second workpiece  302  and the third workpiece  304  illustrate misalignments from the build plane  122  which may likely cause printing failures. For example, the second workpiece  302  may exhibit printing failures attributable to an overly thick layer  306  of powder  126 , such as insufficient bonding of the powder  126  layer to the second workpiece  302 . Such insufficient bonding may be caused by incomplete melting of the powder  126  or the top layer (e.g., the workpiece-interface  120 ) of the second workpiece  302 , as well as voids formed from gasses trapped within the layer that with adequate melting generally would be eliminated. As another example, the third workpiece  304  may exhibit printing failures attributable to the surface  308  of the third workpiece  304  protruding above the build plane  122 , such that the recoater  134  may skip over the protruding surface  308  of the third workpiece  304  and/or such that the recoater  134  may become obstructed by the third workpiece, damaging the recoater  134  or preventing the recoater  134  from moving past the protruding surface  308 . 
     In some embodiments, even if a mis-aligned workpiece  116  does not cause a total printing failure such as obstructing the recoater  134 , the misalignment may cause variations in melting, dimensional inaccuracy, microhardness, tensile properties, and/or material density. These variations may propagate as sequential layers are added to the workpieces  116 . Additionally, components  204  with such variations may fail during operation, potentially causing damage to other equipment including catastrophic failures. For example, if a compressor blade or turbine blade fails, the failure may damage other portions of the turbomachine potentially rendering the turbomachine immediately inoperable. 
     However, as shown in  FIGS. 3C and 3D , the present disclosure provides a build plate  118  and/or workpiece-assembly  200  configured to at least partially align the top portions of a plurality of workpieces  116  with a build plane  122 . A pretreatment may then be applied to the plurality of workpieces  116  to further align the workpiece-interfaces  120  to the build plane  122 . In an exemplary embodiment, the top portion of a workpiece  116  provides a workpiece-interface  120 , which workpiece-interface  120  may be prepared at least in part by performing a subtractive modification to the workpiece  116 . Such workpiece-interfaces  120  may include a surface, a plane, a tip, or the like generally corresponding to the highest or tallest portion of the workpiece  116  when loaded into the build plate  118 . With the top portions aligned by the workpiece-assembly  200 , a plurality of extension segments  206  may be additively printed on a corresponding plurality of workpieces  116  together in a common build using a powder bed fusion process while assuring that the recoater  134  may apply uniform layers of powder  126  across each of the workpieces  116 . In some embodiments, the build plate  118  may be capable of aligning a plurality of workpieces  116  to a build plane  122  within a tolerance of 100 microns or less, such as 80 μm or less, such as 60 μm or less, such as 40 μm or less, such as 20 μm or less, or such as 10 μm or less. 
     The alignment provided by the workpiece-assembly  200  may compensate for differences in the size of respective workpieces  116 . Such differences in size may be attributable to workpieces  116  having variations in size arising from any source, including the workpieces  116  having a different original configuration, and/or the workpieces  116  having variations in size arising from a subtractive modification performed to prepare a workpiece-interface  120  on the workpieces  116 . In some embodiments, for example, when the workpieces  116  are airfoils of a turbomachine, such as compressor blades and/or turbine blades, such airfoils from different stages of the turbomachine may be secured within a workpiece-assembly  200  with the respective workpiece-interfaces  120  (e.g., the top surfaces of the workpieces  116 ) aligned with one another even though the respective workpieces  116  may have different sizes relative to one another. 
     Now referring to  FIG. 4 , an exemplary method  400  of additively printing an extension segment  206  on a workpiece-interface  120  of a workpiece  116  will be described. The exemplary method may be performed by an additive manufacturing system  100  as described herein, such as using a control system  106  communicatively coupled to a vision system  102  and an additive manufacturing machine  104 . An exemplary method  400  includes, at step  402 , determining a workpiece-interface  120  from a digital representation of a field of view  114  having been captured by a vision system  102 . Determining the workpiece  116  may include determining a workpiece-interface  120 . For example, the exemplary method may include determining a workpiece-interface  120  of each of a plurality of workpieces  116  from one or more digital representations of one or more fields of view  114  having been captured by a vision system  102 . Determining the workpiece-interface  120  may include determining one or more coordinates of the workpiece-interface  120 , for example, of respective ones of the plurality of workpieces  116 . The one or more fields of view  114  may include one or more workpieces situated in three-dimensional space, such as a two-dimensional field of view  114  or a three-dimensional field of view  114 . For example, the one or more fields of view  114  may include a two-dimensional or three-dimensional top view of one or more workpieces  116  individually and/or of a plurality of workpieces  116  collectively, such as a two-dimensional or three-dimensional top view of the workpiece-interface  120  of one or more workpieces  116  individually and/or of a plurality of workpieces  116  collectively. 
     In some embodiments, an exemplary method  400  may include, at step  404 , obtaining a digital representation of a field of view  114  using a vision system  102 , where the field of view  114  includes a workpiece-interface  120 . This may include obtaining one or more digital representations of the one or more fields  114  of view using the vision system  102 . Alternatively, an exemplary method  400  may commence with one or more digital representations already having been obtained from the vision system  102 . 
     An exemplary method  400  additionally includes, at step  406 , transmitting to an additive manufacturing machine  104 , a print command configured to additively print an extension segment  206  on a workpiece-interface  120 , with the print command having been generated based at least in part on the digital representation of the field of view  114 . The print command may be configured to additively print the extension segment  206  on a workpiece-interface  120 . One or more print commands may be transmitted to the additive manufacturing machine  104 , and the one or more print commands may be configured to additively print a plurality of extension segments  206  with each respective one of the plurality of extension segments  206  being located on the workpiece-interface  120  of a corresponding respective one of the plurality of workpieces  116 . 
     The one or more print commands may be generated based at least in part on the one or more digital representations of the one or more fields of view  114 . The exemplary method  400  may optionally include, at step  408 , generating a print command based at least in part on a digital representation of a field of view  114  captured by the vision system  102 . This may include generating one or more print commands based at least in part on one or more digital representations of the one or more fields of view  114  that include one or more workpieces  116  and/or one or more workpiece-interfaces  120  thereof. Alternatively, an exemplary method  400  may be performed with one or more print commands already having been generated or having been generated separately, such as by the control system  106  or otherwise. 
     An exemplary method  400  may additionally include, at step  410 , additively printing an extension segment  206  on a workpiece-interface  120  based at least in part on the print command. This may include additively printing respective ones of a plurality of extension segments  206  on corresponding respective ones of a plurality of workpieces  120 , such as on corresponding respective ones of a plurality of workpiece-interfaces  120  thereof. For example, the one or more print commands may be configured to position respective ones of the plurality of extension segments  206  on the workpiece-interface  120  of corresponding respective ones of the plurality of workpieces  116  based at least in part on one or more coordinates of the respective workpiece-interface  120 . 
     In some embodiments, the exemplary method  400  may include exposing a workpiece-interface  120  to a pretreatment, such as using an energy beam  144  from the additive manufacturing machine  104 . An exemplary method  400  may include, at step  412 , transmitting to an additive manufacturing machine  104 , a pretreatment command configured to expose the workpiece-interface  120  to the pretreatment. Step  412  may be performed, for example, after having determined a workpiece-interface  120  at step  402 . The pretreatment command may be generated based at least in part on a digital representation of a field of view  114  having been captured by the vision system  102 . In some embodiments, the exemplary method  400  may optionally include, at step  414 , generating the pretreatment command based at least in part on the field of view  114 . 
     An exemplary method  400  may additionally include, at step  416 , exposing a workpiece-interface  120  to the pretreatment based at least in part on the pretreatment command. This may include exposing respective ones of a plurality of workpiece-interfaces  120  to respective ones of a plurality of corresponding pretreatments. For example, the one or more pretreatment commands may be configured to expose respective ones of the plurality of workpiece-interfaces  120  to a corresponding pretreatment based at least in part on one or more coordinates of the respective workpiece-interface  120 . 
     After having exposed the workpiece-interface  120  to the pretreatment, the exemplary method  400  may proceed with additively printing an extension segment  206  on the workpiece-interface  120 , at step  410 . Alternatively, in some embodiments, after having exposed the workpiece-interface  120  to the pretreatment, the exemplary method  400  may return to step  404 , to obtain a digital representation of a field of view  114  using the vision system  102 , in which the field of view  114  includes a pretreated workpiece-interface  120 . In some embodiments, a digital representation that includes a pretreated workpiece-interface  120  may more suitable for determining a workpiece-interface at step  402 . For example, a pretreated workpiece-interface  120  may allow the vision system  102  to more accurately and/or precisely determine the workpiece-interface  120  at step  402 . This, in turn, may allow for generating a more accurate and/or precise print command at step  408  and/or for more accurately and/or precisely additively printing an extension segment on the workpiece-interface  120  at step  410 . 
     The exemplary method  400  may be performed so as to provide a component  204  by additively printing one or more extension segments  206  onto one or more workpieces  116 . In some embodiments, a plurality of workpieces  116  may include a plurality of blades for a turbomachine, such as compressor blades and/or turbine blades, and the corresponding plurality of extension segments  206  may include a plurality blade tips. The components  204  may be additively printed in a layer-by-layer manner using an additive manufacturing machine  104 . For example, the exemplary method  400  may include additively printing a first layer of a plurality of extension segments  206  on the workpiece-interface  120  of respective ones of the plurality of workpieces  116 , followed by additively printing a second layer of the plurality of extension segments  206  on the first layer of the plurality of extension segments  206 . The first layer may be an interface layer between the workpiece-interface  120  and the extension segment  206  to be additively printed thereon. The second layer may be a subsequent layer of the extension segment  206 . In some embodiments, a component  204  may be additively printed by melting or fusing a single interface layer of powered material to the workpiece-interface  120 . 
     Now referring to  FIGS. 5A-5C , an exemplary workpiece  116  ( FIGS. 5A and 5B ) and an exemplary component  204  ( FIG. 5C ) are shown. The exemplary workpiece  116  and component  204  may be an airfoil such as a compressor blade or a turbine blade, or any other workpiece  116  or component  204 . As shown, the workpiece  116  and component  204  represent a high-pressure compressor blade (HPC-blade) of a turbomachine. The workpiece  116  may be an originally fabricated workpiece, as well as a workpiece  116  being repaired, rebuilt, and so forth. 
     An exemplary method  400  may include subjecting workpieces  116  to a subtractive modification so as to provide a workpiece-interface  120  thereon. This may include cutting, grinding, machining, electrical-discharge machining, brushing, etching, polishing, or otherwise substantively modifying a workpiece  116  so as to provide a workpiece-interface  120  thereon. The subtractive modification may include removing a subtraction portion  500  ( FIG. 5A ), so as to provide a workpiece-interface  120  ( FIG. 5B ). The subtractive modification may include removing at least a portion of a surface of the workpiece  116  that has been worn or damaged. For example, as shown in  FIG. 5A , the workpiece  116  may include artifacts  502 , such as microcracks, pits, abrasions, defects, foreign material, depositions, imperfections, and the like. Such artifacts  502  may commonly appear on the top surface of a compressor or turbine blade as a result of the extreme conditions to which such blades are subjected. The subtractive modification may additionally or alternatively be performed so as to improve bonding between the workpiece  116  and the extension segment  206 . 
     When the workpieces  116  include airfoils for a turbomachine, such as compressor blades and/or turbine blades, as shown in  FIGS. 5A and 5B , the subtractive modification may include removing a tip portion of the airfoils, for example, to remove a worn or damaged area. Alternatively, in some embodiments, a component  204  may initially appear as shown in  FIG. 5B , without requiring a subtractive modification, or without requiring a substantial portion of the component  204  to be removed during the subtractive modification. For example, the workpiece  116  may be an intermediate workpiece  116  in an original fabrication process. 
     The amount of material removed during the subtractive modification may vary depending on the nature of the workpiece  116 , such as how much material needs to be subtracted so as to provide a workpiece-interface  120  and/or to remove worn or damaged material. The amount of material removed may be limited to only a very thin surface layer when the subtractive modification is intended to prepare a workpiece-interface  120  without removing layers of more substantial thickness, or when wear or damage to a workpiece  116  is limited to a thin surface layer. Alternatively, the amount of material removed from a workpiece  116  may include a majority of the workpiece  116 , such as when the workpiece  116  has larger cracks, breaks, or other damage penetrating deeper into the workpiece  116 . 
     In some embodiments, the amount of material removed may be from about 1 micron to 1 centimeter, such as from about 1 μm to about 1,000 μm, such as from about 1 μm to about 500 μm, such as from about 1 μm to about 100 μm, such as from about 1 μm to about 25 μm, such as from about 100 μm to about 500 μm, such as from about 500 μm to about 1,000 μm, such as from about 100 μm to about 5 mm, such as from about 1 mm to about 5 mm, such as from about 5 mm to about 1 cm. In still further embodiments, the amount of material removed may be from about 1 centimeter to about 10 centimeters, such as from about 1 cm to about 5 cm, such as from about 2 cm to about 7 cm, such as from about 5 cm to about 10 cm. 
     Regardless of the nature of the workpiece  116 , as shown in  FIG. 5C , a near net shape component  204  may be formed by additively printing an extension segment  206  on the workpiece  116 . The near net shape component  204  may include an extension segment  206  that is substantially congruent with the workpiece  116  (and/or the workpiece-interface perimeter  504 ), such that the extension segment  206  aligns with the workpiece  116  (and/or the workpiece-interface perimeter  504 ) with sufficient congruency that a near net shape component  204  may be provided without requiring a subsequent subtractive modification apart from surface finishing such as polishing, buffing, and the like. The extension segments  206  may be additively printed on the respective workpiece-interfaces  120  such that the extension segments  206  are substantially congruent with the workpieces  116  and/or the workpiece-interfaces  120 . For example, the workpiece-interface  120  may have a workpiece-interface perimeter  504  ( FIG. 5B ), and the extension segments  206  may be additively printed on the respective workpiece-interfaces  120  such that the extension segment  206  is substantially congruent with the workpiece-interface perimeter  504 . The extension segments  206  may include an interface layer that is substantially congruent with the workpiece-interface  120 , including an interface layer perimeter that is substantially congruent with the workpiece-interface perimeter  504 . In an exemplary embodiment, an extension segment  206  additively printed on a workpiece-interface  120  may be regarded as substantially congruent with the workpiece  116  (and/or the workpiece-interface perimeter  504 ) when the workpiece  116  is an airfoil (e.g., a compressor blade or a turbine blade) having a workpiece-interface  120  in the form of a crescent shape and the extension segment  206  also has a crescent shape determined at least in part based on a digital representation of the workpiece-interface  120  of the workpiece  116 . 
     In some embodiments, as shown in  FIG. 5C , the component  204  may include an overhang  506 , such that the extension segment  206  overhangs the workpiece-interface  120  (e.g., the workpiece-interface perimeter  504 ). Notwithstanding the presence of the overhang  506 , the component  204  may be regarded as a near net shape component  204 , and/or the extension segment  206  may be regarded as being substantially congruent with the workpiece  116  (and/or the workpiece-interface perimeter  504 ), such as when the overhang  506  does not require a subsequent subtractive modification apart from surface finishing such as polishing, buffing, and the like. The purpose of the overhang  506  may be, for example, to leave a small portion of material available for such surface finishing, including polishing, buffing, and the like. The size of the overhang  506  may be selected based on the nature of the finishing processes. After such finishing processes, the overhang  506  may be substantially removed. 
