Patent Publication Number: US-2021170676-A1

Title: Resin adhesion failure detection

Description:
RELATED APPLICATION DATA 
     This application is based on and claims priority under 35 U.S.C. §119 to U.S. Provisional Application No. 62/941,183, filed Nov. 27, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY 
     The present disclosure relates generally to production of components from a slurry, such as a curable resin or ceramic composition, and detection of manufacturing defects in parts manufactured using the slurry. In particular, equipment and methods are disclosed for detecting slurry adhesion and curing when manufacturing a component using an additive manufacturing process, such as when manufacturing a component related to nuclear fission reactors using an additive manufacturing process. 
     BACKGROUND 
     In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention. 
     3D printers provide flexibility to manufacture various components based on computer-inputted designs. However, manufacturing methods using 3D printers suffer from failure-to-adhere delamination caused by a variety of factors. These factors include insufficient curing such as from insufficient UV exposure, lack of supporting structure such as when a volume of cured material does not have a pre-existing portion of the manufactured product on which to adhere, or improper resin formulation which contributes to improper curing or insufficient mechanical properties. Each factor can cause additively manufactured material to fail to adhere to a base component. Such failures can result in a manufactured component that does not meet the product specifications. 
     Inspection of manufactured components can be difficult. For example, detection and validation of an as-manufactured shape directly through imaging is often impractical due to the highly homogenous optical properties of the manufactured material versus those of the constituent materials. In another example, as-manufactured products can have shapes containing complex internal geometry which cannot be easily or accurately detected using ex-situ or post-build measurements, particularly optically-based measurements. 
     In addition, once a manufacturing defect is identified, such as an adhesion failure, there are no known technologies that can remediate such manufacturing defects. 
     SUMMARY 
     Considering the above, it would be advantageous to have equipment and methods to perform quality control during manufacture of resin-based manufactured components. Both detection of resin build quality, such as resin adhesion, and detection of curing defects, such as resin delamination, would improve manufacturing of components. In addition and relevant to additive manufacturing, in-situ measurement and print verification can provide means to perform quality control on complex shapes and structures and, optionally, to remediate such manufacturing defects as adhesion failure. 
     In general, the disclosure is directed to additive manufacturing methods for manufacturing components, particularly components of a nuclear fission reactor structure. In exemplary embodiments, the additive manufacturing method is based on deposition/curing technologies, and these technologies can be used to manufacture objects of almost any shape or geometry using digital model data from, for example, a 3D model or another electronic data source such as a computer-aided design (CAD) model, an Additive Manufacturing File (AMF) file, or a stereolithography contour (SLC) file (usually in sequential layers). Curing of liquid-based materials, e.g., slurries, can use different technologies, each of which solidifies or otherwise forms the liquid-based material in a layer-by-layer approach to build up the manufactured object. Examples include stereolithography (SL) utilizing various optical- or chemical-based curing processes (with associated opto-reactive or chemi-reactive materials). In exemplary embodiments, a method to in-situ monitor production of an additive manufacturing product can be integrated into the additive manufacturing method. The in-situ monitoring method compares images of the slurry during and after manufacturing a layer of the component and compares regions in those images to corresponding images derived from the digital model data for the corresponding layer. The presence or absence of a manufacturing defect, such as an adhesion defect in which material from the slurry volume has not adhered to the deposition surface, a delamination, or a failure to cure, is determined based on this comparison by applying a threshold criteria. Manufacturing defects can include, for example, an adhesion defect in which material from the slurry volume has not sufficiently adhered to the deposition surface. An adhesion defect is typically caused when the material adheres to the surface of the transport film stronger than to the printed part, and breaks off the surface when the part is lifted up. Other manufacturing defects can include, for example, a failure to cure, in which the resin was not cured (did not solidify) due to insufficient exposure or chemical problems, and a delamination, The comparison occurs iteratively on successively manufactured layers of the manufactured component. 
     Embodiments disclosed herein include methods to in-situ monitor production of an additive manufacturing product. 
     In a first embodiment, the method to in-situ monitor production of an additive manufacturing product comprises obtaining a first baseline image of a slurry for additive manufacturing in a first volume of slurry in a build zone of an additive manufacturing machine, forming a layer of the additive manufacturing product via an additive manufacturing process, detecting one or more defects in the layer using a void detection technique, obtaining a second baseline image of the slurry in a second volume of slurry in the build zone of the additive manufacturing machine, detecting one or more defects in the layer using a displacement detection technique, and analyzing an output of the void detection technique and the displacement detection technique to identify a presence or an absence of a manufacturing defect in the additive manufacturing product. In exemplary embodiments, the void detection technique includes, after forming the layer of the additive manufacturing product via an additive manufacturing process, withdrawing the additive manufacturing product from the first volume of slurry to a first withdrawn position, wherein, in the first withdrawn position, the last-formed layer is spaced apart from a plane containing a top surface of the first volume of slurry and spanning the build zone, and capturing a void image of the first volume of slurry in the build zone, wherein, in the void image, the additive manufacturing product is in the first withdrawn position and the first volume of slurry in the build zone is in a post-layer-formation condition that includes one or more voids in the first volume of slurry. In exemplary embodiments, the displacement detection technique includes immersing the additive manufacturing product into the second volume of slurry in the build zone, wherein, in a second immersed position, a surface of the last-formed layer is at a layer depth from the top surface of the second slurry volume, and wherein the layer depth is less than a thickness of the second volume of slurry in the build zone in an as-supplied condition, and capturing a displacement image of the second volume of slurry in the build zone, wherein, in the displacement image, the additive manufacturing product is in the second immersed position and the second volume of slurry in the build zone is in a pre-layer-formation condition that includes, relative to the second volume of slurry in an as-supplied condition, a reduced volume of slurry. 
     In a second embodiment, the method to in-situ monitor production of an additive manufacturing product comprises:
         forming a first portion of the additive manufacturing product in a first deposition step, wherein the additive manufacturing product is attached to a build stage of an additive manufacturing machine;   supplying a first volume of a slurry for additive manufacturing to a build zone of the additive manufacturing machine;   capturing a first image of the first slurry volume in the build zone, wherein, in the first image, the first slurry volume in the build zone is in an as-supplied condition and has a thickness between a top surface oriented toward the build stage of the additive manufacturing machine and a bottom surface oriented toward a curative radiation source of the additive manufacturing machine;   immersing the additive manufacturing product into the first slurry volume in the build zone, wherein, in a first immersed position, the first portion of the additive manufacturing product is at a first layer depth (D Ln ) from the top surface of the first slurry volume, and wherein the first layer depth (D Ln ) is less than the thickness of the first slurry volume in the build zone in the as-supplied condition;   forming a first layer (L a ) on a deposition surface of the first portion from at least a first portion of the first slurry volume located between the deposition surface and the bottom surface of the first slurry volume, wherein a distance between the deposition surface and the bottom surface of the first slurry volume defines a layer thickness (T Ln ) of the first layer (L n );   withdrawing the additive manufacturing product from the first slurry volume, wherein, in a first withdrawn position, the first layer (L n ) is spaced apart from a plane containing the top surface of the first slurry volume and spanning the build zone;   capturing a second image of the first slurry volume in the build zone, wherein, in the second image, the additive manufacturing product is in the first withdrawn position and the first slurry volume in the build zone is in a post-layer-formation condition that includes one or more voids in the first slurry volume;   supplying a second volume of a slurry for additive manufacturing to the build zone of the additive manufacturing machine;   capturing a first image of the second slurry volume in the build zone, wherein, in the second image, the second slurry volume in the build zone is in an as-supplied condition and has a thickness between a top surface oriented toward the build stage of the additive manufacturing machine and a bottom surface oriented toward a curative radiation source of the additive manufacturing machine;   immersing the additive manufacturing product into the second slurry volume in the build zone, wherein, in a second immersed position, a surface of the first layer (L n ) on which a second layer (L n+1 ) will be deposited is at a second layer depth (D Ln+1 ) from the top surface of the second slurry volume, and wherein the second layer depth (D Ln+1 ) is less than the thickness of the second slurry volume in the build zone in the as-supplied condition;   capturing a second image of the second slurry volume in the build zone, wherein, in the second image, the additive manufacturing product is in the second immersed position and the second slurry volume in the build zone is in a pre-layer-formation condition that includes, relative to the second slurry volume in an as-supplied condition, a reduced volume of second slurry;   correcting image properties of the second image of the first slurry volume based on the first image of the first slurry volume to form a corrected void image;   correcting image properties of the second image of the second slurry volume based on the first image of the second slurry volume to form a corrected displacement image; and   comparing (a) the corrected void image to a binary expected image from a computer generated model and (b) the corrected displacement image to the binary expected image from the computer generated model, wherein the binary expected image from the computer generated model is of a layer in the additive manufacturing product corresponding to the first layer (L n ); and   identifying a presence or an absence of a defect in the additive manufacturing product based on the step of comparing       

     The disclosed methods can be embodied as instructions in non-transitory computer-readable storage medium storing instructions for execution by a process. 
     The disclosed methods are applicable to different types of additive manufacturing methods. For example, both the void detection technique and displacement detection technique disclosed herein are applicable to additive manufacturing methods that use a transport system for the slurry. Also for example, the displacement detection technique disclosed herein is applicable to additive manufacturing methods that use a vat-style deposition system for the slurry or that use laser curative radiation, for example, SLA and DLP vat-style deposition systems. 
     The disclosed method allows for in-situ iterative defect detection, which provides efficiencies in manufacturing (time and material) in that, for example, production of a component can be stopped and a part scrapped, if necessary. Additionally, a detected defect in one manufactured layer can be compensated for, corrected or “healed” by adjustment in a subsequent layer&#39;s manufacturing process (and such remediation can be confirmed in-situ before proceeding further with production of the component). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the embodiments, can be better understood when read in conjunction with the appended drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is a schematic, block diagram of an additive manufacturing machine in accordance with some embodiments. 
         FIGS. 2A to 2E  are schematic, block diagrams of various sub-units of the additive manufacturing machine shown in  FIG. 1   
         FIG. 3A  schematically illustrates supplying a slurry to a transporting film of an additive manufacturing machine and  FIG. 3B  is a corresponding example image, as seen from below the transporting film, of a layer of the liquid-based slurry material on the transporting film in an as-supplied condition. 
         FIG. 4A  schematically illustrates translating a build stage of an additive manufacturing machine to an immersion position in which the build stage is immersed into the volume of liquid-based slurry materials and  FIG. 4B  is a corresponding example image, as seen from below the transporting film, of a layer of the liquid-based slurry material on the transporting film with the build stage at the immersion position. 
         FIG. 5A  schematically illustrates translating a build stage of an additive manufacturing machine from the immersion position to a withdrawn position in which the build stage is removed from the volume of liquid-based slurry materials,  FIG. 5B  is a corresponding example image, as seen from below the transporting film, of a layer of the liquid-based slurry material on the transporting film with the build stage at the withdrawn position and showing the voids remaining in the slurry layer, and  FIG. 5C  is a magnified and perspective corrected image corresponding to a portion of the image in  FIG. 5B . 
         FIG. 6  is an image showing a plurality of registry marks located within the field of view of the image capture device. 
         FIG. 7A  schematically illustrates supplying a fresh layer of slurry to a transporting film of an additive manufacturing machine,  FIG. 7B  is a corresponding example image, as seen from below the transporting film, of a layer of the liquid-based slurry material on the transporting film in an as-supplied condition, and  FIG. 7C  is a magnified and perspective corrected image corresponding to a portion of the image in  FIG. 7B . 
         FIG. 8A  schematically illustrates translating a build stage of an additive manufacturing machine from the withdrawn position to an immersion position in which the build stage is immersed into the volume of liquid-based slurry materials,  FIG. 8B  is a corresponding example image, as seen from below the transporting film, of a layer of the liquid-based slurry material on the transporting film with the build stage at the withdrawn position and showing the displacement in the slurry layer, and  FIG. 8C  is a magnified and perspective corrected image corresponding to a portion of the image in  FIG. 8B . 
         FIG. 9  is a schematic cross-sectional side view showing an additive manufacturing product immersed into the slurry volume to the immersed position. 
         FIG. 10A  schematically illustrates a subsequent step in the manufacture of an additive manufacturing product and  FIG. 10B  is a corresponding example image, as seen from below the transporting film, of a layer of the liquid-based slurry material on the transporting film showing the pattern of voids resulting from the most recent additive manufacturing deposition process. 
         FIGS. 11A to 11F  are a flow diagram setting forth steps in an embodiment of a method of manufacturing an additive manufacturing product and to in-situ monitor production of the additive manufacturing product. 
         FIGS. 12A-12C  are example images from different stages of the process of forming a corrected void image. 
         FIGS. 13A-13C  are example images from different stages of the process of forming a corrected displacement image. 
         FIGS. 14A to 14D  are images illustrating aspects of the thresholding process and  FIG. 14E  is an example of a pixel value frequency diagram used in the selection of constants C Lower  and C Higher  during the dynamic thresholding process. 
         FIGS. 15A and 15B  are images illustrating the effects of dynamic thresholding for void images. 
         FIGS. 16A and 16B  are images illustrating the effects of dynamic thresholding for displacement images. 
         FIGS. 17A to 17D  are example images used in the comparison process, including, respectively, a binary void image, a binary displacement image, a binary expected image and a resulting, comparison image. 
         FIG. 18A  is an example collection of comparison images and  FIG. 18B  is an assembled 3D rendering of the comparison images. 
         FIG. 19  is a photograph of an additive manufacturing prototype sample corresponding to the assembled 3D rendering in  FIG. 18B . 
         FIG. 20A  is a magnified, corrected void image showing a plurality of residual slurry within the perimeter of the void and  FIG. 20B  is an image showing an example of a 3D defect model containing true pores. 