     By way of example, in some embodiments, the overhang  506  may be from about 1 micron to 1,000 microns, such as from about 1 μm to 500 μm, such as from about 1 μm to 100 μm, such as from about 1 μm to 50 μm, such as from about 1 μm to 25 μm, such as from about 10 μm to 50 μm, such as from about 25 μm to 50 μm, such as from about 50 μm to 100 μm, such as from about 50 μm to 250 μm, such as from about 250 μm to 500 μm, such as from about 500 μm to 1,000 μm, such as about 1,000 μm or less, such as about 500 μm or less, such as about 250 μm or less, such as about 100 μm or less, such as about, such as about 50 μm or less, or such as about 25 μm or less. In an exemplary embodiment, the respective ones of a plurality of extension segments  206  may overhang the corresponding workpiece-interface  120  of respective ones of the plurality of workpieces  116  with the overhang  506  having a maximum overhang distance of about 1,500 microns or less, such as about 1,000 μm or less, such as about 500 μm or less, or such as about 100 μm or less or such as about 50 μm or less or such as about 25 μm or less. In some embodiments, an extension segment  206  may be regarded as being substantially congruent with the workpiece  116  and/or the workpiece-interface perimeter  504  when the extension segment  206  includes an overhang  506  having a maximum overhang distance of about 1,500 microns or less, such as about 1,000 μm or less, such as about 500 μm or less, or such as about 100 μm or less or such as about 50 μm or less or such as about 25 μm or less. 
     While a workpiece-interface  120  may be relatively small, the additive manufacturing machine  104  may nevertheless additively print an extension segment  206  thereon so as to provide a near net shape component  204 . For example, as shown in  FIG. 5B , a workpiece  116  may have a workpiece-interface  120  with a cross-sectional width, w, and a height, h w , such that a ratio of the height of the workpiece  116  to the cross-sectional width may be from about 1:1 to 1,000:1, such as from about 1:1 to 500:1, such as from about 1:1 to 250:1, such as from about 1:1 to about 100:1, such as from about 1:1 to about 75:1, such as from about 1:1 to about 65:1, such as from about 1:1 to about 35:1, such as from about 2:1 to about 100:1, such as from about 5:1 to about 100:1, such as from about 25:1 to about 100:1, such as from about 50:1 to about 100:1, such as from 75:1 to about 100:1, such as at least 5:1, such as at least 10:1, such as at least 25:1, such as at least 50:1, such as at least 75:1 such as at least 100:1, such as at least 250:1, such as at least 500:1, such as at least 750:1. 
     As shown in  FIG. 5C , an extension segment  206  may have a height, h e , such that a ratio of the cross-sectional width, w, of the workpiece  116  to the height, h e , of the extension segment  206  may be from about 1:1,000 to about 1,000:1, such as about 1:1,000 to about 1:500, such as about 1:500 to about 1:100, such as about 1:100 to about 1:1, such as about 1:10 to about 1:1, such as about 1:10 to about 10:1, such as about 1:1 to about 1:1,000, such as about 1:1 to about 1:10, such as about 1:1 to 100:1, such as about 1:1 to about 500:1, or such as about 500:1 to about 1,000:1. 
     A ratio of the height, h w , of the workpiece  116  to the height, h e , of an extension segment  206  to may be from about 2:1 to about 10,000:1, such as from about 10:1 to about 1,000:1, such as from about 100:1 to about 10,000:1, such as from about 100:1 to about 500:1, such as from about 500:1 to about 1,000:1, such as from about 1,000:1 to about 10,000:1, such as from about 500:1 to about 5,000:1, such as from about 2,500:1 to about 7,500:1, such as at least 2:1, such as at least 100:1, such as at least 500:1, such as at least 1,000:1, such as at least 5,000:1, or such as at least 7,000:1. 
     In some embodiments, a workpiece  116  may have a cross-sectional width of from about 0.1 millimeters to about 10 centimeters, such as about 0.1 mm to about 5 cm, such as 0.2 mm to about 5 cm, such as about 0.5 mm to about 5 cm, such as about 0.5 mm to about 1 cm, such as about 0.1 mm to about 0.5 mm, such as about 0.1 mm to about 5 mm, such as about 0.5 mm to about 10 mm, such as about 0.5 mm to about 5 mm, such as about 0.5 mm to about 3 mm, such as about 1 mm to about 5 mm, such as about 3 mm to about 10 mm, such as about 1 cm to about 10 cm, such as about 10 cm or less, such as about 5 cm or less, such as about 3 cm or less, such as about 1 cm or less, such as about 5 mm or less, such as about 3 mm or less, such as about 1 mm or less, such as about 0.5 mm or less. In other embodiments, a workpiece  116  may have a relatively larger cross-sectional width, such as from about 1 cm to about 25 cm, such as from about 5 cm to about 15 cm, such as from about 5 cm to about 10 cm, such as at least about 1 cm, such as at least about 5 cm, such as at least about 10 cm, such as at least about 15 cm, or such as at least about 20 cm. 
     In some embodiments, a workpiece  116  may have a height, h w , of from about 0.5 centimes to about 25 centimeters, such as about 0.5 cm to about 5 cm, such as about 0.5 cm to about 3 cm, such as about 1 cm to about 3 cm, such as about 1 cm to about 10 cm, such as about 10 cm to about 15 cm, such as about 15 cm to about 25, such as at least about 0.5 cm, such as at least 1 cm, such as at least 3 cm, such as at least 5 cm, such as at least 1 about 0 cm, such as at least about 20 cm, such as about 25 cm or less, such as about 20 cm or less, such as about 15 cm or less, such as about 10 cm or less, such as about 5 cm or less, such as about 3 cm or less, or such as about 1 cm or less. 
     In some embodiments, an extension segment  206  may have a height, h e , of from about 10 microns to about 20 centimeters, such as about 10 μm to about 1,000 μm, such as about 20 μm to about 1,000 μm, such as about 50 μm to about 500 μm, such as about 100 μm to about 500 μm, such as about 100 μm to about 1,000 μm, such as about 100 μm to about 500 μm, such as about 250 μm to about 750 μm, such as about 500 μm to about 1,000 μm, such as about 1 mm to about 1 cm, such as about 1 mm to about 5 mm, such as about 1 cm to about 20 cm, such as about 1 cm to about 5 cm, such as about 5 cm to about 10 cm, such as about 10 cm to about 20 cm, such as about 20 cm or less, such as about 10 cm or less, such as about 5 cm or less, such as about 1 cm or less, such as about 5 mm or less, such as about 3 mm or less, such as about 1 mm or less, such as about 500 μm or less, such as about 250 μm or less. 
     In exemplary embodiment, a workpiece  116  may have a height, h w , of from about 1 cm to 5 cm, and a cross-sectional width, w, of from about 0.1 mm to about 5 mm, and an extension segment  206  additively printed thereon may have a height, h e , of from about 10 μm to about 5 mm, such as from about 100 μm to about 1 mm, or such as from about 1 mm to about 5 mm. An exemplary workpiece  116  may have a ratio of the height, ha, of the workpiece  116  to the height, h e , of an extension segment  206  of from about 2:1 to about 10,000:1, such as about 2:1 to about 10:1, such as about 10:1 to about 50:1, such as about 50:1 to about 100:1, such as about 100:1 to about 1,000:1, such as about 1,000:1 to 5,000:1, such as about 10:1 to about 10,000:1, such as about 2:1 to about 100:1, such as about 50:1 to about 5,000:1, such as about 100:1 to about 1,000:1, such as about 1,000:1 to about 5,000:1, such as about 1,000:1 to about 10,000:1, such as about 5,000:1 to 1 about 0,000:1, such as at least 2:1, such as at least 10:1, such as at least 50:1, such as at least 100:1, such as at least 500:1, such as at least 1.000:1, such as at least 5,000:1. 
     An exemplary workpiece  116  may have a ratio of the cross-sectional width, w, of the workpiece  116  to the height, h e , of the extension segment  206  of from about 1:50 to about 1,000:1, such as about 1:10 to about 1:1, such as about 1:5 to about 1:1, such as about 1:1 to about 5:1, such as about 5:1 to about 10:1, such as about 10:1 to about 50:1, such as about 50:1 to about 100:1, such as about 100:1 to about 500:1, such as about 500:1 to about 1,000:1, such as about 2:1 to about 1,000:1, such as about 1:2 to about 1:1, such as about 1:1 to 1,000:1, such as about 2:1 to about 10:1, such as about 5:1 to about 500:1, such as about 10:1 to about 100:1, such as about 100:1 to 500:1, such as about 100:1 to 1,000:1, such as about 500:1 to 1,000:1, such as at least 2:1, such as at least 10:1, such as at least 50:1, such as at least 100:1, such as at least 500:1. 
     Referring again to  FIGS. 1A and 1B , exemplary methods of obtaining a digital representation of a field of view  114  using a vision system  102  will be discussed. When the vision system  102  is integrated with the additive manufacturing machine  104 , the vision system  102  may capture digital images of the workpieces  116  with the workpieces  116  secured to the build plate  118 , and the build plate  118  secured to the build platform  138 . The chuck system  140  may position and align the build plate  118  within the build chamber  128  and on the build platform  138  with a high level of precision and accuracy, which also thereby aligns and positions the workpieces  116  within the build chamber  128 . The digital images may also be captured prior to the build plate  118  having been placed in the build chamber  128  and secured to the build platform  138 ; however, generally it will be preferable to take advantage of the positioning and alignment provided by the chuck system  140 . When the vision system  102  is not integrated with the additive manufacturing machine  104 , digital images may be captured before the build plate  118  has been placed in the build chamber  128  and secured to the build platform  138 , such as in the case of a vision system  102  that is provided as a separate unit from the additive manufacturing machine  104 . 
     The digital images of the workpieces  116  may be captured during or after powder  126  has been added to the build chamber  128 . Good contrast between the workpiece-interface  120  and the surrounding portions of the area of interest  600  (and/or between the workpiece-interface perimeter  504  and the surrounding portions of the area of interest  600 ) (e.g.,  FIGS. 6A and 6B ) may improve the performance of the edge detection algorithm. In some embodiments, the digital images may be captured before distributing powder  126  all the way up to the build plane  122  and/or across the workpiece-interfaces  120 . In some embodiments, image capture may be improved by introducing a layer of powder  126  to the build chamber  128  that comes to just below the build plane  122  and/or just below the workpiece-interfaces  120 , which is sometimes referred to as a “scratch coating.” For example, the powder  126  may provide an improved background (e.g., better contrast, less reflection, more uniformity, etc.) that allows the one or more cameras  112  to better focus on the workpiece-interfaces  120 . Additionally, or in the alternative, in some embodiments a layer of powder  126  may be applied across the workpiece-interfaces  120  so as to determine variations in elevation of the respective workpiece-interfaces  120 . For example, a region of a workpiece-interface  120  having a higher elevation may protrude from the elevation of a powder  126  layer, while the powder layer may cover a region of the workpiece-interface  120  having a lower elevation. Such variations in elevation may be utilized when generating pretreatment commands. However, powder  126  covering a portion of a workpiece-interface  120  may obscure the perimeter of the workpiece-interface  120  and thereby may reduce the quality of the digital images and/or may affect the reliability of the control system  106  in determining the respective workpiece-interfaces  120 . 
     In some embodiments, a layer of powder  126  may be added to the build chamber  128  that comes to just below the build plane  122  and/or just below the workpiece-interfaces  120  prior to the digital images of the workpieces  116  being captured. The digital images may be captured with such a layer of powder  126  in place. Any stray powder  126  may be brushed away from the workpiece-interfaces  120  prior to capturing the digital images. After having captured digital images with such a layer of powder  126  just below the build plane  122  and/or just below the workpiece-interfaces  120 , additional powder may be added and additional digital images may be captured to determine variations in elevation of the respective workpiece-interfaces  120  and/or to generate pretreatment commands. In still further embodiments, a skirt (not shown) may be utilized that include slits for the workpiece-interfaces  120  to slip through. The skirt may be placed over the workpieces  116  when secured to the build plate  118 , leaving the workpiece-interfaces  120  exposed for purposes of obtaining digital images, and then the skirt may be removed prior to additive printing. 
     Exemplary digital representations of one or more fields of view  114  captured using the vision system  102  are schematically depicted in  FIGS. 6A and 6B .  FIG. 6A  depicts a digital representation of a field of view  114  that includes one workpiece  116 , and  FIG. 6B  depicts a digital representation of one or more fields of view  114  that includes a plurality of workpieces  116 . The digital representation depicted in  FIG. 6B  may be captured from a single field of view  114 , or a plurality of fields of view  114  maybe stitched together to provide a digital representation of one or more fields of view  114  that includes a plurality of workpieces  116 . 
     As shown in  FIGS. 6A and 6B , a field of view  114  may include an area of interest  600  corresponding to a workpiece-interface  120  and/or a workpiece  116  ( FIG. 6A ) or a plurality of areas of interest  600  respectively corresponding to a plurality of workpiece-interfaces  120  and/or workpieces  116  ( FIG. 6B ). Regardless of whether the field of view  114  includes one or more areas of interest  600 , an area of interest  600  may correspond to an expected location of a workpiece-interface  120  and/or a workpiece  116  within the field of view  114 . The expected location may be determined, for example, based on registration points  202  ( FIGS. 2A and 2B ) mapped to a coordinate system. The control system  106  may be configured to process only one or more areas of interest  600  within a field of view  114  so as to reduce processing time. As shown, the area of interest  600  includes a digital representation of a workpiece  116  situated therein. The field of view  114  shown may reflect a top view of the workpiece  116 , such that the digital representation of the workpiece  116  includes a digital representation of a workpiece-interface  120 , which may include a digital representation of the workpiece-interface perimeter  504 . 
     Now referring to  FIG. 7A , exemplary methods of determining a workpiece  116 , a workpiece-interface  120 , and/or a workpiece-interface perimeter  504  of a workpiece  116  will be discussed. An exemplary method  700  includes, at step  702 , determining an area of interest  600  within the field of view  114 . The area of interest  600  may correspond to an expected location of the workpiece  116 , the workpiece-interface  120 , and/or the workpiece-interface perimeter  504  within the field of view  114 . An area of interest may be determined based at least in part on a mapping of coordinates of the field of view  114  to a registration point  202  for a workpiece  116 . 
     An exemplary method  700  may further include, at step  704 , determining a workpiece-interface perimeter  504  within the area of interest  600 . The workpiece-interface perimeter  504  may be determined using an edge detection algorithm. An exemplary edge detection algorithm may determine the workpiece-interface perimeter  504  by determining pixels within the digital representation of the field of view  114  that have discontinuities, such as changes in brightness or contrast. The workpiece-interface  120  and/or the workpiece  116  may be determined based on the workpiece-interface perimeter  504  determined using the edge detection algorithm. Any suitable edge detection algorithm may be utilized, including first or second order operations. Exemplary edge detection algorithms include a Canny algorithm, a Sobel algorithm, a Prewitt algorithm, a Roberts algorithm, a thresholding algorithm, a differential algorithm, a fuzzy logic algorithm, and so forth. The digital images may also be filtered using edge thinning, a Gaussian filter, or the like. Exemplary edge detection algorithms may determine a workpiece-interface perimeter  504  with sub-pixel accuracy. 
     An exemplary method  700  may include, at step  706 , generating a point cloud  602  corresponding to a workpiece-interface perimeter  504 , a workpiece-interface  120 , and/or a workpiece  116 . The point cloud may include any desired number of points corresponding to the workpiece-interface perimeter  504 , the workpiece-interface  120 , and/or the workpiece  116 . The number of points may be selected based on the desired level of resolution of the point cloud  602 . An exemplary point cloud  602  is shown in  FIGS. 6A and 6B . In some embodiments, as shown in  FIG. 6A , a point cloud  602  may be offset by an offset amount  604  corresponding to an intended overhang distance between the workpiece-interface perimeter  504  and an extension segment  206  to be additively printed thereon. When providing such an offset in the point cloud  602 , the step  706  of generating the point cloud  602  may include determining an offset amount  604  and offsetting the series of points of the point cloud  602  by the offset amount  604 . In some embodiments, the offset amount may vary as between a first point along the perimeter  504  and a second point along the perimeter  504 . For example, the offset amount may be configured to vary according to curvature and/or scan path of the additive manufacturing tool. 