         FIG. 21  is a block diagram illustrating an additive manufacturing machine (AMM) controller in accordance with some embodiments. 
     
    
    
     For ease of viewing, in some instances only some of the named features in the figures are labeled with reference numerals. 
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic, block diagram of an additive manufacturing machine  100  in accordance with some embodiments. The additive manufacturing machine  100  includes a number of sub-units (also called “components”) communicably coupled to operate the additive manufacturing machine  100  to manufacture an additive manufacturing product. Sub-units include, among other things, components  102  to supply a source of material to a build zone, components  104  on which the additive manufacturing product is built, components  106  to deposit or cure the material forming successive layers of the additive manufacturing product, components  108  to image the liquid-based materials during deposition of successive layers of the additive manufacturing product, and components  110  to control the additive manufacturing operation based on digital model data and to in-situ monitor the successive layers of the additive manufacturing product for manufacturing defects. Components  110  to control the additive manufacturing operation can be operatively connected to the various sub-units and components by suitable means, such as by digital connections transmitted via wired connections  112  or via wireless connections  114  or via a combination thereof. The various sub-units can be separate components or can be combined or otherwise share components. 
     Details of various sub-units are shown and described with reference to  FIGS. 2A to 2E . 
     For example,  FIG. 2A  schematically illustrates components  102  to supply a source of material to a build zone including a reservoir  200  that contains a supply of liquid-based materials  202 , e.g., a slurry. The reservoir  200  is in fluid communication to an interim reservoir  204 , for example, by tubing  206  having an entrance connected to the reservoir  200  and an exit  208  (directly or indirectly) into the interim reservoir  204 . A valve  210  controls the flow of the liquid-based materials  202  to the interim reservoir  204 . From the interim reservoir  204 , the liquid-based materials  202  are formed into a thin, e.g., less than 100 micron, layer  220  of the liquid-based materials  202  on a transporting film  222  by a metering device  212 , such as a doctor blade. The combination of an adequate volume of liquid-based materials  202  and the structural arrangement of the interim reservoir  204 , the metering device  212  and the transporting film  222  provides an adequate head pressure to form a continuous volume of liquid-based materials  202  in the layer  220  on a first side  224  of the transporting film  222  as the transporting film  222  is translated (t) from the deposition zone  230  into and out from the build zone  240 . Additionally, the layer  220  of the liquid-based materials  202  on the transporting film  222  has, throughout the length (L) and width (W) of the build zone  240 , a thickness (T) relative to the first side  224  of the transporting film  222 , e.g., between a top surface  226  oriented toward the build stage  250 , such as toward a deposition surface  254  of the build stage  250  (see  FIG. 2B ), and a bottom surface  228  oriented toward a curative radiation source  280  such that there is a volume of liquid-based materials  202  in the build zone  240  sufficient to form the to-be-deposited layer of the additive manufacturing product. The thickness (T) may be controlled by the metering device  212 . After passing through the build zone  240 , residual liquid-based materials  202  are collected, for example, to be recirculated to the reservoir  200 . Relative to dimensions consistent with the dimensions of the build zone  240 , the layer  220  of the liquid-based materials  202  is, in the as-supplied condition, continuous and has a substantially consistent thickness (T) as formed by the metering device  212 . 
     The transporting film  222  can be in the form of a continuous belt arranged over rotatable rollers  216 , which rotate (R) to move the transporting film  222  in a first direction (M). The transporting film  222  can be any suitable material that is sufficiently transmissive to the curative radiation so that the curative radiation functions to solidify or otherwise form the liquid-based material into the layers of the manufactured object, is sufficiently chemically inert to the liquid-based materials  202  (at least within the time frame which the liquid-based materials  202  are in contact with the transporting film  222 ) to not influence the composition of the additive manufacturing product, and is sufficiently transparent to allow image capture by the image capture device  300 . In some embodiments, the transporting film  222  can be a film of polyethylene terephthalate, more particularly a film of biaxially-oriented polyethylene terephthalate. 
       FIG. 3A  schematically illustrates an example of a layer  220  of the liquid-based materials  202  on the transporting film  222  in an as-supplied condition and  FIG. 3B  is a corresponding example image of the layer  220  from  FIG. 3A  as seen from below the transporting film  222 , e.g., in the view indicated as A-A′, by the image capture device  300 . As seen in the example image in  FIG. 3B , the layer  220  is in the as-supplied condition and has a uniform appearance, which indicates a uniform thickness (T) and composition. 
     Also for example,  FIG. 2B  schematically illustrates components  104  on which the additive manufacturing product is built including a build stage  250 . The build stage  250  is multi-axial translatable and can be moved in any direction relative to an orthogonally arranged X-axis, Y-axis and Z-axis  252 , where the Z-axis is normal to a plane containing the first side  224  of the transporting film  222 , the X-axis is parallel to the plane containing the first side  224  of the transporting film  222  and is in a direction parallel to the first direction (M) in which the transporting film  222  moves, and the Y-axis is parallel to the plane containing the first side  224  of the transporting film  222  and is in a direction perpendicular to the first direction (M) in which the transporting film  222  moves. The build stage  250  includes a surface on which the additive manufacturing product will be built, e.g., a deposition surface  254 . In some embodiments, the surface  252  is pre-arranged with a base layer of the additive manufacturing product on which subsequent layers will be formed, while in other embodiments, a first layer of the additive manufacturing product is formed directly on the deposition surface  254 . In  FIG. 2B  the deposition surface  254  is a surface of or mounted on the build stage  250 ; in other figures, such as  FIG. 7A , the build stage  250  is depicted with an in-process additive manufacturing product  10 , and the deposition surface  20  is a surface on the in-process additive manufacturing product  10  or, for subsequent layers of the in-process additive manufacturing product  10 , the deposition surface  20  will be the outer surface of the in-process additive manufacturing product  10 , which is regenerated upon each iterative process to be the most distal surface relative to the deposition surface  254  (in the Z-axis). For reference, the length (L) and width (W) of the build zone  240  correspond to the X-axis direction and the Y-axis direction and the thickness (T) of layer  220  of the liquid-based materials  202  on the transporting film  222  corresponds to the Z-axis direction. 
     Typically, the build stage  250  is positioned above the build zone  240  so that the build stage  250  can be translated in the X-axis and Y-axis to a desired position above the volume of liquid-based materials  202  in the build zone  240  and translated in the Z-axis to immerse the deposition surface  254  on which the additive manufacturing product will be built or the deposition surface  20  (depending on the point at which one is in the iterative deposition process) into the volume of liquid-based materials  202  in the build zone  240 . As shown in  FIG. 3A , the build stage  250  (and in particular, the deposition surface  254 ) is aligned with the curative radiation source  280  along an axis  256 . 
     As an example and as shown in  FIG. 4A , in a first translation of the build stage  250  in the Z-axis, the deposition surface  254  (if in an initial deposition layer) or a previously deposited layer of an in-process additive manufacturing product  10  (if in a subsequent or in-process deposition layer) can be immersed into the volume of liquid-based materials  202  in the build zone  240 . The volume of liquid-based materials  202  in the build zone  240  is in the as-supplied condition consistent with the thickness (T) of the layer  220  of the liquid-based materials  202  as formed by the metering device  212 . Immersing the deposition surface  254  (or in-process additive manufacturing product  10 ) locates the deposition surface at a layer depth (D L ) (relative to a top surface  226  of the layer  220  of the liquid-based materials  202  in an as-supplied condition). The layer depth (D L ) is less than the thickness (T) of the layer  220  of the liquid-based materials  202  in the build zone  240  in an as-supplied condition. The difference between the layer depth (D L ) and the thickness (T) of the layer  220  corresponds to the maximum thickness (T L ) of the to-be-deposited layer of the additive manufacturing product (T L =T−D L ). 
       FIG. 4B  is a corresponding image of the layer  220  from  FIG. 4A  as seen from below the transporting film  222 , e.g., in the view indicated as B-B′, by the image capture device  300 . As seen in the example image in  FIG. 4B , in the region A of the layer  220  in which the deposition surface  254  (or in-process additive manufacturing product  10 ) has been immersed, a portion of the volume of the liquid-based materials  202  in the build zone  240  has been displaced. The displacement results in a reduced thickness of the liquid-based materials  202  in areas of the layer  220  that correspond to the geometry and other structural features of the deposition surface. This displacement is observable (as seen from below the transporting film  222 ) as a change in appearance in the layer  220  relative to the appearance of the layer  220  in the as-supplied condition (as an example compare  FIG. 4B  with the image of the as-supplied condition in  FIG. 3B ). In the example image in  FIG. 4B , the layer  220  in the region B (outside of region A) is substantially undisturbed and in the as-supplied condition, while the layer  220  in the region A has a change in appearance reflecting the displacement resulting from the immersion of the deposition surface  254 . 
     Also for example, in a second translation of the build stage  250  in the Z-axis and after any deposition process to form an as-deposited layer on the deposition surface (whether on deposition surface  254  or on a subsequent or in-process deposition layer of in-process additive manufacturing product  10 ), the just deposited, in-process additive manufacturing product  10  is withdrawn from the volume of liquid-based materials  202  in the build zone  240 . Typically, the second translation of the build stage  250  in the Z-axis is to a withdrawn position in which the deposition surface  20  of the just-formed layer, e.g., a first layer (L n ) or any subsequent layer (L n+1 ), is spaced apart from the plane containing the top surface  226  of the layer  220  and that spans the build zone  240 . By being spaced apart, when the transporting film  222  moves in a first direction (M) to transport a new portion of the layer  220  of the liquid-based materials  202  into the build zone  240 , the deposition surface  20  of the just-formed layer will not contact a top surface  226  of the layer  220  of the liquid-based materials  202  and will not disturb the as-supplied condition of the layer  220 . 
     Also schematically illustrated in  FIG. 2B , the build stage  250  can include or be operatively connected to a wireless transceiver  258 . Although shown in connection with build stage  250 , any one or more of the components of additive manufacturing machine  100  can include or be operatively connected via wireless transceivers. 
       FIG. 5A  schematically illustrates an example of an in-process additive manufacturing product  10  in the withdrawn position and after having been formed while immersed into the volume of liquid-based materials  202  in the build zone  240  and before the transporting film  222  has moved in the first direction (M) to transport a new portion of the layer  220  of the liquid-based materials  202  into the build zone  240 , and  FIG. 5B  is a corresponding image of the layer  220  from  FIG. 5A  as seen from below the transporting film  222 , e.g., in the view indicated as C-C′, by the image capture device  300 .  FIG. 5C  is a magnified and perspective corrected example of the region P 1  in the image in  FIG. 5B . In the example images, the layer  220  of the liquid-based materials  202  includes one or more voids  290 , that are formed by the liquid-based materials  202  having been formed into the as-deposited layer of the in-process additive manufacturing product  10 . The voids represent the negative space remaining in the layer  220  of the liquid-based material  202  after a portion of the liquid-based material  202  has been manufactured into the as-deposited layer of the in-process additive manufacturing product  10 . Furthermore, the pattern  292  of voids  290  is representative of the deposition surface  20  of the just-formed, as-deposited layer on the deposition surface  20  and the in-process additive manufacturing product  10  has been withdrawn from the volume of liquid-based materials  202 , e.g., to a withdrawn position. Such voids  290  are artifacts of the deposition process and correspond in geometry and other structural features to the just-formed as-deposited layer. In addition to pattern  292  in region P 1  in the images in  FIGS. 5A and 5B , the image contains a second pattern  292 ′ of voids. This second pattern  292 ′ is due to the image being taken after a prior deposition process. An image taken after a first deposition process would not have a second pattern  292 ′. 
     The process of the first translation of the build stage  250 , formation of the first as-deposited layer, the second translation of the build stage  250 , and then moving the transporting film  222  to transport a new portion of the layer  220  of the liquid-based materials  202  into the build zone  240  can be iteratively repeated to form multiple as-deposited layers (L 1 , L 2 , . . . L n−1 , L n ), where n equals the number of as-deposited layers forming the additive manufacturing product. 
     Returning to the sub-units of the additive manufacturing machine  100 ,  FIG. 2C  schematically illustrates components  106  to deposit or cure the material forming successive layers of the additive manufacturing product including a curative radiation source  280 . As seen in various figures, the curative radiation source  280  is positioned to project curative radiation  282  through the transporting film  222  and into the layer  220  of the liquid-based materials  202 , e.g., the slurry for additive manufacturing, that is located in the build zone  240 . Any suitable curative radiation source  280  can be used that can cure (or otherwise solidify) the liquid-based materials  202 . In exemplary embodiments, the curative radiation source  280  uses electromagnetic radiation at a specified wavelength that reacts with opto-reactive materials in the liquid-based materials  202 . Stereolithography (SL), digital light processing (DLP), and electron-beam-based techniques can be used. 
       FIG. 2D  schematically illustrates components  108  to image the liquid-based materials during deposition of successive layers of the additive manufacturing product, which include an image capture device  300  and an illumination source  310 . The image capture device  300  is positioned with a field of view along axis  302  that includes the build zone  240  viewed through the transporting film  222  so as to be capable of capturing images of the liquid-based materials  202  during deposition of successive layers of the additive manufacturing product. Such images can include, for example, images of (i) the layer  220  of liquid-based materials  202  in the as-supplied condition, e.g., see  FIGS. 3B and 7B , (ii) the layer  220  of liquid-based materials  202  when the in-process additive manufacturing product  10  is in the withdrawn position and after having been immersed into the volume of liquid-based materials  202  in the build zone  240  and before the transporting film  222  has moved in the first direction (M) to transport a new portion of the layer  220  of the liquid-based materials  202  into the build zone  240 , e.g., see  FIG. 5B , and (iii) the layer  220  of liquid-based materials  202  when the in-process additive manufacturing product  10  is immersed into the volume of liquid-based materials  202  in the build zone  240  and the deposition surface  20  on the just-deposited, prior layer (L n−1 ) of the in-process additive manufacturing product  10  is located at the layer depth (D L ), e.g., see  FIG. 8B . The axis  302  of the field of view of the image capture device  300  may be at an angle (α) to the axis  256  associated with the curative radiation emanating from the curative radiation source  280 . The value of the angle (α) is used in image processing and analysis of the various acquired images. Optionally, the image capture device  300  can be in-line with the curative radiation source  280 . An example image capture device  300  includes a high resolution camera using CCD, CMOS or hyperspectral imaging technology, and having a resolution of  4  megapixel or more and  16  megapixel or less. Although described herein as images, the images can be either still images or video and include digital formats. 