     As discussed with reference to  FIG. 4 , in an exemplary method  400  of additively printing an extension segment  206 , after determining a workpiece-interface  120  from the digital representation of the field of view  114 , the exemplary method  400  may include, at step  406 , transmitting to an additive manufacturing machine  104 , a print command configured to additively print the extension segment  206  on the workpiece-interface  120 , and optionally, the exemplary method  400  may include, at step  408 , generating the print command based at least in part on the field of view  114 . In some embodiments, an exemplary method  400  may include, at step  412 , transmitting to an additive manufacturing machine  104 , a pretreatment command configured to expose the workpiece-interface  120  to the pretreatment, and optionally, the exemplary method  400  may include, at step  414 , generating the pretreatment command based at least in part on the field of view  114 . An exemplary method of generating a print command is described, for example, with reference to  FIG. 7B  through  FIG. 12 . Exemplary pretreatments, exemplary methods of generating a pretreatment command, and exemplary methods of pretreating a workpiece-interface  120 , are described, for example, with reference to  FIGS. 14-19 . 
     In some embodiments, the print command and/or the pretreatment command may be based at least in part on a CAD model, such as an extension segment-CAD model that includes a model of one or more extension segments  206  configured to be additively printed on one or more workpieces  116 , such as on the respective workpiece-interfaces  120 . The exemplary method  400  may include determining an extension segment-CAD model and/or generating an extension segment-CAD model. Additionally, or in the alternative, the step  408  of generating a print command based at least in part on the field of view  114  captured by the vision system  102  may include determining an extension segment-CAD model and/or generating an extension segment-CAD model. Further additionally, or in the alternative, the step  414  of generating a pretreatment command based at least in part on the field of view  114  captured by the vision system  102  may include determining an extension segment-CAD model and/or generating an extension segment-CAD model. 
     Now referring to  FIG. 7B , an exemplary method  750  of generating a print command will be described. The exemplary method  750  may be performed, for example, in connection with step  408  in the exemplary method  400  of additively printing an extension segment  206  shown in  FIG. 4 . An exemplary method  750  may include, at step  752 , determining and/or generating an extension segment-CAD model; at step  754 , slicing the extension segment-CAD model; and at step  756 , determining a scan path and an additive printing area for each slice of the extension segment-CAD model. After determining a scan path and an additive printing area for a slice of the extension segment-CAD model, at step  756 , the exemplary method  750  may proceed with determining, at step  758 , whether there is another slice, and if so, the exemplary method  750  may proceed to step  756 , providing for determining a scan path and an additive printing area for a next slice of the extension segment-CAD model  800  (e.g.,  FIG. 8A ). The exemplary method  750  may end, at step  760 , when there are no additional slices for which a scan path and additive printing area may be determined. The number of slices may depend on the size (e.g., height, thickness) of the extension segment(s) in the extension segment-CAD model, as well as the desired thickness of the layers of powder  126  or other material that may be used to additively print the extension segment(s). 
       FIG. 8A  shows an exemplary extension segment-CAD model  800 . The exemplary extension segment-CAD model  800  may include a model of one or more extension segments  206 . As shown, the extension segment-CAD model  800  includes a plurality of models of extension segments  802 . The models of the extension segments  802  respectively conform to the location and shape of a plurality of corresponding workpieces  116  upon which the plurality of extension segments  206  are to be respectively additively printed. For example, the respective models of an extension segment  802  may be aligned with coordinates that respectively correspond to the registration points  202  of a plurality of workpieces  116  secured to a build plate  118 , and/or the models of the extension segments  802  may include a model-interface  804  that is substantially congruent with the workpiece-interface  120  of the corresponding workpiece  116 . The model-interface  804  may be defined by a model-interface perimeter  806 , and the model-interface perimeter  806  may be substantially congruent with the workpiece-interface perimeter  504  of the respective workpiece  116 . A model of the extension segment  802  may include a height, h e , extending from a model-interface  804  to a top surface  808 . 
     In some embodiments, a plurality of workpieces  116  onto which extension segments  206  are to be printed may differ from one another, and yet the extension segment-CAD model  800  may nevertheless include a model of the plurality of extension segments  802  conforming to the location and shape of respective ones of the plurality of workpieces  116 . The model may include one or more model-interfaces  804  that are substantially congruent with corresponding workpiece-interfaces  120  and/or one or more model-interface perimeter  806  that are substantially congruent with corresponding workpiece-interface perimeters  504 . An extension segment-CAD model  800  may be determined and/or generated based at least in part on a CAD model, such as a library-CAD model selected from a database or CAD model library. The database or CAD model library may include a plurality of library-CAD models from which an extension segment-CAD model  800  may be determined and/or generated. 
     An exemplary library-CAD model is shown in  FIG. 8B . A library-CAD model  850  may include a nominal model of one or more nominal workpieces  116 , components  204 , or extension segments  206 . For example, as shown in  FIG. 8B , the library-CAD model  850  may include a nominal model  852  of one or more components  204  intended to be repaired, rebuilt, and/or upgraded. As shown, the library-CAD model  850  may include a nominal model  852  of a plurality of nominal components  204 . The library-CAD model  850  may alternatively include a single nominal component  204 . Additionally, or in the alternative, the library-CAD model  850  may include one or more nominal models  852  of a nominal extension segment  206 , and/or one or more nominal models  852  of a nominal workpiece  116 . In some embodiments, the CAD model library may include one or more extension segment-CAD models  800 , which may include one or more previously determined and/or previously generated extension segment-CAD models  800  from which subsequent extension segment-CAD models  800  may be determined and/or generated. 
     As shown in  FIG. 8B , a nominal model-interface  854  may be determined from a nominal model  852 . A nominal model-interface  854  may correspond to an expected location of a workpiece-interface  120  of a nominal workpiece  116  associated with the library-CAD model  850 . The nominal model-interface  854  may be defined by a nominal model-interface perimeter  856 , and the nominal model-interface perimeter  856  may or may not be substantially congruent with the workpiece-interface perimeter  504  of the respective workpiece  116 . The nominal model-interface  854  may be located at any z-directional position of the nominal model, including up to a nominal top surface  858  of the nominal model  852 . 
     In some embodiments, a library-CAD model  850  or an extension segment-CAD model  800  may be an actual CAD model from which one or more components  204  were originally fabricated, or the library-CAD model may be a copy or a modified version of a CAD model from which one or more components  204  were originally fabricated. While a library-CAD model  850  may generally correspond to one or more workpieces  116  onto which an extension segment  206  is to be additively printed, the one or more workpieces  116  may differ from their original net shape in varying degrees from one workpiece  116  to the next. A difference from such original net shape may exits, for example, when a workpiece  116  has been deformed or damaged such as from exposure to extreme temperature operating conditions and/or from rubbing or impacts from foreign objects. A difference in original net shape may also exist because of variations in a subtractive modification performed to prepare a workpiece-interface  120  on the workpieces  16 . However, the present disclosure provides for generating extension-segment CAD models  800  that include a plurality of models of extension segments  802  respectively conforming to the location and shape of a plurality of workpieces  116  upon which the plurality of extension segments  206  are to be respectively additively printed based on an extension-segment CAD model  800  and/or the models of the extension segments  802  therein. 
     An exemplary method of generating an extension segment-CAD model  800  is shown in  FIGS. 9A and 9B . As shown in  FIG. 9A , an exemplary method  900  of generating an extension segment-CAD model  800  may be performed for each of a plurality of workpieces  116 . An exemplary method  900  may include, at step  902 , determining in a library-CAD model, a nominal model-interface  854  traversing a nominal model corresponding to a respective one of the plurality of workpieces  116 . The nominal model may include a model of a nominal component  204 , such as a model of a component  204  from which the workpieces  116  may have originated. The workpieces  116  may, however, differ from a component  204  having been additively manufactured according to the nominal model, for example, because of damage or wear incurred by the workpieces  116  as a result of the environment with which the component  204  was used, and/or from a subtractive modification performed to prepare the workpiece  116  for an extension segment  206  to be additively printed thereon. The nominal model may additionally or alternatively include a model of a nominal workpiece, such as a nominal model of a workpiece  116  produced by subjecting a nominal component  204  to a subtractive modification process to provide a workpiece-interface  120 . The nominal model may additionally or alternatively include a model of a nominal extension segment  802 , such as a nominal model of an extension segment  802  corresponding to a nominal workpiece  116 . 
     Determining a nominal model-interface  854  may include determining a plane traversing the library-CAD model at a determined height. The determined height may correspond to a height of an expected location of a workpiece-interface  120  for a nominal workpiece  116 . By way of example, a library-CAD model may include a model of a nominal component  204  corresponding to the workpiece, and the workpiece  116  may have been subjected to a subtractive modification, such as to provide a workpiece-interface  120 . An expected location of a workpiece-interface  120  may be determined based at least in part on the nature of the subtractive modification, such as based on an expected amount of material removed or a resulting change in height of the workpiece  116  as a result of the subtractive modification. 
     Additionally, or in the alternative, the determined height may correspond to a height of a workpiece-interface  120  as determined from a digital representation of the workpiece  116 . The height of a workpiece-interface  120  may be measured based at least in part on one or more dimensions of the workpiece  116  obtained from the digital representation of the workpiece, and a nominal model-interface  854  may be determined based at least in part on the measured height. Additionally, or in the alternative, the height of the workpiece-interface  120  may be measured based at least in part one or more dimensions of a workpiece alignment system  200  captured in a field of view  114 . For example, a height of the workpiece-interface  120  may be determined based at least in part on the height of a workpiece shoe  214 , or based at least in part on a difference between the height of the workpiece-interface  120  and the height of a workpiece shoe  214 , or based at least in part on a difference between the height of the workpiece-interface  120  and the height of the build plate  118 . 
     In some embodiments, a nominal model-interface  854  may be determined using a best-fit algorithm. Determining the nominal model-interface  854  traversing the library-CAD model  850  may include determining a plane traversing the library-CAD model that meets a metric associated with a best-fit algorithm applied with respect to the digital representation of the workpiece-interface  120 . The best-fit algorithm may compare one or more planes traversing the library-CAD model to the digital representation of the workpiece-interface  120  until a compared plane satisfies the best-fit metric. The nominal model-interface  854  may be determined based at least in part on a plane that satisfies the best-fit metric. For example, a plane that satisfies the best-fit metric may be determined to be the nominal model-interface  854 . 
     Still referring to  FIG. 9A , an exemplary method  900  of determining and/or generating an extension segment-CAD model  800  may include, at step  904 , comparing the nominal model-interface  854  of the library-CAD model to a digital representation of the workpiece-interface  120  of the respective ones of the plurality of workpieces  116 . The digital representation may have been previously or concurrently obtained using a vision system  102  that has a field of view  114  including the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . The comparison may be performed using an image matching algorithm. In some embodiments, comparing the nominal model-interface  854  to the digital representation of the workpiece-interface  120  may include, at step  906 , determining whether the nominal model-interface  854  and the digital representation of the workpiece-interface  120  sufficiently match one another. However, in some embodiments a matching step  906  need not be included. 
     When included, a matching step  906  may include comparing one or more coordinates of the nominal model-interface  854  with one or more coordinates of the digital representation of the workpiece-interface  120  and determining one or more differences therebetween. The comparing step  904  may additionally or alternatively include comparing one or more coordinates of the one or more registration points  202  with a corresponding one or more coordinates of the nominal model-interface  854  of the library-CAD model and determining one or more differences therebetween. The registration points  202  may correspond to locations of respective ones of a plurality of workpieces  116  onto which respective ones of a plurality of extension segments  206  are to be additively printed using the additive manufacturing machine  104 . The comparing step  904  and the matching step  906  may be performed separately or together as part of the same step. In some embodiments, the matching step  906  may determine whether there is a partial match, a close match, or no match between the nominal model-interface  854  and the workpiece-interface  120 . Alternatively, the matching step  906  may determine whether there is any match (e.g., at least a partial match), or no match between the nominal model-interface  854  and the workpiece-interface  120 . 
     When the matching step  906  determines that there is at least a partial match between the nominal model-interface  854  and the workpiece-interface  120 , the exemplary method  900  may proceed to step  908 , providing for generating a model of an extension segment  802  based at least in part on the nominal model-interface  854 . Step  908  provides a model of an extension segment  802  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116  such that the model of the extension segment  802  is configured to be additively printed on the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . 
     When the matching step  906  determines that there is not at least a partial match between the nominal model-interface  854  and the workpiece-interface  120 , the exemplary method  900  may return to step  902  so as to determine a different nominal model-interface  854  and to compare the different nominal model-interface  854  to the digital representation of the workpiece-interface  120 . The different nominal model-interface  854  may be selected form the same library-CAD model or a different library-CAD model. 
     In some embodiments, the matching step  906  may include determining whether there is more than a partial match, such as a close match between the nominal model-interface  854  and the workpiece-interface  120 . When the matching step  906  determines that there is a close match between the nominal model-interface  854  and the workpiece-interface  120 , the exemplary method  900  may include, at step  910 , selecting the nominal model-interface  854  and/or at least a three-dimensional portion of the nominal model from the library-CAD model based at least in part on the comparison. For example, the comparison may determine that the selected nominal model-interface  854  and/or the nominal model from the library-CAD model conforms to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 , such that the selected nominal model-interface  854  may be aligned with coordinates that correspond to the digital representation of the workpiece-interface  120 , and/or the selected nominal model-interface  854  may be substantially congruent with the digital representation of the workpiece-interface  120 . In various exemplary embodiments, step  910  may include selecting the nominal model for a respective workpiece, selecting a three-dimensional portion of the nominal model for a respective workpiece  116  (which may include the nominal model-interface  854 ), and/or selecting only the nominal model-interface  854  for the respective workpiece  116 . 
     When a nominal model or a three-dimensional portion thereof is selected at step  908 , the exemplary method  900  may include determining an extension-segment-CAD model from the library-CAD model. For example, a library-CAD model that includes a nominal extension segment  206  may be determined to sufficiently match a workpiece-interface  120  such that an extension segment  206  may be additively printed on the workpiece-interface  120  without requiring transforming or extending the nominal model-interface  854  at steps  910 ,  912 . On the other hand, when the library-CAD model includes a model of a nominal component  204  or a model of a nominal workpiece  116 , rather than a model of a nominal extension segment  206 , the exemplary method  900  may proceed with generating a model of an extension segment  802  at step  908 , for example, so as to provide a model of an extension segment  802  rather than a model of a component  204  or workpiece  116 . The model of the extension segment  802  generated at step  908  may be configured to be additively printed on the workpiece-interface  120  of the respective one of the plurality of workpieces  116 , whereas a model of a component  204  or workpiece  116  would not be so configured even if the nominal model-interface  854  closely matched the workpiece-interface  120 . 
     In exemplary methods  900  that do not include a matching step  906 , an exemplary method may proceed to generating a model of an extension segment  802  based at least in part on the nominal model-interface  854  at step  908  after having compared the nominal model-interface  854  to the digital representation of the workpiece-interface  120  at step  904 . In some embodiments, steps  904  and  908  may be combined into a single step, such that comparing the nominal model-interface  854  to the digital representation of the workpiece-interface  120  may be part of the process of generating a model of an extension segment  802  based at least in part on the nominal model-interface  854 . 
     After having generated and/or selected a model of an extension segment  802  at steps  908 ,  910 , an exemplary method  900  may ascertain, at step  912 , whether the plurality of workpieces  116  includes another workpiece  116 . When there is another workpiece, the exemplary method  900  may include repeating the determining step  902  and subsequent steps through to step  912 . When step  912  indicates that there are no additional workpieces  116 , the exemplary method  900  may proceed with step  914 , which provides for outputting a model of a plurality of extension segments  802  respectively configured to be additively printed on the corresponding workpiece-interface  120  of the respective ones of the plurality of workpieces  116 . The model may be an extension segment-CAD model  800 , and the model may be based at least in part on the selecting and/or transforming of the nominal model-interface  854  and/or the nominal model from the library-CAD model. 