     The illumination source  310  is positioned to project visible light  312  toward the layer  220  of liquid-based materials  202  in the build zone  240 . Typically, the illumination source  310  is on the same side of the build zone  240  as the image capture device  300  so that it provides sufficient light to the build zone  240  to allow for image capture of sufficient quality to allow subsequent image analysis. 
     In some embodiments, one or more, such as a plurality, of registry marks are located within the field of view of the image capture device  300 .  FIG. 6  shows an example of registry marks  330  embodied as a pattern of high contrast dots. The registry marks  330  allow alignment and correspondence between two different collected images. As an example, an example collected image can have each pixel assigned a location relative to a coordinate system established by a first axis  332  and a second axis  334  defined relative to the registry marks  330 . The registry marks  330  also allow triangulation of the image within build window  336  and is used for processing and analysis of the collected images. The registry marks  330  in  FIG. 6  are shown in an example location on stationary targeting strip  338  and relative to the build window  3346  but other locations can be used. In some embodiments, the build window  336  is a window corresponding to the build zone  240 . 
     Returning to the sub-units of the additive manufacturing machine  100 ,  FIG. 2E  schematically illustrates components  110  to control the additive manufacturing operation based on digital model data and to in-situ monitor the successive layers of the additive manufacturing product for manufacturing defects. In example embodiments, the components  110  include a computer or other control device  350  having one or more processing units (processors or cores), (optionally) one or more network or other communications interfaces, memory including a non-transitory computer readable storage medium, and one or more connections including communication buses and/or wireless transceivers  352  for interconnecting components. The connections optionally include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. The controller system includes a user interface having a display device  354  and (optionally) a user interface  356 , such as a keyboard/mouse or other input device. Alternatively, or in addition, the display device  354  can include a touch-sensitive surface, in which case the display device is a touch-sensitive display. 
       FIG. 7A  schematically illustrates a subsequent step in the manufacture of an additive manufacturing product. As an example and as shown in  FIG. 7A , after obtaining the image of the layer  220  of liquid-based materials  202  when the in-process additive manufacturing product  10  is in the withdrawn position as described and illustrated in association with  FIG. 5A-C  and  FIG. 6 , the transporting film  222  can be moved in the first direction (M) to transport a new portion of the layer  220  of the liquid-based materials  202  into the build zone  240 .  FIG. 7A  schematically illustrates an example of a layer  220  of the liquid-based materials  202  on the transporting film  222  in an as-supplied condition and with the build stage  250  in the withdrawn position. Note that this is an in-process representation and that the in-process additive manufacture product  10  is positioned on build stage  250  and is ready for deposition of the next layer on the deposition surface  20 .  FIG. 7B  is a corresponding example image of the layer  220  from  FIG. 7A  as seen from below the transporting film  222 , e.g., in the view indicated as D-D′, by the image capture device  300 . As seen in the example image in  FIG. 7B , the layer  220  is in the as-supplied condition and has a uniform appearance, which indicates a uniform thickness (T) and composition. If depositing the same slurry under the same conditions, then the as-supplied condition for this in-process step should be substantively the same as the as-supplied condition at the beginning of the manufacturing process, e.g., the appearance of the layer  220  in the build zone  240  in the as-supplied condition in the image in  FIG. 7B  should be substantially the same as the appearance of the layer  220  in the build zone  240  in the as-supplied condition in the image in  FIG. 3B  (assuming the imaging parameters are consistent). However, the image in  FIG. 7B  may differ from the image in  FIG. 3B  by having evidence of the most recent deposition process, such as the pattern  292 ″, which has been transported out of the build zone  240  for the next deposition layer.  FIG. 7C  is a magnified and perspective corrected example of the region P 2  in the image in  FIG. 7B  and showing the pattern  292 ″ of voids. 
     In another first translation of the build stage  250  in the Z-axis and as shown in  FIG. 8A , the deposition surface  20  of the previously deposited layer of the in-process additive manufacturing product  10  can be immersed into the volume of liquid-based materials  202  in the build zone  240  when in the as-supplied condition consistent with the thickness (T) of the layer  220  of the liquid-based materials  202  as formed by the metering device  212 . Immersing the deposition surface  20  locates the deposition surface  20  at a layer depth (D L ) (relative to a top surface  226  of the layer  220  of the liquid-based materials  202  in an as-supplied condition). The layer depth (D L ) is less than the thickness (T) of the layer  220  of the liquid-based materials  202  in the build zone  240  in an as-supplied condition. The difference between the layer depth (D L ) and the thickness (T) of the layer  220  corresponds to the maximum thickness (T L ) of the to-be-deposited layer of the additive manufacturing product (T L =T−D L ). 
       FIG. 8B  is a corresponding image of the layer  220  from  FIG. 8A  as seen from below the transporting film  222 , e.g., in the view indicated as E-E′, by the image capture device  300 .  FIG. 8C  is a magnified and perspective corrected example of the region P 3  in the image in  FIG. 8B . As seen in the example images in  FIGS. 8B and 8C , in the region C of the layer  220  in which the deposition surface  20  has been immersed, a portion of the volume of the liquid-based materials  202  in the build zone  240  has been displaced. The displacement results in a reduced thickness of the liquid-based materials  202  in areas of the layer  220  that correspond to the geometry and other structural features of the deposition surface  20 . This displacement is observable (as seen from below the transporting film  222 ) as a change in appearance in the layer  220  relative to the appearance of the layer  220  in the as-supplied condition (as an example compare  FIGS. 8B and 8C  with the images of the as-supplied condition in  FIGS. 7B and 7C ). In the example images in  FIGS. 8B and 8C , the layer  220  in the region D (outside of region C) is substantially undisturbed and in the as-supplied condition. 
     The displacement in region C forms a pattern  370  that is representative of the deposition surface  20 . Thus, the image in  FIGS. 8B and 8C  provides information on the surface of the deposition surface  20  that has just been formed in the prior deposition process and before any subsequent deposition process (for example and more generally, information on a first layer (L n ) prior to deposition of a second layer (L n+1 )). For example, because of the displacive influence of immersing the additive manufacturing product  10  into the slurry volume in the build zone  240  to the immersed position, the portion of the slurry volume between the surface of the first layer (L n ) and the transporting film  222  is thinner than the thickness (T) of the layer  220  in the as-supplied condition. Additionally, this reduced thickness is sufficiently thin that surface features of the surface of the first layer (L n ) can be observed. Observable surface features include the geometric shape of the printed part. The surface features can be observed either directly or indirectly. In direct observation, the slurry is sufficiently transparent that the surface features of the surface of the first layer (L n ) are observable through thickness T L  of the layer  220 . In indirect observation, surface features of the surface of the first layer (L n ) impart characteristics to the slurry that correspond to the surface features. 
     For purposes of illustration and with reference to  FIG. 9 , which is a schematic cross-sectional side-view showing the additive manufacturing product  10  immersed into the slurry volume in the build zone  240  to the immersed position, example surface features are shown including a mesa  400  and a channel  402 , both of which are at a distance (d 1 , d 2  respectively) from a reference surface indicated by dashed line  404  (which can be an imaginary reference surface or, for example, the surface of the last deposited layer of the additive manufacturing product  10 ). Because of the different distances, surfaces of the mesa  400  and of the channel  402  are at different distances relative to the transporting film  222 . Thus, the thickness of the layer  220  slurry between the surfaces of the mesa  400  and of the channel  402  are different. Because of the differences in the surfaces (such as distance (d 1 , d 2 )), the different areas A 1  and A 2  of the slurry have different visual appearances when viewed through the transporting film  222 . These different visual appearances correspond to the underlying surfaces and provide a secondary indicia of the surface features. For example, a surface feature such as a channel  402  (or a hole in the in-process additive manufacturing product  10 ) will result in a thicker slurry between the surface feature and the transporting film  222 , which will be observable as a visibly darker or more opaque portion of the slurry. In contrast, a surface feature such as a mesa  400  will result in a thinner slurry between the surface feature and the transporting film  222 , which will be observable as a visibly lighter or more transparent portion of the slurry. In some embodiments, the thinner slurry between the surface feature and the transporting film is sufficiently transparent that that the actual surface features are observable. 
       FIG. 10A  schematically illustrates a subsequent step in the manufacture of an additive manufacturing product. As an example and as shown in  FIG. 10A , after obtaining the image of the layer  220  of liquid-based materials  202  when the in-process additive manufacturing product  10  is in the immersed position as described and illustrated in association with  FIGS. 9A-C  and after having formed any subsequent layer (L n+1 ) on the deposition surface  20 , the just deposited, in-process additive manufacturing product  10  is withdrawn from the volume of liquid-based materials  202  in the build zone  240 . As previously described in relation to  FIGS. 5A to 5C , typically this second translation of the build stage  250  is in the Z-axis and is to the withdrawn position.  FIG. 10B  is a corresponding image of the layer  220  from  FIG. 10A  as seen from below the transporting film  222 , e.g., in the view indicated as F-F′, by the image capture device  300  and showing the pattern  420  of voids  422  resulting from the most recent additive manufacturing deposition process. 
     The present disclosure also relates to methods to in-situ monitor production of an additive manufacturing product during the additive manufacturing process.  FIGS. 11A to 11F  outline an embodiment of a method  500  to in-situ monitor production of an additive manufacturing process. The various processes outlined in the steps of the flowchart in  FIGS. 11A to 11F  can be read and interpreted in connection with the schematics and images in  FIGS. 3A-B  to  10 A-B. 
     The additive manufacturing process begins by forming or otherwise providing a surface, e.g., a base surface, on which a first layer (L n ) of the additive manufacturing product  10  will be formed. If the first layer (L n ) of the method  500  is an initial layer of the additive manufacturing product  10 , the base surface can be the deposition surface  254  of the build stage  250 ; if the first layer (L n ) of the method  500  is a subsequent layer of the additive manufacturing product  10 , the base surface can be the deposition surface  20  of the just-deposited, prior layer (L n−1 ) of the in-process additive manufacturing product  10 . In the illustrated method  500 , a first portion of the additive manufacturing product  10  is formed in a first deposition step S 505 , wherein the additive manufacturing product is attached to a build stage  250  of an additive manufacturing machine. Forming the first portion can proceed by a process that forms a first layer (L n ) of the additive manufacturing product  10  on the build stage  250  or by a process of forming a subsequent layer (L n+1 ) of the additive manufacturing product  10  onto the deposition surface  20  of the just-deposited prior layer (L n ). 
     Once a first portion of the additive manufacturing product has been formed and the additive manufacturing product is attached to the build stage  250 , the method  500  continues by supplying S 510  a first volume of a slurry for additive manufacturing to a build zone of the additive manufacturing machine.  FIG. 3A  schematically illustrates an additive manufacturing machine during a process of supplying a first volume of a slurry for additive manufacturing to a build zone  240  of the additive manufacturing machine. A volume of liquid-based materials  202 , e.g., slurries, present in an interim reservoir  204  are formed into a thin, e.g., less than 100 micron, layer  220  of the liquid-based materials  202  on a transporting film  222  by a doctor blade  212 , which acts as a metering device  212 . An example thickness of the layer  220  is 30-100 micron, such as 40-80 microns. The transporting film  222  is advanced in a direction (M) and causes the layer  220  of liquid-based materials  202  to also move into the build zone  240  below the build stage  250 , which is the surface on which the additive manufacturing product  10  is formed. 
     After supplying the first volume of a slurry and the layer  220  of the liquid-based materials  202  on a transporting film  222  is in the as-supplied condition (as described herein), the method  500  continues by capturing S 515  an image of the first slurry volume in the build zone  240 .  FIGS. 3A-B  (for an initial layer) schematically illustrate an additive manufacturing machine during a process of capturing an image of the first slurry volume in the build zone  240  and an example image  510  (sometimes referred to herein as a first image of the first slurry volume in the build zone). The first image  510  is captured by the image capturing components  108 , such as image capture device  300  in conjunction with illumination source  310  (as necessary to provide adequate image quality), and is of a first slurry volume in the build zone  240  in an as-supplied condition. The first image  510  of the first slurry volume is taken through the transporting film  222  and shows the bottom surface  228  of the layer  220  of the liquid-based materials  202  that is oriented toward the curative radiation source  280 . In the first image  510 , the slurry volume is substantially undisturbed and uniform. The first image  510  provides baseline information on layer  220  of the liquid-based materials  202  in the as-supplied condition to be used in subsequent calibration and comparison processes. Other factors accounted for by taking sequential, real-time baseline information includes changes in environmental conditions, such as from lighting. For example, the first image  510  in  FIG. 3B  shows lighting effects including a lighting gradient (from light to dark as one goes from left to right in the image as shown by arrow  512 ) and reflections  514  from, for example, the illumination source  310 , or from other equipment  516 . It is also possible to detect non-uniformity in the slurry, such as from streaks resulting from inadequate layer formation or impurities in the liquid-based materials  202  forming the layer  220  of slurry.  FIGS. 7A-C  illustrate this process for a subsequent layer. 