     The model of the plurality of extension segments  802  may be output at step  914  concurrently as, or subsequently after, each additional workpiece  116  is generated and/or selected at steps  908 ,  910 . In some embodiments, outputting the model may include stitching together a plurality of models, such as models having been respectively selected and/or transformed and generated for respective ones of the plurality of workpieces  116 . While an exemplary method  900  of determining and/or generating an extension segment-CAD model  800  has been described with respect to a plurality of extension segments  206 , it will be appreciated that an extension segment-CAD model  800  may also be determined and/or generated for a single extension segment  206 . For example, the exemplary method  900  may be performed for a single extension segment  206 . 
     Referring now to  FIG. 9B , one or more steps will be described that may be included in the step  908  of generating a model of an extension segment  802  ( FIG. 9A ). The steps shown in  FIG. 9B  may be included individually or together with one or more other steps. When generating a model of an extension segment  802 , one or more steps shown in  FIG. 9B  may be performed, and the particular steps performed may depend at least in part on whether the nominal model-interface  854  provides a partial match or a close match at step  906  ( FIG. 9A ), and/or whether the nominal model-interface  854  or at least a three-dimensional portion of the nominal model are selected at step  910  ( FIG. 9A ). 
     As shown in  FIG. 9B , generating a model of an extension segment  802  at step  908  may include an extracting step  916 , such that an extension segment  206  may be generated based at least in part on a nominal model-interface  854  and/or a three-dimensional portion of a nominal model corresponding to the nominal model-interface  854 . Alternatively, the extracting step  916  may be omitted, for example, such that a nominal model may itself be configured to be additively printed on a workpiece-interface  120 . The step  908  of generating a model of an extension segment  802  may additionally or alternatively include a transforming step  918 , such that a nominal model-interface  854  may be conformed to the digital representation of the workpiece-interface  120 . Alternatively, the transforming step  918  may be omitted, for example, when a nominal model-interface  854  already conforms to the digital representation of the workpiece-interface  120 . The step  908  of generating a model of an extension segment  802  may further additionally or alternatively include an extending step  920 , such that a nominal model-interface  854  or a transformed model-interface  804  may be extended so as to provide a three-dimensional model of an extension segment  802 . Alternatively, the extending step  920  may be omitted, for example, when generating a model of an extension segment  802  from a three-dimensional portion of the nominal model. 
     In some embodiments, at step  916 , generating a model of an extension segment  802  may optionally include extracting from a nominal model based at least in part on the comparison at step  904 ,  906 , a nominal model-interface  854  and/or a three-dimensional portion of the nominal model corresponding to the nominal model-interface  854 . The extracting step may be performed following the comparing step  904 , following the matching step  906 , or following the selecting step  910 . 
     In some embodiments, generating a model of an extension segment  802  may optionally include, at step  918 , transforming a nominal model-interface  854  based at least in part on the comparison at step  904 ,  906 , so as to provide a transformed model-interface  804  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . The transforming step may include one more transforming operations, including aligning, altering, modifying, contorting, distorting, deforming, correcting, adjusting, revising, straightening, tilting, rotating, bending, twisting, or editing, as well as combinations of these. The particular transforming operation(s) may be selected based at least in part on the comparison such that the transforming operation(s) conforms the nominal model-interface  854  to the digital representation of the workpiece-interface  120 . 
     The transforming step  918  may be performed following the comparing step  904  and/or following the matching step  906 . Additionally, or in the alternative, the transforming step  918  may be performed following the extracting step  916 . An exemplary method  900  may include extracting the nominal model-interface  854  from the nominal model and then proceeding to step  918 , providing for transforming the nominal model-interface  854  based at least in part on the comparison at step  904 ,  906 , so as to provide a transformed model-interface  804  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . 
     In some embodiments, generating a model of an extension segment  802  may optionally include, at step  920 , extending the transformed model-interface  804 , such that the extension segment  206  is configured to be additively printed on the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . Step  920  may be performed after having transformed the nominal model-interface  854  at step  918 . Alternatively, in some embodiments, the extending step  920  may be combined with the transforming step  918 . 
     Further additionally, or in the alternative, step  918  may follow step  910  ( FIG. 9A ), providing for extending a nominal model-interface  854  that has been selected at step  910 . For example, when a nominal model-interface  854  closely matches a digital representation of a workpiece-interface  120 , such as may be determined at step  906 , the transforming step  918  may be omitted from the step of generating a model of an extension segment  802  at step  908 . Regardless of whether the nominal model-interface  854  is transformed at step  918  or selected at step  910  with the transforming step  918  being omitted, the extension segment  206  resulting from the extending step  912  may be configured to be additively printed on the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . 
     In an exemplary embodiment, generating a model of an extension segment  802  at step  908  may include, at step  916 , extracting from the nominal model based at least in part on the comparison of the nominal model-interface  854  to a digital representation of workpiece-interface  120 ; at step  918 , transforming the nominal model-interface  854  based at least in part on the comparison so as to provide a transformed model-interface  804  conforming to the digital representation of the workpiece-interface  120 ; and at step  920 , extending the transformed model-interface  804  so as to provide an extension segment  206  configured to be additively printed on the workpiece-interface  120 . 
     Referring still to  FIG. 9B , in another embodiment, the step  908  of generating a model of a nominal extension segment  206  may include, at step  916 , extracting from the nominal model a three-dimensional portion of the nominal model. The three-dimensional portion may correspond to the nominal model-interface  854 . For example, the three-dimensional portion may include the portion of the nominal model above the nominal model-interface  854  and may include the nominal model-interface  854 . The portion of the nominal model below the three-dimensional interface may be deleted from the nominal model and/or may remain unextracted. The three-dimensional portion may have a height corresponding to the height of an extension segment  206  being generated at step  908 . 
     In some embodiments, generating a model of an extension segment  802  may optionally include, at step  922 , transforming a three-dimensional portion of a nominal model corresponding to a nominal model-interface  854  based at least in part on the comparison at step  904 ,  906 , so as to provide a model of an extension segment  802  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . The model of the extension segment  802  so provided may be configured to be additively printed on the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . The three-dimensional portion of the nominal model transformed at step  922  may include a three-dimensional portion extracted at step  916  or at least a three-dimensional portion of a nominal model selected at step  910  ( FIG. 9A ). In some embodiments, the at least a three-dimensional portion of a nominal model selected at step  910  may include the nominal model as a whole, such as when the nominal model is a model of a nominal extension segment  206 . 
     The step  922  of transforming a three-dimensional portion may include transforming the nominal model-interface  854  of the three-dimensional portion, and may include one more transforming operations, including aligning, altering, modifying, contorting, distorting, deforming, correcting, adjusting, revising, straightening, tilting, rotating, bending, twisting, or editing, as well as combinations of these. The particular transforming operation(s) at step  922  may be selected based at least in part on the comparison such that the transforming operation(s) conforms the nominal model-interface  854  to the digital representation of the workpiece-interface  120 . Additionally, or in the alternative, the step  922  of transforming a three-dimensional portion may include extending the nominal model-interface  854  so as to provide an extension segment  206  conforming to the digital representation of the workpiece-interface of the respective one of the plurality of workpieces  116 . 
     Now referring to  FIGS. 10A-10D , exemplary transforming operations  1000  will be described, which may be performed at step  910  in the exemplary method  900  of generating an extension segment-CAD model  800 . Any one or more transforming operations  1000  may be performed so as to conform a nominal model-interface  854  to a digital representation of a workpiece-interface  120 . Such transforming operations  1000  may be performed when transforming the nominal model-interface  854 , for example, as part of a transforming step  910  in an exemplary method  400  of additively printing an extension segment  206  and/or in an exemplary method  90  of determining and/or generating an extension segment-CAD model  800 . 
     The nominal model-interface  854  may differ from a digital representation of a workpiece-interface  120 , for example, because of a change to the shape of a workpiece  116  while in service, or any other difference between workpiece-interface  120  and the library-CAD model from which the nominal model-interface  854  was selected. Additionally, or in the alternative, a nominal model-interface  854  may be selected at a height that differs from the height of the workpiece-interface  120  even though the nominal model corresponds to the component  204 . Such a difference in height may result in a corresponding difference between the nominal model-interface  854  and the workpiece-interface  120 . The transforming operation  1000  may be performed so as to compensate for a difference between the nominal model-interface  854  and the workpiece-interface  120 , regardless of the underlying source for such difference. 
       FIG. 10A  shows an exemplary transforming operation  1000  that includes shifting at least a portion of a nominal model-interface  854  so as to conform the nominal model-interface  854  with a digital representation of a workpiece-interface  120 . As shown in  FIG. 10A , the nominal model-interface  854  is shifted to the right. However, it will be appreciated that a transforming operation  1000  may include shifting a nominal model-interface  854  in any direction, including any direction along a 360-degree axis. 
       FIG. 10B  shows an exemplary transforming operation  1000  that includes rotating at least a portion of a nominal model-interface  854  so as to conform the nominal model-interface  854  with a digital representation of a workpiece-interface  120 . As shown in  FIG. 10B , the nominal model-interface  854  is rotated counterclockwise. However, it will be appreciated that a transforming operation  1000  may include rotating a nominal model-interface  854  in any direction. 
       FIG. 10C  shows an exemplary transforming operation  1000  that includes bending at least a portion of a nominal model-interface  854  so as to conform the nominal model-interface  854  to a digital representation of a workpiece-interface  120 . As shown in  FIG. 10C , by way of example nominal model-interface  854  generally aligns with the workpiece-interface  120  at a middle region, while outward regions are subjected to a bending transforming operation. However, it will be appreciated that a transforming operation  1000  may include bending a portion of a nominal model-interface  854  in any direction. 
       FIG. 10D  shows an exemplary transforming operation  1000  that includes scaling at least a portion of a nominal model-interface  854  so as to conform the nominal model-interface  854  with a digital representation of a workpiece-interface  120 . As shown in  FIG. 10D , by way of example, the nominal model-interface  854  is scaled downward so as to conform to the workpiece-interface  120 . However, it will be appreciated that a transforming operation  1000  may additionally or alternatively include scaling a nominal model-interface  854  upward. 
     Any one or more transforming operations may be carried out alone or in combination with one another, and as to all or a portion of a nominal model-interface  854 . In some embodiments, transforming a nominal model-interface  854 , such as at step  910  of the exemplary method  900 , may include aligning at least a portion of the nominal model-interface  854  with a digital representation of a workpiece-interface  120 . Such aligning may include aligning one or more coordinates of the nominal model-interface  854  with one or more coordinates of the digital representation of the workpiece-interface  120 . By way of example, such aligning may be performed, at least in part, using a shifting, rotating, bending, and/or scaling transforming operation as described with reference to  FIGS. 10A-10D . Additionally, or in the alternative, transforming the nominal model-interface  854  may include a first transforming operation selected to align at least a first portion of the nominal model-interface  854  with a digital representation of a workpiece-interface  120 , such as using a shifting and/or rotating transforming operation as described with reference to  FIGS. 10A and 10B , followed by a second transforming operation selected to align at least a second portion of the nominal model-interface  854  with the digital representation of the workpiece-interface  120  such as using a bending and/or scaling transforming operation as described with reference to  FIGS. 10C and 10D . 
     The first transforming operation may be selected to align a first one or more coordinates of the nominal model-interface  854  with a first one or more coordinates of the digital representation of the workpiece-interface  120 , and the second transforming operation may be selected to align a second one or more coordinates of the nominal model-interface  854  with a second one or more coordinates of the digital representation of the workpiece-interface  120 . 
     The first one or more coordinates of the nominal model-interface  854  may include coordinates for a center point of the nominal model-interface  854  and/or one or more coordinates along the nominal model-interface perimeter  856  of the nominal model-interface  854 , such as a maximum or minimum X coordinate or a maximum or minimum Y coordinate along the nominal model-interface perimeter  856 . The first one or more coordinates of the workpiece-interface  120  may include coordinates for a center point of the workpiece-interface  120  and/or one or more coordinates along the workpiece-interface perimeter  504  of the workpiece-interface  120 , such as a maximum or minimum X coordinate or a maximum or minimum Y coordinate of the workpiece-interface perimeter  504 . The first transforming operation may be configured to align the center point of the nominal model-interface  854  with the center point of the workpiece-interface  120 , and/or to align a maximum or minimum X coordinate or a maximum or minimum Y coordinate along the nominal model-interface perimeter  856  with a corresponding maximum or minimum X or Y coordinate along the workpiece-interface perimeter  504 . 
     The second one or more coordinates of the nominal model-interface  854  may include one or more coordinates along the nominal model-interface perimeter  856  of the nominal model-interface  854 , and the second one or more coordinates of the workpiece-interface  120  may include one or more coordinates along the workpiece-interface perimeter  504 . The second one or more coordinates of the nominal model-interface  854  and/or the second one or more coordinates of the workpiece-interface  120  may be selected based on a comparison of the workpiece-interface  120 . Such comparison may be performed, for example, after the first transforming operation. 
     Coordinates may be selected for the second transforming operation based on a difference between coordinates for a point along the nominal model-interface perimeter  856  as compared to coordinates of a corresponding point along the workpiece-interface perimeter  504 . For example, coordinates for such a point may be selected when the coordinates differ by a threshold amount. The threshold amount may be selected based at least in part on a degree of conformance sufficient to provide a near net shape component  204  when additively printing an extension segment  206  conformed to the workpiece-interface  120  based at least in part on the one or more transforming operations. In this way, once the nominal model-interface  854  has been aligned with the workpiece-interface  120  according to the first transforming operation, one or more second transforming operations may be performed as determined by such comparison relative to such threshold amount. 
     The one or more second transforming operations may be performed to the extent needed to sufficiently conform the nominal model-interface  854  to the workpiece-interface  120  so as to obtain a near net shape component  204 . In some embodiments, a difference may exist between coordinates of one or more points along the nominal model-interface perimeter  856  relative to coordinates of corresponding points along the workpiece-interface perimeter  504 , while still sufficiently conforming the nominal model-interface  854  to the workpiece-interface  120  so as to provide a near net shape component  204 . For example, such difference may be an amount that is at least less than an overhang distance for an overhang  506 . 
     In some embodiments, a transforming operation may provide for an overhang  506  between the workpiece-interface  120  and the model-interface  804 , such that the model-interface  804  overhangs the workpiece-interface  120  by an overhang distance. For example, a transforming operation may include determining an offset amount  604  and transforming at least a portion of a nominal model-interface  854  by the offset amount  604 . The offset amount  604  may correspond to an overhang distance for at least a portion of the extension segment  206 . 
     Now referring to  FIGS. 11A and 11B , and  FIGS. 12A-12D , exemplary methods of extending a model-interface  804  will be described.  FIG. 11A  shows a nominal model, such as from a library-CAD model  850 .  FIG. 11B  shows a model of an extension segment  802 , such as in an extension segment-CAD model  800 , generated based at least in part on the nominal model-interface  854 , such as in steps including extending the nominal model-interface  854 .  FIG. 12  shows a flow chart depicting exemplary methods of extending a model-interface  804  so as to provide a model of the extension segment  802  configured to be additively printed on a workpiece-interface  120  of a respective workpiece  116 . 
     Exemplary methods of extending a model-interface  804  may be performed starting from a nominal or transformed model-interface  804  and/or a three-dimensional portion of a nominal model. As described with reference to  FIGS. 9A and 9B , exemplary methods  900  of generating an extension segment-CAD model  800  may include, at step  920 , extending a selected nominal model-interface  854  or a transformed model-interface  804 . Additionally, the step  922  of transforming a three-dimensional portion may include extending the nominal model-interface  854 . Such a nominal model-interface  854  may have been extracted from the nominal model or may remain part of the nominal model when extending the nominal model-interface  854 . When a nominal model-interface  854  and/or a three-dimensional portion of a nominal model remains part of the nominal model when extending, the resulting extension segment  206  may be extracted from the nominal model, for example, by extracting a three-dimensional portion of a nominal model corresponding to the nominal model-interface  854  as described with reference to step  916 . 