     The method  500  continues and the additive manufacturing product  10  is then immersed S 520  into the first slurry volume in the build zone  240  to a first immersed position and a first layer (L n ) is formed on a deposition surface.  FIGS. 4A-B  schematically illustrates this process (for an initial layer). In the first immersed position, the first portion of the additive manufacturing product  20  (or a first portion of the build stage  250  if the initial deposition of the additive manufacturing product  10 ) is at a first layer depth (D Ln ) from the top surface  226  of the layer  220 , which also forms a first slurry volume in the build zone  240 . The first layer depth (D Ln ) is less than the thickness (T) of the first slurry volume in the build zone  240  in the as-supplied condition and the difference between the first layer depth (D Ln ) and the thickness (T) of the layer  220  corresponds to the maximum thickness (T L ) of the to-be-deposited layer of the additive manufacturing product (T L =T−D Ln ). The first layer (L n ) is formed S 525  on a deposition surface  20  of the first portion from at least a first portion of the first slurry volume located between the deposition surface  20  and the bottom surface of the first slurry volume. The first layer (L n ) is formed on the deposition surface  20  by exposing the first slurry volume to curative radiation  282  from the curative radiation source  280  based on parameters in the 3D model or other electronic data source used to operate the additive manufacturing machine to the make the additive manufacturing product. Exposing connects the newly formed material to the deposition surface to form a continuous body. Additionally, the distance between the deposition surface  20  and the bottom surface of the first slurry volume defines a layer thickness (T Ln ) of the first layer (L n ).  FIGS. 8A-C  illustrate this process for a subsequent layer. 
     After forming the first layer (L n ), the method  500  continues by withdrawing S 530  the additive manufacturing product  10  from the first slurry volume to a withdrawn position.  FIG. 5A  schematically illustrates the additive manufacturing product  10  in the withdrawn position. In the withdrawn position, the just-formed first layer (L n ) is spaced apart from a plane (P) containing the top surface  226  of the first slurry volume and spanning the build zone  240  (for example and as shown in  FIG. 5A , spaced apart from the top surface  226  of the layer  220  by a distance SA). Withdrawing places the just-formed first layer (L n ) in a position where no portion of the just-formed first layer (L n ) will be in contact with the layer  220  of liquid-based materials  202  during subsequent movement of the transporting film  222  in direction (M) to move the just-used portion of the layer  220  of liquid-based materials  202  out of the build zone  240  and to move a new portion of the layer  220  of liquid-based materials  202  (such portion being in the as-supplied condition) into the build zone  240 . 
     Because the volume of material between the deposition surface  20  and the bottom surface  228  of the first slurry volume has formed the first layer (L n ), withdrawing the additive manufacturing product  10  leaves a series of openings or voids in the layer  220  of liquid-based materials  202  corresponding to the withdrawn material formed into the first layer (L n ). The method  500  captures S 535  an image of the slurry in this condition (sometimes referred to herein as a second image of the first slurry volume in the build zone). Example image  530  is of the first slurry volume in the build zone after the first layer (L n ) has been formed, e.g. in the post-layer-formation condition, and the additive manufacturing product  10  has been repositioned to the withdrawn position. The image  530  is captured by the image capturing components  108 , such as image capture device  300  in conjunction with illumination source  310  (as necessary to provide adequate image quality), and is of a first slurry volume in the build zone  240  in post-deposition condition. The image  530  of the first slurry volume is taken through the transporting film  222  and shows the bottom surface  228  of the layer  220  of the liquid-based materials  202  that is oriented toward the curative radiation source  280 . 
     Information on the just-formed first layer (L n ) can be inferred from information in the image  530 . For example, in the post-layer-formation condition, the slurry volume in the build zone includes one or more voids  290 . Because of the correspondence to the withdrawn material formed into the first layer (L n ), these voids  290  can be analyzed and correlated to the build quality of the just-formed first layer (L n ) of the in-process additive manufacturing product  10 . Additionally, if there is residual slurry within the perimeter of the void  290 , such residual slurry may be indicative of manufacturing defects in the just-formed first layer (L n ), such as corresponding to an area in the just-formed first layer (L n ) that is missing material deposited from the slurry and, therefore, has formed a pore in the body of the just-formed first layer (L n ). The presence of pores in the just-formed first layer (L n ) can, over successive deposition processes, lead to porosity in the as-manufactured additive manufacturing product  10 . 
     After capturing image  530 , e.g., after capturing the second image of the first slurry volume in the build zone  240 , the method  500  continues by supplying S 540  a volume of a slurry (sometimes referred to herein as a second volume of slurry) for additive manufacturing to the build zone  240  of the additive manufacturing machine.  FIG. 7A  schematically illustrates an additive manufacturing machine during a process of supplying a second volume of a slurry for additive manufacturing to a build zone  240  of the additive manufacturing machine. A volume of liquid-based materials  202 , e.g., slurries, present in an interim reservoir  204  are formed into a thin, e.g., less than 100 micron, layer  220  of the liquid-based materials  202  on a transporting film  222  by a doctor blade  212 , which acts as a metering device  212 . An example thickness of the layer  220  is 30-100 micron, alternatively 40-80 microns. The transporting film  222  is advanced in a direction (M) and causes a portion of layer  220  of liquid-based materials  202  that is in the as-supplied condition to move into the build zone  240  below the build stage  250 . At the same time, advancement of the transporting film  222  in a direction (M) causes the portion of the layer  220  used in the last deposition process (e.g., the portion with voids  290 ) to move out of the build zone  240 . Eventually, after multiple cycles during which the transporting film  222  is advanced in the direction (M), layer  220  of the liquid-based materials  202  is recovered from the transporting film  222  and collected, for example, for recirculation to the reservoir  200 . 
     After supplying the second volume of slurry for additive manufacturing to the build zone  240 , the method  500  captures S 545  an image of the second volume of slurry in the as-supplied condition (sometimes referred to herein as a first image of the second slurry volume in the build zone). Example image  550  (see  FIG. 7B ) is of the second slurry volume in the build zone in the as-supplied condition. Note that the additive manufacturing product  10  has not yet been in contact with the second slurry volume, and preferably has not been repositioned from the withdrawn position. The image  550  is captured by the image capturing components  108 , such as image capture device  300  in conjunction with illumination source  310  (as necessary to provide adequate image quality). The image  550  of the second slurry volume is taken through the transporting film  222  and shows the bottom surface  228  of the layer  220  of the liquid-based materials  202  that is oriented toward the curative radiation source  280 . In the image  550 , one observes an uniform slurry surface with minimal or no visible variation in material appearance on the “fresh” side of the film. The image  550  provides baseline information on layer  220  of the liquid-based materials  202  in the as-supplied condition to be used in subsequent calibration and comparison processes. 