     As shown in  FIG. 11B , a model of an extension segment  802  may include a height, h e , extending from a model-interface  804  to a top surface  808 . The height, h e , for an extension segment  802  may be determined from a nominal model  852 . For example, the height of an extension segment  206 , h e , may correspond to the z-directional distance from a nominal model-interface  854  to a nominal top surface  858  of the nominal model  852 . Alternatively, the height of an extension segment  206 , h e , may be specified independently from the nominal model  852 . An exemplary model of an extension segment  802  may be extended from the model-interface  804  to the nominal top surface  858  of the nominal model  852 . 
     In some embodiments, a model of an extension segment  802  may include a region extending from the model-interface  804  to the top surface  808  of the model. Additionally. or in the alternative, as shown in  FIG. 11B , a model of an extension segment  802  may include a plurality of extension segment slices  1100  between the model-interface  804  to the top surface  808  of the model. The extension segment slices  1100  may correspond to nominal model slices  1102  in the nominal model  852 . The nominal model slices  1102  and/or the extension segment slices  1100  may have any desired z-directional spacing. The nominal model slices  1102  may include a nominal model-interface  854  and/or one or more nominal extended-planes  1104 . The nominal model slices  1102  may correspond to the z-directional resolution of the nominal model, and the extension segment slices  1100  may correspond to the z-directional resolution of the model of the extension segment  802 . In some embodiments, the z-directional resolution of the model of the extension segment  802  may differ from the z-directional resolution of the nominal model  852 . For example, the z-directional resolution of the model of the extension segment  802  may be increased or decreased relative to the z-directional resolution of the nominal model  852 . 
     As shown in  FIG. 12A , an exemplary method  1200  of extending a model-interface  804  may include, at step  1202 , determining a height of a workpiece  116  based at least in part on a digital representation of a field of view  114  that includes at least a portion of the workpiece, at step  1204 , determining a height for an extension segment  206  to be additively printed on a workpiece-interface  120  of the workpiece  116 , and at step  1206 , extending the model-interface  804  in the z-direction by an amount corresponding to the height for the extension segment  206 . The model-interface  804  may be extended in the z-direction within a nominal model and then a resulting model of an extension segment  802  may be extracted therefrom. Alternatively, the model-interface  804  may be extracted from the nominal model, and then the model-interface  804  may be extended in the z-direction by an amount corresponding to the height for the extension segment  206  within a model of the extension segment  802  being generated. 
     Exemplary methods of extending a model-interface  804  at step  1206  are shown in  FIGS. 12B-12D . As shown in  FIG. 12B , extending a model-interface  804  in the z-direction may include, at step  1208 , positioning the model-interface  804  at an elevation corresponding to a build plane  122  of an additive manufacturing machine  104 ; at step  1210 , positioning a copy of the model-interface a distance in the z-direction above the model-interface  804  that corresponds to the height for the extension segment  206 ; and at step  1212 , defining a model of an extension segment  802  extending in the z-direction from the model-interface  804  to the copy of the model-interface  804 . 
     As shown in  FIG. 12C , extending a model-interface  804  in the z-direction may include, at step  1214 , positioning the model-interface  804  at an elevation corresponding to a build plane  122  of an additive manufacturing machine  104 ; at step  1216 , determining a nominal extended-plane  1104  of a nominal model corresponding to a top surface of the nominal model, and positioning the nominal extended-plane  1104  of the nominal model a distance in the z-direction above the model-interface  804  that corresponds to the height for the extension segment  206 ; and at step  1218 , defining a model of an extension segment  802  extending in the z-direction from the model-interface  804  to the nominal extended-plane  1104 . 
     As shown in  FIG. 12D , extending a model-interface  804  in the z-direction may include, at step  1220 , positioning the model-interface  804  at an elevation corresponding to a build plane  122 ; at step  1222 , determining a slice elevation for an extended-plane  1104  of a model of an extension segment  802 ; at step  1224 , determining a nominal extended-plane  1104  in a nominal model, the nominal extended-plane  1104  being at an elevation corresponding to the slice elevation for the model of the extension segment  802 ; and at step  1226 , positioning the nominal extended-plane  1104  a distance in the z-direction above the model-interface  804  that corresponds to the slice elevation. 
     In some embodiments, extending a model-interface  804  in the z-direction may include, at step  1228 , transforming a nominal extended-plane  1104 , providing a transformed extended-plane  1104 . The transforming of the nominal extended-plane  1104  may be based at least in part on a comparison of the nominal extended-plane  1104  to the model-interface  804 . Additionally, or in the alternative, the transforming of the nominal extended-plane  1104  may be based at least in part on the position of the nominal extended-plane  1104  above the model-interface  804  relative to the height for the extension segment  206 . The transforming at step  1228  may include one more transforming operations, including those shown in  FIGS. 10A-10D , or any other transforming operation, such as aligning, altering, modifying, contorting, distorting, deforming, correcting, adjusting, revising, straightening, tilting, rotating, bending, twisting, or editing, as well as combinations of these. 
     The particular transforming operation(s) at step  1228  may be selected based at least in part on the comparison of the nominal extended-plane  1104  and/or the position of the nominal extended-plane  1104 . In some embodiments, a transforming operation may include a smoothing factor, which may be configured to provide a graduated transition from a model-interface  804  to a transformed extended-plane  1104 . For example, an extended-plane  1104  may have a perimeter that differs from a model-interface perimeter  806 , and the smoothing factor may be configured to provide a gradual transition therebetween. The smoothing factor may temper the transformation by a prorated amount depending on the z-directional location of the extended-plane  1104 . 
     An extended-plane  1104  at a z-direction position that corresponds to the height of the extension segment  206  may not be transformed, such that the model of the extension segment  802  may gradually transition along the z-direction from a model-interface  804  conforming to a workpiece-interface  120  to an extended-plane  1104  conforming to the top surface  858  of the nominal model  852 . Additionally, or in the alternative, an extended-plane  1104  at a z-direction position between the model-interface  804  and the top surface of the extension segment  808  may be transformed with a smoothing factor applied to the transformation, so as to provide a transformed extended-plane  1104  conforming to a perimeter partly between that of the model-interface  804  and that of the top surface of the nominal model  852 . Also, in some embodiments, an extended-plane  1104  at a z-direction position that corresponds to the height of the extension segment  206  may be transformed, for example, to provide top surface  808  of an extension segment  206  that differs from a top surface of the nominal model. 
     Still referring to  FIG. 12D , the step of extending a model-interface  804  in the z-direction may be performed for any number of slices. As shown in  FIG. 12D , an exemplary method  1200  may include, at step  1230 , determining whether the model of the extension segment  802  may include another slice. The number of slices may be predetermined, such as based on the intended height of the model of the extension segment  802  and a z-directional slice interval. A z-directional slice interval may depend on the desired z-directional resolution of the model of the extension segment  802 . When there is another slice, the exemplary method  1200  may include repeating steps  1222  through  1230 . When step  1230  indicates that there are no additional slices, the exemplary method  1200  may proceed with step  1232 , which provides for defining a model of an extension segment  802  extending in the z-direction from the model-interface  804  through each nominal or transformed extended-plane  1104 , with the model extending to the height for the extension segment  206 . The model of the extension segment  802  may be defined at step  1232  concurrently as, or subsequently after, each extension-plane is determined, positioned, and/or transformed at steps  1224 ,  1226 , and  1228 . 
     Referring again to  FIG. 9A , a model of a plurality of extension segments  802  may be output at step  914 , such as to an extension segment-CAD model  800  as shown in  FIG. 8A . Each of the models of the extension segments  802  may include a model-interface  804  aligned in the z-direction to an interface plane in the extension segment-CAD model  800 . The interface plane in the extension segment-CAD model  800  may correspond to a build plane  122  of an additive printing machine  104 . In this way, a plurality of extension segments  206  may be additively printed on workpiece-interfaces  120  of respective workpieces  116  as part of the same build with each extension segment  206  properly aligning in the z-direction with the build plane  122 . Referring again to  FIG. 4 , an exemplary method  400  of additively printing an extension segment  206  includes, at step  408  generating a print command based at least in part on a digital representation of a field of view  114  captured by the vision system.  FIG. 7B , shows an exemplary method  750  of generating a print command for a plurality of slices of one or more extension segments  206 . 
     Now referring to  FIG. 13 , an exemplary print command  1300  for a slice of a plurality of extension segments  206  is graphically depicted. As shown in  FIG. 13 , an exemplary print command  1300  for additively printing a slice of an extension segment  206  may include a plurality of scan paths  1302  respectively corresponding to the slice. In an exemplary embodiment, the print command  1300  may be for a slice that includes a scan path corresponding to the model-interface  804  of the plurality of extension segments  206 . Additional print commands  1300  may be generated for each respective slice as described with reference to  FIG. 7B . The number of slices may depend on the size (e.g., height, thickness) of the extension segment(s)  206  in the extension segment-CAD model  800 , as well as the desired thickness of the layers of powder  126  or other material that may be used to additively print the extension segment(s)  206 . 
     In exemplary embodiments, the extension segment-CAD model  800  may include a model of a plurality of extension segments  802 , in which at least a first model of a first extension segment  802  differs from at least a second model of a second extension segment  802 . The first model of the first extension segment  802  may conform to and may be substantially congruent with a first workpiece-interface  120  of a first workpiece  116 , and the second model of the second extension segment  802  may conform to and be substantially congruent with a second workpiece-interface  120  of a second workpiece  116 . The print command  1300  may include a first scan path corresponding to a first slice of the first extension segment  206  and a second scan path corresponding to a second slice of the second extension segment  206 , and the first scan path may differ from the second scan path. For example, the first scan path may define a first extension segment perimeter and the second scan path may define a second extension segment perimeter, in which the first extension segment perimeter differs from the second extension segment perimeter, such as in respect of curvature, surface area, and/or geometry. 
     Now referring to  FIGS. 14-19 , exemplary pretreatments, methods of determining and/or generating a pretreatment command, and methods of pretreating a workpiece-interface  120  will be further described. 
       FIG. 14  shows an exemplary method  1400  of generating a pretreatment command, which may be performed, for example, as at step  414  in the exemplary method  400  of additively printing an extension segment  206  shown in  FIG. 4 . An exemplary method  1400  may include, at step  1402 , determining and/or generating a pretreatment-CAD model. The pretreatment-CAD model may provide a two-dimensional or a three-dimensional model of the pretreatment region. When the pretreatment-CAD model provides a two-dimensional model of the pretreatment region, the exemplary method  1400  may proceed to step  1404 , providing for determining a pretreatment region and a scan path and for the extension segment-CAD model. When the pretreatment-CAD model provides a three-dimensional model of the pretreatment region, the exemplary method  1400  may proceed with step  1406 , providing for slicing the pretreatment-CAD model, and then step  1404 , providing for determining a pretreatment region and a scan path for each slice of the extension segment-CAD model. After determining a pretreatment region and a scan path for a slice of the extension segment-CAD model at step  1404 , the exemplary method  1400  may proceed with determining, at step  1408 , whether there is another slice, and if so, the exemplary method  1400  may proceed back to step  1404 , providing for determining a pretreatment region and a scan path for a next slice of the pretreatment-CAD model. The exemplary method  1400  may end, at step  1410 , when there are no additional slices for which a pretreatment region and a scan path may be determined. 
     The number of slices in a pretreatment-CAD model may depend on the nature of the pretreatment to be provided. For example, in some embodiments a pretreatment-CAD model for a pretreatment that includes additive-leveling may include more slices than a pretreatment-CAD model for melt-leveling or heat-conditioning. As another example, when a pretreatment includes heat-conditioning or melt-leveling a workpiece-interface without additive-leveling, the pretreatment-CAD model may include only one slice, although such as pretreatment-CAD model may include a plurality of slices. Further, while a pretreatment that includes additive-leveling may utilize a pretreatment-CAD model that includes a plurality of slices, additive-leveling may also be provided using a pretreatment-CAD model that includes only one slice. By way of example, a pretreatment-CAD model may include from 1 to 20 slices, such as from 1 to 10 slices, such as from 1 to 5 slices, such as from 5 to 10 slices, or such as from 10 to 20 slices, depending on the nature of the pretreatment to be provided. In an exemplary embodiment, a pretreatment-CAD model may include from 1 to 5 slices, such as from 1 to 3 slices, or such as from 1 to 2 slices. 
     Now turning to  FIGS. 15A-15R , exemplary pretreatment-CAD models  1500  will be described.  FIGS. 15A, 15D, 15G, 15J, 15M, and 15P  and show exemplary digital representations of an aberrant workpiece-interface  1502  obtained from a field of view  114  of a vision system  102 .  FIGS. 15B, 15E, 15H, 15K, 15N , and  15 Q show exemplary pretreatment-CAD models  1500  respectively corresponding to the digital representations of the aberrant workpiece-interfaces  1502  shown in  FIGS. 15A, 15D, 15G, 15J, 15M, and 15P . The pretreatment-CAD models  1500  may include an additive-leveling pretreatment, a melt-leveling pretreatment, and/or a heat-conditioning pretreatment.  FIGS. 15C, 15F, 15I, 15L, 15O, and 15R  show exemplary pretreated workpiece-interfaces  1504  resulting from pretreating the respective aberrant workpiece-interfaces  120  shown in  FIGS. 15A, 15D, 15G, 15J, 15M, and 15P  according to the corresponding pretreatment-CAD models  1500  shown in  FIGS. 15B, 15E, 15H, 15K, 15N, and 15Q . 
     As shown in  FIGS. 15A, 15D, 15G, and 15J , a workpiece-interface  120  may include one or more congruent region  1506  and one or more aberrant regions  1508 . The one or more congruent regions  1506  may exhibit an absence of aberrant features. Alternatively, as shown in  FIGS. 15M and 15P , an aberrant region  1508  may encompass all or substantially all of a workpiece-interface  120 . When aberrant features are isolated to one or more aberrant regions  1508 , a pretreatment may be performed only on the aberrant regions  1508  of the workpiece-interface  120 . Alternatively, a pretreatment may be performed across all or substantially all of the workpiece-interface  120 . For example, when the aberrant regions  1508  are widespread, it may be desirable to perform a pretreatment across all or substantially all of the workpiece-interface  120  rather than isolating the pretreatment to particular aberrant regions  1508 . Additionally, or in the alternative, it may be desirable to perform a pretreatment across all or substantially all of the workpiece-interface  120 , regardless of whether the aberrant regions  1508  are isolate or widespread, for example, when the pretreatment may enhance the workpiece-interface  120  as a whole such as when the pretreatment may provide a more congruent workpiece-interface  120 , may enhance the workpiece-interface  120  generally, and/or when aberrant features may exist but that are not detectable with the vision system  120  or that have not been detected with the vision system. 
     The absence of aberrant features in the one or more congruent regions  1506  may be directly determined from a digital representation of the workpiece-interface  120  obtained from a vision system  102 , or the absence of aberrant features may be inferentially determined, for example, when aberrant features have not been directly determined in a region or regions of the digital representation of the workpiece-interface  120 . The one or more aberrant regions  1508  may exhibit one or more aberrant features. The presence of aberrant features in the one or more aberrant regions  1508  may be directly determined from the digital representation of the workpiece-interface  120 , or the presence of aberrant features may be inferentially determined, for example, when an absence of aberrant features has not been directly determined from the digital representation of the workpiece-interface  120 . 
       FIG. 15B  shows an exemplary pretreatment-CAD model  1500  determined and/or generated for the aberrant workpiece-interface  1502  shown in  FIG. 15A . As shown, the pretreatment-CAD model  1500  may include a model-interface perimeter  806  having substantial congruency with the workpiece-interface perimeter  504  of the aberrant workpiece-interface  1502 , such that the pretreatment-CAD model  1500  may be configured to apply a pretreatment to all or substantially all of the workpiece-interface  120 . The pretreatment-CAD model  1500  shown in  FIG. 15B  may be selected, for example, even though the aberrant workpiece-interface  1502  shown in  FIG. 15A  may be determined to exhibit aberrant features (e.g., directly determined or inferentially determined) only in one or more aberrant regions  1508 . 
       FIG. 15C  shows a pretreated workpiece-interface  1504  resulting from pretreating the aberrant workpiece-interface  1502  shown in  FIG. 15A  according to the pretreatment-CAD model  1500  shown in  FIG. 15B . As shown, the pretreated workpiece-interface  1504  may include a pretreated surface having substantial congruency with the workpiece-interface perimeter  504 , such that the pretreatment may be applied across all or substantially all of the workpiece-interface  120 . The pretreatment may include remediating aberrant features and/or enhancing one or more features of the workpiece  116  and/or of the workpiece-interface  120  in preparation for additively printing an extension segment on the workpiece-interface  120 . 
       FIG. 15E  shows another exemplary pretreatment-CAD model  1500 . The pretreatment-CAD model  1500  shown in  15 E may be determined and/or generated for the aberrant workpiece-interface  1502  shown in  FIG. 15D . As shown in  FIG. 15E , the pretreatment-CAD model  1500  may include a model-interface perimeter  806  having substantial congruency with a pretreatment region  1510  of the aberrant workpiece-interface  120 . The pretreatment region  1510  may be defined by a pretreatment-region perimeter  1512 . In some embodiments, the pretreatment-CAD model  1500  may be configured to isolate the pretreatment to the aberrant regions  1508  of the workpiece-interface  120 . The pretreatment-CAD model  1500  shown in  FIG. 15E  may be selected, for example, when the aberrant workpiece-interface  1502  shown in  FIG. 15D  may be determined to exhibit aberrant features (e.g., directly determined or inferentially determined) only in one or more aberrant regions  1508 . 
       FIG. 15F  shows a pretreated workpiece-interface  1504  resulting from pretreating the aberrant workpiece-interface  1502  shown in  FIG. 15D  according to the pretreatment-CAD model  1500  shown in  FIG. 15E . As shown, the pretreated workpiece-interface  1504  may include a pretreated surface having substantial congruency with a pretreatment region  1510  defined by a pretreatment-region perimeter  1512 , such that the pretreatment may be isolated to the aberrant regions  1508  of the workpiece-interface  120 . The pretreatment may include remediating aberrant features and/or enhancing one or more features of the workpiece  116  and/or of the workpiece-interface  120  in preparation for additively printing an extension segment on the workpiece-interface  120 . 
     In some embodiments, the pretreatments shown in  FIGS. 15C and 15F  may include additive leveling. For example, the aberrant regions  1508  shown in  FIGS. 15C and 15F  may exhibit skewness and/or a lower elevation relative to the build plane  122  and/or relative to the congruent regions  1506 . In other embodiments, the pretreatment may include melt-leveling. For example,  FIGS. 15G and 15J  show exemplary aberrant workpiece-interfaces  1502  with aberrant regions  1508  that exhibit skewness and/or a higher elevation relative to the build plane  122  and/or relative to the congruent regions  1506 . The aberrant workpiece-interfaces  1502  shown in  FIGS. 15G and 15J  may receive a pretreatment that includes melt-leveling according to pretreatment-CAD models  1500  respectively shown in  FIGS. 15H and 15K . However, it will be appreciated that the pretreatments shown in  FIGS. 15C and 15F  may also include melt-leveling in addition or as an alternative to additive-leveling. Likewise, the pretreatments shown in  FIGS. 15G and 15J  may also include additive-leveling in addition or as an alternative to melt-leveling. 
     The exemplary pretreatment-CAD model  1500  shown in  FIG. 15H  determined and/or generated for the aberrant workpiece-interface  1502  shown in  FIG. 15G , for example, so as to provide a model-interface perimeter  806  having substantial congruency with the workpiece-interface perimeter  504  of the aberrant workpiece-interface  120 . The pretreatment-CAD model  1500  shown in  FIG. 15K  may be determined and/or generated for the aberrant workpiece-interface  1502  shown in  FIG. 15J , for example, to provide a model-interface perimeter  806  having substantial congruency with a pretreatment region  1510  of the aberrant workpiece-interface  120  and thereby isolate the pretreatment to the aberrant regions  1508  of the workpiece-interface  120 . The pretreatment-CAD model  1500  shown in  FIG. 15H  may be selected, for example, even though the aberrant workpiece-interface  1502  shown in  FIG. 15G  may be determined to exhibit aberrant features (e.g., directly determined or inferentially determined) only in one or more aberrant regions  1508 . The pretreatment-CAD model  1500  shown in  FIG. 15K  may be selected, for example, when the aberrant workpiece-interface  1502  shown in  FIG. 15DJ  may be determined to exhibit aberrant features (e.g., directly determined or inferentially determined) only in one or more aberrant regions  1508 . 
       FIG. 15I  shows a pretreated workpiece-interface  1504  resulting from a pretreatment applied to the aberrant workpiece-interface  1502  shown in  FIG. 15G  according to the pretreatment-CAD model  1500  shown in  FIG. 15H . The pretreatment may provide a pretreated workpiece-interface  1504  that includes a pretreated surface having substantial congruency with the workpiece-interface perimeter  504 .  FIG. 15L  shows a pretreated workpiece-interface  1504  resulting from pretreating the aberrant workpiece-interface  1502  shown in  FIG. 15J  according to the pretreatment-CAD model  1500  shown in  FIG. 15E , providing a pretreated surface having substantial congruency with a pretreatment region  1510  defined by a pretreatment-region perimeter  1512  so as to isolate the pretreatment to the aberrant regions  1508  of the workpiece-interface  120 . The pretreatments shown in  FIGS. 15I and/or 15L  may include remediating aberrant features and/or enhancing one or more features of the workpiece  116  and/or of the workpiece-interface  120  in preparation for additively printing an extension segment on the workpiece-interface  120 . 
     While the aberrant workpiece-interfaces  1502  in the embodiments shown in  FIGS. 15A, 15D, 15G, and 15J  include one or more aberrant regions  1508 , in other embodiments, an aberrant workpiece-interface  1502  may include widespread aberrant regions  1508  and/or the aberrant region  1508  may be directly or inferentially determined to encompass all or substantially all of the workpiece-interface perimeter  504 . For example,  FIGS. 15M and 15P  show exemplary embodiments of an aberrant workpiece-interfaces  1502  with the region defined by the workpiece-interface perimeter  504  being the aberrant region  1508 . As shown in  FIGS. 15N and 15Q , a pretreatment-CAD model  1500  may include a model-interface perimeter  806  having substantial congruency with the workpiece-interface perimeter  504  of the respective aberrant workpiece-interface  120 , such that the pretreatment-CAD model  1500  may be configured to apply a pretreatment to all or substantially all of the workpiece-interface  120 .  FIG. 15N  shows a pretreatment-CAD model  1500  configured to provide a pretreatment that includes additive-leveling, and  FIG. 15O  shows a pretreated workpiece-interface  1504  resulting from pretreating the aberrant workpiece-interface  1502  shown in  FIG. 15M  according to the pretreatment-CAD model  1500  shown in  FIG. 15N .  FIG. 15Q  shows a pretreatment-CAD model  1500  configured to provide a pretreatment that includes melt-leveling, and  FIG. 15R  shows a pretreated workpiece-interface  1504  resulting from pretreating the aberrant workpiece-interface  1502  shown in  FIG. 15P  according to the pretreatment-CAD model  1500  shown in  FIG. 15Q . It will be appreciated that the pretreatment shown in  FIG. 15O  may also include a melt-leveling pretreatment and/or a heat-conditioning pretreatment, and that the pretreatment shown in  FIG. 15R  may also include an additive-leveling pretreatment and/or a heat-conditioning pretreatment. 
     Now referring to  FIGS. 16A and 16B , exemplary workpieces  116  having an aberrant workpiece-interface  1502  and corresponding workpieces having a pretreated workpiece-interface  1504  will be discussed.  FIG. 16A  shows an exemplary digital representation of a plurality of workpieces  116  having an aberrant workpiece-interface  1502 . The digital representation may be obtained using the vision system  102 , for example, as described with reference to  FIGS. 6A and 6B . As shown, a scratch coating of powder  126  has been applied to the plurality of workpieces, partially covering some of the aberrant workpiece-interfaces  1502 . In some embodiments, the powder  126  may cover aberrant regions  1508  of the aberrant workpiece-interfaces  1502  that have an elevation below that of the scratch coating. The portions of the aberrant workpiece-interfaces  1502  exposed above the powder may be congruent regions  1506  and/or aberrant regions  1508 . While all of the workpiece-interfaces  120  shown in  FIG. 16A  are identified as aberrant workpiece-interfaces  1502 , sometimes there may be workpiece-interfaces that do not include an aberrant region  1508 . 
     All or a subset of the workpiece-interfaces  120  in a digital representation of a field of view  114  may be pretreated according to a pretreatment-CAD model. The pretreatment-CAD model may include a plurality of models corresponding to respective ones of the plurality of workpiece-interfaces  120 . The respective models within the pretreatment-CAD model may differ as between respective workpiece-interfaces  120 , for example, so as to apply a customized pretreatment to respective ones of the workpiece-interfaces  120 . Alternatively, a pretreatment-CAD model may include a plurality of models differing only in respect of their coordinates, so as to apply a common pretreatment as between respective ones of the plurality of workpiece-interfaces  120 . However, even when the models in a pretreatment-CAD differ only in respect of their coordinates, a pretreatment resulting from such a pretreatment-CAD model may differ as between respective ones of the workpiece-interfaces  120 . For example, with a scratch coating of powder  126  applied as shown in  FIG. 16A , a pretreatment-CAD model may apply an additive-leveling pretreatment to portions of the aberrant workpiece-interface  1502  (e.g., congruent regions  1606  or aberrant regions  1508 ) covered by the scratch coating of powder  126 , while portions of the aberrant workpiece-interface  1502  protruding above the scratch coating of powder  126  (e.g., congruent regions  1506  or aberrant regions  1508 ) may receive a melt-leveling pretreatment. 
     In some embodiments, the pretreatment-CAD model need not distinguish between the portions of the aberrant workpiece-interface  1502  that are to receive an additive-leveling pretreatment and the portions of the workpiece-interface  1502  that are to receive a melt-leveling pretreatment. Instead, those portions of the aberrant workpiece-interface  1502  covered by the scratch coating of powder  126  may receive an additive-leveling pretreatment while those portions of the aberrant workpiece-interface  1502  protruding from the scratch coating of powder  126  may receive a melt-leveling pretreatment, regardless of where transitions may exist between portions covered by the scratch coating and portions protruding from the scratch coating. Alternatively, in some embodiments an additive-leveling pretreatment may be applied specifically to the aberrant regions  1508  covered by the scratch coating and/or a melt-leveling pretreatment may be applied specifically to the aberrant regions  1508  protruding from the scratch coating. 
       FIG. 16B  shows an exemplary digital representation of a plurality of workpieces  116  after having a pretreatment applied thereto such that the workpieces have a pretreated workpiece-interface  1504 . The pretreated workpiece-interfaces  1504  shown in  FIG. 16B  may reflect a pretreatment applied to the aberrant workpiece-interfaces  1502  shown in  FIG. 16A . As shown, the pretreated workpiece-interfaces  1504  may have a congruent region  1506  substantially congruent with the workpiece-interface perimeter  504 . For example, the pretreated workpiece-interfaces  1504  may be substantially level with a scratch coating of powder  126  as a result of an additive-leveling and/or melt-leveling pretreatment. 
     Now turning to  FIG. 17 , an enlarged view of an exemplary pretreated workpiece-interface  1504  is shown. The pretreated workpiece-interface may include contour lines  1700  resulting from the scan path of the energy source  142 . The contour lines  1700  may reflect additive-leveling, melt-leveling, and/or heat-conditioning, reflecting one or more aberrant features having been remediated and/or one or more features of the workpiece-interface  120  having been enhanced. For example, the contour lines  1700  may enhance bonding between the workpiece  116  and an extension segment  206  additively printed on the workpiece-interface  120  following pretreatment. 
     Now turning to  FIGS. 18A and 18B , exemplary methods of determining and/or generating a pretreatment-CAD model will be described. As shown in  FIG. 18A , an exemplary method  1850  of generating a pretreatment-CAD model may be performed for each of a plurality of workpieces  116 . An exemplary method  1850  may include, at step  1852 , determining in a library-CAD model, a nominal model-interface  854  traversing a nominal model corresponding to a respective one of the plurality of workpieces  116 . The nominal model may include a model of a nominal component  204 , such as a model of a component  204  from which the workpieces  116  may have originated. The workpieces  116  may, however, differ from a component  204  having been additively manufactured according to the nominal model, for example, because of damage or wear incurred by the workpieces  116  as a result of the environment with which the component  204  was used, and/or from a subtractive modification performed to prepare the workpiece  116  for an extension segment  206  to be additively printed thereon. The nominal model may additionally or alternatively include a model of a nominal workpiece, such as a nominal model of a workpiece  116  produced by subjecting a nominal component  204  to a subtractive modification process to provide a workpiece-interface  120 . The nominal model may additionally or alternatively include a model of a nominal pretreatment region  1510 , such as a nominal model of a pretreatment region  1510  corresponding to a nominal workpiece  116 . 
     Determining a nominal model-interface  854  may include determining a plane traversing the library-CAD model at a determined height. The determined height may correspond to a height of an expected location of a workpiece-interface  120  for a nominal workpiece  116 . By way of example, a library-CAD model may include a model of a nominal component  204  corresponding to the workpiece  116 , and the workpiece  116  may have been subjected to a subtractive modification, such as to provide a workpiece-interface  120 . An expected location of a workpiece-interface  120  may be determined based at least in part on the nature of the subtractive modification, such as based on an expected amount of material removed or a resulting change in height of the workpiece  116  as a result of the subtractive modification. 
     Additionally, or in the alternative, the determined height may correspond to a height of a workpiece-interface  120  as determined from a digital representation of the workpiece  116 . The height of a workpiece-interface  120  may be measured based at least in part on one or more dimensions of the workpiece  116  obtained from the digital representation of the workpiece, and a nominal model-interface  854  may be determined based at least in part on the measured height. Additionally, or in the alternative, the height of the workpiece-interface  120  may be measured based at least in part one or more dimensions of a workpiece alignment system  200  captured in a field of view  114 . For example, a height of the workpiece-interface  120  may be determined based at least in part on the height of a workpiece shoe  214 , or based at least in part on a difference between the height of the workpiece-interface  120  and the height of a workpiece shoe  214 , or based at least in part on a difference between the height of the workpiece-interface  120  and the height of the build plate  118 . 
     In some embodiments, a nominal model-interface  854  may be determined using a best-fit algorithm. Determining the nominal model-interface  854  traversing the library-CAD model  850  may include determining a plane traversing the library-CAD model that meets a metric associated with a best-fit algorithm applied with respect to the digital representation of the workpiece-interface  120 . The best-fit algorithm may compare one or more planes traversing the library-CAD model to the digital representation of the workpiece-interface  120  until a compared plane satisfies the best-fit metric. The nominal model-interface  854  may be determined based at least in part on a plane that satisfies the best-fit metric. For example, a plane that satisfies the best-fit metric may be determined to be the nominal model-interface  854 . 
     Still referring to  FIG. 18A , an exemplary method  1850  of determining and/or generating a pretreatment-CAD model may include, at step  1854 , comparing the nominal model-interface  854  of the library-CAD model to a digital representation of the workpiece-interface  120  of the respective ones of the plurality of workpieces  116 . The digital representation may have been previously or concurrently obtained using a vision system  102  that has a field of view  114  including the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . The comparison may be performed using an image matching algorithm. In some embodiments, comparing the nominal model-interface  854  to the digital representation of the workpiece-interface  120  may include, at step  1856 , determining whether the nominal model-interface  854  and the digital representation of the workpiece-interface  120  sufficiently match one another. However, in some embodiments a matching step  1856  need not be included. 
     When included, a matching step  1856  may include comparing one or more coordinates of the nominal model-interface  854  with one or more coordinates of the digital representation of the workpiece-interface  120  and determining one or more differences therebetween. The comparing step  1854  may additionally or alternatively include comparing one or more coordinates of the one or more registration points  202  with a corresponding one or more coordinates of the nominal model-interface  854  of the library-CAD model and determining one or more differences therebetween. The registration points  202  may correspond to locations of respective ones of a plurality of workpieces  116  onto which respective ones of a plurality of extension segments  206  are to be additively printed using the additive manufacturing machine  104 . The comparing step  1854  and the matching step  1856  may be performed separately or together as part of the same step. In some embodiments, the matching step  1856  may determine whether there is a partial match, a close match, or no match between the nominal model-interface  854  and the workpiece-interface  120 . Alternatively, the matching step  1856  may determine whether there is any match (e.g., at least a partial match), or no match between the nominal model-interface  854  and the workpiece-interface  120 . 
     When the matching step  1856  determines that there is at least a partial match between the nominal model-interface  854  and the workpiece-interface  120 , the exemplary method  1850  may proceed to step  1858 , providing for generating a model of a pretreatment region  1510  based at least in part on the nominal model-interface  854 , with the model of the pretreatment region  1510  configured to expose the workpiece-interface  120  of the respective one of the plurality of workpieces  116  to a pretreatment. 
     When the matching step  1856  determines that there is not at least a partial match between the nominal model-interface  854  and the workpiece-interface  120 , the exemplary method  1850  may return to step  1852  so as to determine a different nominal model-interface  854  and to compare the different nominal model-interface  854  to the digital representation of the workpiece-interface  120 . The different nominal model-interface  854  may be selected form the same library-CAD model or a different library-CAD model. 
     In some embodiments, the matching step  1856  may include determining whether there is more than a partial match, such as a close match between the nominal model-interface  854  and the workpiece-interface  120 . When the matching step  1856  determines that there is a close match between the nominal model-interface  854  and the workpiece-interface  120 , the exemplary method  1850  may include, at step  1860 , selecting the nominal model-interface  854  and/or at least a three-dimensional portion of the nominal model from the library-CAD model based at least in part on the comparison. For example, the comparison may determine that the selected nominal model-interface  854  and/or the nominal model from the library-CAD model conforms to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 , such that the selected nominal model-interface  854  may be aligned with coordinates that correspond to the digital representation of the workpiece-interface  120 , and/or the selected nominal model-interface  854  may be substantially congruent with the digital representation of the workpiece-interface  120 . In various exemplary embodiments, step  1860  may include selecting the nominal model as a whole for a respective workpiece, selecting a three-dimensional portion of the nominal model for a respective workpiece  116  (which may include the nominal model-interface  854 ), and/or selecting only the nominal model-interface  854  for the respective workpiece  116 . 
     When a nominal model or a three-dimensional portion thereof is selected at step  1858 , the exemplary method  1850  may include determining a pretreatment-CAD model from the library-CAD model. For example, a library-CAD model that includes a nominal pretreatment region  1510  may be determined to sufficiently match a workpiece-interface  120  such that a workpiece  116  may be subjected to a pretreatment that conforms to the workpiece-interface  120  without requiring transforming or extending the nominal model-interface  854  at steps  1860 ,  1862 . In other embodiments, the exemplary method  1850  may proceed with generating a model of a pretreatment region  1510  at step  1858 , for example, based at least in part on a library-CAD model that includes a model of a nominal component  204 , a model of a nominal workpiece  116 , or a model of a nominal extension segment  206 . The model of the pretreatment region  1510  generated at step  1858  may be configured to expose a workpiece-interface  120  of a respective one of the plurality of workpieces  116  to a pretreatment. 
     In exemplary methods  1850  that do not include a matching step  1856 , an exemplary method may proceed to generating a model of a pretreatment region  1510  based at least in part on the nominal model-interface  854  at step  1858  after having compared the nominal model-interface  854  to the digital representation of the workpiece-interface  120  at step  1854 . In some embodiments, steps  1854  and  1858  may be combined into a single step, such that comparing the nominal model-interface  854  to the digital representation of the workpiece-interface  120  may be part of the process of generating a model of a pretreatment region  1510  based at least in part on the nominal model-interface  854 . 
     After having generated and/or selected a model of a pretreatment region  1510  at steps  1858 ,  1860 , an exemplary method  1850  may ascertain, at step  1862 , whether the plurality of workpieces  116  includes another workpiece  116 . When there is another workpiece, the exemplary method  1850  may include repeating the determining step  1852  and subsequent steps through to step  1862 . When step  1862  indicates that there are no additional workpieces  116 , the exemplary method  1850  may proceed with step  1864 , which provides for outputting a model of a plurality of pretreatment regions  1510  respectively correspond to the workpiece-interfaces  120  of the respective ones of the plurality of workpieces  116 . The model may be a pretreatment-CAD model, and the model may be based at least in part on the selecting and/or transforming of the nominal model-interface  854  and/or the nominal model from the library-CAD model. 
     The model of the plurality of pretreatment regions  1510  may be output at step  1864  concurrently as, or subsequently after, each additional pretreatment region  1510  is generated and/or selected at steps  1858 ,  1860 . In some embodiments, outputting the model may include stitching together a plurality of models, such as models having been respectively selected and/or transformed and generated for respective ones of the plurality of workpieces  116 . While an exemplary method  1850  of determining and/or generating a pretreatment-CAD model has been described with respect to a plurality of pretreatment regions  1510 , it will be appreciated that a pretreatment-CAD model may also be determined and/or generated for a single pretreatment region  1510 . For example, the exemplary method  1850  may be performed for a single workpiece  116 . 
     Referring now to  FIG. 18B , exemplary embodiments of generating a model of a pretreatment region  1510  at step  1858  ( FIG. 18A ) will be further described. When generating a model of a pretreatment region  1510 , one or more steps shown in  FIG. 18B  may be performed, and the particular steps performed may depend at least in part on whether the nominal model-interface  854  provides a partial match or a close match at step  1856  ( FIG. 18A ), and/or whether the nominal model-interface  854  or at least a three-dimensional portion of the nominal model are selected at step  186 A) ( FIG. 18A ). 
     As shown in  FIG. 18B , generating a model of a pretreatment region  1510  at step  1858  may include an extracting step  1866 , such that a pretreatment region  1510  may be generated based at least in part on a nominal model-interface  854  and/or a three-dimensional portion of a nominal model corresponding to the nominal model-interface  854 . Alternatively, the extracting step  1866  may be omitted, for example, such that a nominal model may itself be configured to subject a workpiece-interface  120  to a pretreatment. The step  1858  of generating a model of a pretreatment region  1510  may additionally or alternatively include a transforming step  1868 , such that a nominal model-interface  854  may be conformed to the digital representation of the workpiece-interface  120 . Alternatively, the transforming step  1868  may be omitted, for example, when a nominal model-interface  854  already conforms to the digital representation of the workpiece-interface  120 . The step  1858  of generating a model of a pretreatment region  1510  may further additionally or alternatively include an extending step  1870 , such that a nominal model-interface  854  or a transformed model-interface  804  may be extended so as to provide a three-dimensional pretreatment region  1510 . Alternatively, the extending step  1870  may be omitted, for example, when generating a three-dimensional model of a pretreatment region  1510  from a three-dimensional portion of the nominal model. 
     In some embodiments, at step  1866 , generating a model of a pretreatment region  1510  may optionally include extracting from a nominal model based at least in part on the comparison at step  1854 ,  1856 , a nominal model-interface  854  and/or a three-dimensional portion of the nominal model corresponding to the nominal model-interface  854 . The extracting step may be performed following the comparing step  1854 , following the matching step  1856 , or following the selecting step  1860 . 
     In some embodiments, generating a model of a pretreatment region  1510  may optionally include, at step  1868 , transforming a nominal model-interface  854  based at least in part on the comparison at step  1854 ,  1856 , so as to provide a transformed model-interface  804  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . The transforming step may include one more transforming operations, including aligning, altering, modifying, contorting, distorting, deforming, correcting, adjusting, revising, straightening, tilting, rotating, bending, twisting, or editing, as well as combinations of these. The particular transforming operation(s) may be selected based at least in part on the comparison such that the transforming operation(s) conforms the nominal model-interface  854  to the digital representation of the workpiece-interface  120 . 
     The transforming step  1868  may be performed following the comparing step  1854  and/or following the matching step  1856 . Additionally, or in the alternative, the transforming step  1868  may be performed following the extracting step  1866 . An exemplary method  1850  may include extracting the nominal model-interface  854  from the nominal model and then proceeding to step  1868 , providing for transforming the nominal model-interface  854  based at least in part on the comparison at step  1854 ,  1856 , so as to provide a transformed model-interface  804  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . 
     In some embodiments, generating a model of a pretreatment region  1510  may optionally include, at step  1870 , extending the transformed model-interface  804 , so as to provide a three-dimensional pretreatment region  1510 . Step  1870  may be performed after having transformed the nominal model-interface  854  at step  1868 . Alternatively, in some embodiments, the extending step  1870  may be combined with the transforming step  1868 . 
     Further additionally, or in the alternative, step  1868  may follow step  1860  ( FIG. 18A ), providing for extending a nominal model-interface  854  that has been selected at step  1860 . For example, when a nominal model-interface  854  closely matches a digital representation of a workpiece-interface  120 , such as may be determined at step  1856 , the transforming step  1868  may be omitted from the step of generating a model of a pretreatment region  1510  at step  1858 . Regardless of whether the nominal model-interface  854  is transformed at step  1868  or selected at step  1860  with the transforming step  1868  being omitted, the extension segment  206  resulting from the extending step  1862  may be configured to be additively printed on the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . 
     In an exemplary embodiment, generating a model of a pretreatment region  1510  at step  1858  may include, at step  1866 , extracting from the nominal model based at least in part on the comparison of the nominal model-interface  854  to a digital representation of workpiece-interface  120 ; at step  1868 , transforming the nominal model-interface  854  based at least in part on the comparison so as to provide a transformed model-interface  804  conforming to the digital representation of the workpiece-interface  120 ; and at step  1870 , extending the transformed model-interface  804  so as to provide a model of a pretreatment region  1510  that conforms to the workpiece-interface  120  of a workpiece  116 . 
     Referring still to  FIG. 18B , in another embodiment, the step  1858  of generating a model of a pretreatment region  1510  may include, at step  1866 , extracting from the nominal model a three-dimensional portion of the nominal model. The three-dimensional portion may correspond to the nominal model-interface  854 . For example, the three-dimensional portion may include a portion of the nominal model above and/or below the nominal model-interface  854  and may include the nominal model-interface  854 . The three-dimensional portion of the nominal model below the nominal-model interface  854  may correspond to at least a portion of the workpiece-interface  120  to be subjected to additive leveling. The three-dimensional portion of the nominal model above the nominal-model interface  854  may correspond to a pretreatment layer of powder  126  applied to the workpiece-interface in connection with the pretreatment. 
     In some embodiments, generating a model of a pretreatment region  1510  may optionally include, at step  1872 , transforming a three-dimensional portion of a nominal model corresponding to a nominal model-interface  854  based at least in part on the comparison at step  1854 ,  1856 , so as to provide a model of a pretreatment region  1510  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . The model of the pretreatment region  1510  may be configured to expose the workpiece-interface  120  of the respective one of the plurality of workpieces  116  to a pretreatment. The three-dimensional portion of the nominal model transformed at step  1872  may include a three-dimensional portion extracted at step  1866  or at least a three-dimensional portion of a nominal model selected at step  1860  ( FIG. 18A ). In some embodiments, the at least a three-dimensional portion of a nominal model selected at step  1860  may include the nominal model as a whole, such as when the nominal model is a model of a nominal pretreatment region  1510 . 
     The step  1872  of transforming a three-dimensional portion may include transforming the nominal model-interface  854  of the three-dimensional portion, and may include one more transforming operations, including aligning, altering, modifying, contorting, distorting, deforming, correcting, adjusting, revising, straightening, tilting, rotating, bending, twisting, or editing, as well as combinations of these. The particular transforming operation(s) at step  1872  may be selected based at least in part on the comparison such that the transforming operation(s) conforms the nominal model-interface  854  to the digital representation of the workpiece-interface  120 . Additionally, or in the alternative, the step  1872  of transforming a three-dimensional portion may include extending the nominal model-interface  854  so as to provide a pretreatment region  1510  conforming to the digital representation of the workpiece-interface  120  of the respective one of the plurality of workpieces  116 . 
     Now referring to  FIG. 19 , an exemplary pretreatment command  1900  for pretreating a plurality of aberrant workpiece-interfaces  1502  is graphically depicted. As shown in  FIG. 19 , a pretreatment command  1900  for pretreating a plurality of aberrant workpiece-interfaces  1502  may include a plurality of scan paths  1902  respectively corresponding to the plurality of aberrant workpiece-interfaces  1502 . In an exemplary embodiment, the pretreatment command  1900  includes a scan path corresponding to a model-interface  804  of a plurality of workpiece-interfaces  120  (e.g., a plurality of nominal workpiece-interfaces  120  or a plurality of aberrant workpiece-interfaces  1502 ). Additional pretreatment commands  1900  may be generated for each respective slice of a pretreatment as described with reference to  FIG. 14 . 
     In exemplary embodiments, the pretreatment-CAD model  1500  may include a model of a plurality of pretreatment commands  1900 , in which at least a first model of a first pretreatment region  1510  differs from at least a second model of a second pretreatment region  1510 . The first model of the first pretreatment region  1510  may conform to and may be substantially congruent with a first workpiece-interface  120  (e.g., a first aberrant workpiece-interface  1502 ) of a first workpiece  116 , and the second pretreatment region  1510  may conform to and be substantially congruent with a second workpiece-interface  120  (e.g., a second aberrant workpiece-interface  1502 ) of a second workpiece  116 . The pretreatment command  1900  may include a first scan path corresponding to a first slice of the first pretreatment region  1510  and a second scan path corresponding to a second slice of the second pretreatment region  1510 , and the first scan path may differ from the second scan path. For example, the first scan path may define a first pretreatment region  1510  perimeter and the second scan path may define a second pretreatment perimeter, in which the first pretreatment perimeter differs from the second pretreatment region  1510  perimeter, such as in respect of curvature, surface area, and/or geometry. 
     Now referring to  FIGS. 20-26 , in some embodiments, an exemplary additive manufacturing system  100  may be configured to perform a calibration adjustment so as to prevent or mitigate discrepancies, biases, misalignments, calibration errors, or the like which may otherwise arise from time to time as between one or more aspects of the additive manufacturing system  100 . For example, a calibration adjustment may be configured to prevent or mitigate discrepancies, biases, misalignments, calibration errors, or the like between a vision system  102  and an additive manufacturing machine  104 , between a vision system  102  and one or more CAD models (e.g., extension segment-CAD models and/or pretreatment-CAD models) generated based at least in part on one or more digital images obtained using the vision system  102 , or between one or more CAD models and an additive manufacturing machine  104 , as well as combinations of these. 
     A calibration-CAD model may be utilized to calibrate an additive manufacturing system  100 , such as by performing a calibration adjustment.  FIG. 20  shows an exemplary calibration-CAD model  2000 . The calibration-CAD model  2000  includes one or more model calibration marks  2002 . The one or more model calibration marks  2002  may respectively take the form of or include a model of a registration point  202 . For example, a model calibration mark  2002  may include a dot or other mark that defines a model of a registration point  202 . The one or more model calibration marks  2002  may be respectively located at CAD-model coordinates corresponding respective ones of a plurality of registration points  202  ( FIGS. 2A and 2B ). The registration points  202  may corresponding to locations where respective ones of a plurality of workpieces  116  are to be situated when additively printing on the respective workpiece-interfaces  120  thereof. 
     One or more workpiece docks  210  may be respectively configured to secure a plurality of workpieces  116  to a build plate  118 , and the registration points  202  may provide an indication of where the workpieces  116  are expected to be located when secured to the build plate  118  and installed in the vision system  102  and/or the additive manufacturing machine  104 . A calibration-CAD model  2000  may be utilized by an additive manufacturing machine  104  to additively print model calibration marks  2002  at locations corresponding to the registration points  202 , such as at locations where the workpieces  116  are expected to be located when secured to a build plate  118 . For example, registration points  202  represented by model calibration marks  2002  may correspond to locations of one or more workpiece docks of a build plate  118 . 
     In an exemplary embodiment, respective ones of the plurality of model calibration marks  2002  may have CAD model-coordinates that correspond to respective ones of the plurality of registration points  202 . The model calibration marks  2002  may include a geometric shape or pattern, and at least a portion of the geometric shape or pattern may have CAD model-coordinates that correspond to a respective registration point  202 . In yet another exemplary embodiment, a model calibration mark  2002  may include a contour corresponding to a perimeter of a model of an extension segment  802 , such as a model-interface perimeter  806 , and the contour may have CAD model-coordinates corresponding to a location of a workpiece  116  onto which an extension segment  206  may be additively printed based on the model of the extension segment  802 . 
       FIG. 21  shows an exemplary calibration surface  2100  that includes a plurality of printed calibration marks  2102  that were printed on the calibration surface  2100  using the additive manufacturing machine  104 . The printed calibration marks  2102  may have been printed on the calibration surface  2100  based at least in part on a calibration-CAD model  2000 , such as the calibration-CAD model  2000  shown in  FIG. 20 . The calibration surface  2100  may include a build plate  118 , and/or a calibration sheet applied to a build plate  118 . An exemplary calibration sheet may include transfer paper, carbon paper, or other material suitable for the additive manufacturing machine  104  to print the calibration marks  2102  thereon. In an exemplary embodiment, the printed calibration marks  2102  may be printed using an additive manufacturing tool such as a laser, but without utilizing powder  126  or other additive material. For example, an additive manufacturing machine  104  may include an energy source  142  such as a laser configured to additively print the plurality of extension segments  206  by marking the calibration surface  2100  using the energy source  142 . 
       FIG. 22  shows an exemplary digital representation  2200  of a field of view  114  that includes a plurality of digitally represented calibration marks  2202  having been obtained using a vision system  102 . The digital representation  2200  of the digitally represented calibration marks  2202  in the field of view  114  may be determined using an edge detection algorithm. An exemplary edge detection algorithm may determine the digitally represented calibration marks  2202  by determining pixels within the digital representation  2200  of the field of view  114  that have discontinuities, such as changes in brightness or contrast. As shown in  FIG. 22 , the digital representation  2200  of the field of view  114  may be compared to calibration-CAD model  2000 . For example, respective ones of a plurality of digitally represented calibration marks  2202  may be compared to respective ones of a corresponding plurality of model calibration marks  2002 . 
       FIG. 23  shows an exemplary comparison table  2300  illustrating an exemplary comparison of respective ones of a plurality of digitally represented calibration marks  2202  to corresponding respective ones of a plurality of model calibration marks  2002 . As shown in  FIG. 23 , such a comparison may include determining nominal coordinates  2302  for the model calibration marks  2002  and determining measured coordinates  2304  for the digitally represented calibrations marks  2202 . Such a comparison may additionally include determining a system offset  2306 , such as a difference between respective digitally represented calibrations mark  2202  and corresponding model calibration marks  2002 . Comparison data may be obtained for each model calibration mark  2002 , such as for each corresponding registration point  202 . 
     A system offset  2306  may indicate a discrepancy, bias, misalignment, calibration error, or the like. A calibration adjustment may be performed responsive to the comparison. The calibration adjustment may be applied to any aspect of the additive manufacturing system  100 , including the vision system  102 , the additive manufacturing machine  104 , or a control system  106 . Additionally, or in the alternative, a calibration adjustment may be applied to one or more CAD models, including a library-CAD model and/or an extension segment-CAD model  800 . For example, a calibration adjustment applied to a CAD model may be configured to align coordinates of the CAD model with coordinates of the additive manufacturing system  100 , such as vision system coordinates and/or additive manufacturing machine coordinates. The calibration adjustment may be applied so as to any one or more of the model calibration marks  2002  so as to align each model calibration mark  2002  with a corresponding registration point  202 . For example, a calibration adjustment may be applied as to a model calibration mark  2002  when the system offset  2306  exceeds a threshold offset value. 
     Exemplary results of a calibration adjustment are schematically illustrated in  FIGS. 24A-24C .  FIG. 24A  shows an exemplary digital representation  2400  of a workpiece-interface  120  obtained from a vision system  102  before calibration  2402  and after calibration  2404 , such as for a calibration adjustment applied to the vision system  102 .  FIG. 24B  shows an exemplary location of an extension segment  2410  additively printed using an additive manufacturing machine  104  before calibration  2412  and after calibration  2414 , such as for a calibration adjustment applied to the additive manufacturing machine  104 .  FIG. 24C  shows an exemplary location of a model of an extension segment  2420  in an extension-segment CAD model before calibration  2422  and after calibration  2424 , such as for a calibration adjustment applied to the extension-segment CAD model. 
     Now referring to  FIG. 25 , exemplary methods of calibrating an additive manufacturing system  100  will be described. An exemplary method  2500  may include, at step  2502 , comparing a digital representation of one or more digitally represented calibration marks  2202  to a calibration-CAD model  2000 . The calibration-CAD model  2000  may include one or more model calibration marks  2002 . The digital representation of the one or more digitally represented calibration marks  2202  may have been obtained using a vision system  102 , and the one or more printed calibration marks  2102  may have been printed on a calibration surface  2100  according to the calibration-CAD model  2000  using an additive manufacturing machine  104 . In some embodiments, the exemplary method  2500  may include obtaining the digital representation of the one or more digitally represented calibration marks  2202  using the vision system  102 . 
     One or more calibration adjustments may be applied responsive to step  2502 . For example, in some embodiments, an exemplary method  2500  may include, at step  2504 , applying a calibration adjustment to one or more CAD models based at least in part on the comparison. The calibration adjustment may align the one or more CAD models with one or more coordinates of the additive manufacturing system  100 , such as vision system coordinates and/or additive manufacturing machine coordinates. For example, the calibration adjustment may align the coordinates of one or more model calibration marks  2002  with coordinates of the additive manufacturing machine  104 . Additionally, or in the alternative, an exemplary method  2500  may include, at step  2506 , applying a calibration adjustment to the additive manufacturing system  100  based at least in part on the comparison. The calibration adjustment applied to the additive manufacturing system  100  may be configured to align one or more coordinates of the vision system  102  with one or more coordinates of the additive manufacturing machine  104 . 
     In an exemplary embodiment, a method  2500  of calibrating an additive manufacturing system  100  may include printing one or more model calibration marks  2002  on a calibration surface  2100  according to a calibration-CAD model  2000  using an additive manufacturing machine  104 . The model calibration marks  2002  may be printed on the calibration surface  2100  at a plurality of registration points  202  according to the calibration-CAD model  2000 . The registration points  202  may have CAD-model coordinates respectively corresponding to locations where respective ones of a plurality of workpieces  116  are to be situated when additively printing respective ones of a plurality of extension segments  206  onto the respective ones of the plurality of workpieces  116 . 
     The digital representation of the digitally represented calibration marks  2202  may be compared to the model calibration marks  2002  in the calibration CAD-model  2000  based at least in part on coordinates and/or dimensions of the model calibration marks  2002  and digitally represented calibration marks  2202 . For example, comparing the digital representation of the one or more digitally represented calibration marks  2202  to the model calibration marks  2002  in the calibration-CAD model  2000  may include comparing one or more coordinates of the one or more digitally represented calibration marks  2202  in the digital representation thereof with a corresponding one or more coordinates of the model calibration marks  2002  in the calibration-CAD model  2000 , and determining one or more differences therebetween. The one or more coordinates may include coordinates of respective ones of a plurality of registration points  202  respectively corresponding to locations of respective ones of a plurality of workpieces  116  onto which respective ones of a plurality of extension segments  206  are to be additively printed using the additive manufacturing machine  104 . Additionally, or in the alternative, comparing the digital representation of the one or more digitally represented calibration marks  2202  to the model calibration marks  2002  in the calibration-CAD model  2000  may include comparing one or more dimensions of the one or more digitally represented calibration marks  2202  in the digital representation thereof with a corresponding one or more dimensions of the one or more model calibration marks  2002  in the calibration-CAD model  2000 , and determining one or more differences therebetween. 
     Still referring to  FIG. 25 , the step  2504  of applying a calibration adjustment to one or more CAD models may include transforming at least a portion of the one or more CAD models based at least in part on the comparison at step  2502 . The transforming may include rotating, bending, twisting, shifting, scaling, smoothing, aligning, offsetting, and/or morphing at least a portion of the one or more CAD models. 
     In an exemplary embodiment, the one or more CAD models may include an extension segment-CAD model  800  that has a model of a plurality of extension segments  802  respectively located at CAD model-coordinates corresponding to respective ones of a plurality of registration points  202  respectively corresponding to locations where respective ones of a plurality of workpieces  116  are to be situated when additively printing respective ones of a plurality of extension segments  206  onto the respective ones of the plurality of workpieces  116 . In some embodiments, applying a calibration adjustment to one or more CAD models at step  2504  may include transforming at least a portion of the extension segment-CAD model  800  based at least in part on the comparison so as to align respective ones of the plurality models of extension segments  802  of the extension segment-CAD model  800  with the respective ones of the plurality of registration points  202  of the additive manufacturing system  100 . 
     In still another exemplary embodiment, applying a calibration adjustment to one or more CAD models at step  2504  may include generating an extension segment-CAD model  800 . The generated extension segment-CAD model  800  may include a model of a plurality of extension segments  802  configured to be additively printed onto respective ones of a plurality of workpieces  116 , and the plurality of models of extension segments  802  may be respectively located at CAD model-coordinates determined based at least in part on the calibration adjustment. The plurality of models of extension segments  802  may be aligned with respective ones of a plurality of registration points  202  of the additive manufacturing system  100 . The plurality of registration points  202  may correspond to locations where respective ones of a plurality of workpieces  116  are to be situated when additively printing respective ones of a plurality of extension segments  206  onto the respective ones of the plurality of workpieces  116 . 
     Now referring to  FIG. 26 , further features of an additive manufacturing system  100  will be described. As shown in  FIG. 26 , an exemplary additive manufacturing system  100  may include a control system  106 . An exemplary control system  106  includes a controller  2600  communicatively coupled with a vision system  102  and/or an additive manufacturing machine  104 . The controller  2600  may also be communicatively coupled with a user interface  108  and/or a management system  110 . 
     The controller  2600  may include one or more computing devices  2602 , which may be located locally or remotely relative to the additive vision system  102  and/or the additive manufacturing machine  104 . The one or more computing devices  2602  may include one or more processors  2604  and one or more memory devices  2606 . The one or more processors  2604  may include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, logic device, and/or other suitable processing device. The one or more memory devices  2606  may include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, and/or other memory devices. 
     The one or more memory devices  2606  may store information accessible by the one or more processors  2604 , including machine-executable instructions  2608  that can be executed by the one or more processors  2604 . The instructions  2608  may include any set of instructions which when executed by the one or more processors  2604  cause the one or more processors  2604  to perform operations. In some embodiments, the instructions  2608  may be configured to cause the one or more processors  2604  to perform operations for which the controller  2600  and/or the one or more computing devices  2602  are configured. Such operations may include controlling the vision system  102  and/or the additive manufacturing machine  104 , including, for example, causing the vision system  102  to capture a digital representation of a field of view  114  that includes a workpiece-interface  120  of one or more workpieces  116 , generating one or more print commands  1300  based at least in part on the one or more digital representations of the one or more fields of view  114 , and causing the additive manufacturing machine  104  to additively print respective ones of the plurality of extension segments  206  on corresponding respective ones of the plurality of workpieces  116 . For example, such instructions  2608  may include one or more print commands  1300 , which, when executed by an additive manufacturing machine  104 , cause an additive-manufacturing tool to be oriented with respect to a scan path that includes a plurality of scan path coordinates and to additively print at certain portions of the scan path so as to additively print a layer of the plurality of extension segments  206 . The layer of the plurality of extension segments  206  may correspond to the slice of the extension segment-CAD model  800 . Such operations may additionally or alternatively include calibrating an additive manufacturing system  100 . 
     Such operations may further additionally or alternatively include receiving inputs from the vision system  102 , the additive manufacturing machine  104 , the user interface  108 , and/or the management system  110 . Such operations may additionally or alternatively include controlling the vision system  102  and/or the additive manufacturing machine  104  based at least in part on the inputs. Such operations may be carried out according to control commands provided by a control model  2610 . As examples, exemplary control models  2610  may include one or more control models  2610  configured to determine a workpiece-interface  120  of each of a plurality of workpieces  116  from one or more digital representations of one or more fields of view  114 ; one or more control models  2610  configured to determine and/or generate an extension segment-CAD model  800  based at least in part on the one or more digital representations of the one or more fields of view  114 ; and/or one or more control models  2610  configured to slice an extension segment-CAD model  800  into a plurality of slices and/or to determine or generate a scan path and an additive printing area for each of the plurality of slices. The machine-executable instructions  2608  can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions  2608  can be executed in logically and/or virtually separate threads on processors  2604 . 
     The memory devices  2606  may store data  2612  accessible by the one or more processors  2604 . The data  2612  can include current or real-time data, past data, or a combination thereof. The data  2612  may be stored in a data library  2614 . As examples, the data  2612  may include data associated with or generated by additive manufacturing system  100 , including data  2612  associated with or generated by a controller  2600 , the vision system  102 , the additive manufacturing machine  104 , the user interface  108 , the management system  110 , and/or a computing device  2602 . The data  2612  may also include other data sets, parameters, outputs, information, associated with an additive manufacturing system  100 , such as those associated with the vision system  102 , the additive manufacturing machine  104 , the user interface  108 , and/or the management system  110 . 
     The one or more computing devices  2602  may also include a communication interface  2616 , which may be used for communications with a communications network  2618  via wired or wireless communication lines  2620 . The communication interface  2616  may include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, and/or other suitable components. The communication interface  2616  may allow the computing device  2602  to communicate with the vision system  102 , the additive manufacturing machine  104 . The communication network  2618  may include, for example, a local area network (LAN), a wide area network (WAN), SATCOM network, VHF network, a HF network, a Wi-Fi network, a WiMAX network, a gatelink network, and/or any other suitable communications network for transmitting messages to and/or from the controller  2600  across the communication lines  2620 . The communication lines  2620  of communication network  2618  may include a data bus or a combination of wired and/or wireless communication links. 
     The communication interface  2616  may additionally or alternatively allow the computing device  2602  to communicate with a user interface  108  and/or a management system  110 . The management system  110 , which may include a server  2622  and/or a data warehouse  2624 . As an example, at least a portion of the data  2612  may be stored in the data warehouse  2624 , and the server  2622  may be configured to transmit data  2612  from the data warehouse  2624  to the computing device  2602 , and/or to receive data  2612  from the computing device  2602  and to store the received data  2612  in the data warehouse  2624  for further purposes. The server  2622  and/or the data warehouse  2624  may be implemented as part of a control system  106 . 
     This written description uses exemplary embodiments to describe the presently disclosed subject matter, including the best mode, and also to enable any person skilled in the art to practice such subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the presently disclosed subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.