     The method  500  continues and the additive manufacturing product  10  is immersed S 550  into the second slurry volume in the build zone  240  to a second immersed position.  FIG. 8A  schematically illustrates this process. In the second immersed position, the surface of the first layer (L n ) on which a second layer (L n+1 ) will be deposited is at a second layer depth (D Ln+1 ) from the top surface  226  of the layer  220 , which also forms a second slurry volume in the build zone  240 . The second layer depth (D Ln+1 ) is less than the thickness (T) of the second slurry volume in the build zone  240  in the as-supplied condition and the difference between the second layer depth (D Ln+1 ) and the thickness (T) of the layer  220  corresponds to the maximum thickness (T L2 ) of the to-be-deposited layer of the additive manufacturing product (T L2 =T D Ln−1 ). 
     In some examples, the second immersed position is the same as the first immersed position and the second layer depth (D Ln+1 ) is the same as the first layer depth (D Ln ) (D Ln+1 =D Ln =D L ). This is typically the case when iteratively depositing layers of a first contiguous feature of the additive manufacturing product. However, in other instances, such as when transitioning from a first contiguous feature of the additive manufacturing product to a second contiguous feature, the second layer depth (D Ln+1 ) can vary from the first layer depth (D Ln ). 
     After immersing the additive manufacturing product  10  into the second slurry volume in the build zone  240  to the second immersed position and prior to forming the second layer (L n+1 ) on the deposition surface, the method  500  continues by capturing S555 an image of the second volume of slurry (sometimes referred to herein as a second image of the second slurry volume in the build zone). Example image  570  (see  FIG. 8B ) is of the second slurry volume in the build zone with the additive manufacturing product  10  immersed into the second slurry volume in the build zone  240  to the second immersed position and prior to forming the second layer (L n+1 ) on the deposition surface. The image  570  is captured by the image capturing components  108 , such as image capture device  300  in conjunction with illumination source  310  (as necessary to provide adequate image quality). The image  570  of the second slurry volume is taken through the transporting film  222  and shows the bottom surface  228  of the layer  220  of the liquid-based materials  202  that is oriented toward the curative radiation source  280 . 
     After forming the second layer (L n+1 ), the method  500  continues by withdrawing the additive manufacturing product  10  from the second slurry volume to a withdrawn position (see  FIG. 10A ). 
     Concurrently with or subsequently to capturing the desired images of the layers formed in the additive manufacturing process, the method  500  continues by correcting and then analyzing the captured images. In this process, the correction removes variations in lighting and surface texture from the second (displacement) image and third (void) image by removing details present in the first (baseline) image. For example, image properties of the second image of the first slurry volume (e.g., image  530 ) are corrected S 560  based on the first image of the first slurry volume (e.g., image  510 ) to form a corrected void image. Also, image properties of the second image of the second slurry volume (e.g., image  570 ) are corrected S 565  based on the first image of the second slurry volume (e.g., image  550 ) to form a corrected displacement image. As part of the correction of each image (e.g., images  510 ,  530 ,  550 ,  570 ), the as-obtained image can be corrected for triangulation and offset from the axis normal to the bottom surface  228  of the layer  220  (for example using the registry marks  330  as shown and described in connection with  FIG. 6  and based on angle α), which is also known as “perspective correction.” As applicable, other corrections can be applied to individual images prior to correcting to form the corrected void image and/or corrected displacement image, such as optical lens correction, which accounts for radial distortion induced by the curvature of the lens (such optical lens correction can utilize software, such as using the undistort function in the open-source software OpenCV (available from Open Source Computer Vision Library). 
     Forming the corrected void image proceeds by the following. An example of this process is illustrated by the images in  FIGS. 12A-C . The as-captured image  700  is corrected for perspective and offset to form a first interim corrected image  710 . The first interim corrected image  710  is then corrected for environmental conditions such as (i) reflections on the surfaces in the field of view, such as any glass surfaces and the surface of the transporting film  222 , (ii) variations in coloration of the slurry  202 , and (iii) any lighting gradients. Such correction can occur by normalizing based on the first image of the first slurry volume  530  (e.g., the “start of layer” image). It should be noted that the first image of the first slurry volume may also be corrected for perspective and offset, and the corrected first image of the first slurry volume may then be used as the baseline for correcting the void image for environmental conditions. The result of the corrections is a corrected void image  720 . 
     Forming the corrected displacement image proceeds by the following. An example of this process is illustrated by the images in  FIGS. 13A-C . The as-captured image  730  is corrected for perspective and offset to form a first interim corrected image  740 . The first interim corrected image  740  is then corrected for environmental conditions such as (i) reflections on the surfaces in the field of view, such as any glass surfaces and the surface of the transporting film  222 , (ii) variations in coloration of the slurry  202 , and (iii) any lighting gradients. Such correction can occur by normalizing based on the first image of the second slurry volume  570  (e.g., the “start of layer” image). It should be noted that the first image of the second slurry volume may also be corrected for perspective and offset, and the corrected first image of the second slurry volume may then be used as the baseline for correcting the displacement image for environmental conditions. The result of the corrections is a corrected displacement image  750 . 
     Each layer deposited in an iterative process has at least one corrected void image  720  and at least one corrected displacement image  750 , or alternatively, a plurality of corrected void images  720  and a plurality of corrected displacement images  750 , which form a collection of corrected images associated with the manufacturing of the additive manufacturing product. Typically, one corrected void image  720  is paired with one corrected displacement image  750 . 
     The collection of corrected images are then analyzed using thresholding. The thresholding classifies pixels in each image as either “dark” or “light” based on a threshold level applied on a regional basis based on nearest neighbors. The threshold range is automatically set by determining the mean and standard deviation of the grey-scale or color values of the uncured resin in the image (outside of the build area). The pixels in the build area are then classified as either “uncured resin” or “part” based on their difference from the mean. The “build area” is determined by masking out the bounding box surrounding the printed part geometry. Because this thresholding requires a greater difference from the mean to be classified as “part,” this thresholding is more conservative for void images (as compared to displacement images) because the contrast is higher. 
     Image thresholding is used to classify pixels in the images as either “uncured resin” or “part”. The thresholding process determines whether each pixel&#39;s data value (generally from 0-255) lies in a particular range. In the displacement images, displaced resin appears as either darker or brighter than the uncured resin slurry, which has a very uniform appearance. Similarly, in the void images, the voids appear darker than the uncured resin slurry, which has a uniform appearance. The differences in appearance allows classification by establishing an upper and lower threshold boundary condition on a pixel-by-pixel basis: 
       C Lower &lt;Pixel&lt;C Higher    
     Any pixel values which fall outside the above range, i.e., are less than or equal to C Lower  or are greater than or equal to C Higher , are considered to be “displaced” (for displacement images) or voids (for void images) and thus are resolved as “part”. 
     Because of overlap between color values in color images, there may be some amount of error in the above method. To minimize such error, C Lower  and C Higher  are selected in a way that minimizes total error (as described below). Use of the above general equation provides a statistical method to determine the cured and uncured portions of the slurry on a binary basis, i.e., as either “uncured resin” or “part.” 
     The constants C Lower  and C Higher  are determined algorithmically based on a displacement image. The process for determining the constants C Lower  and C Higher  crops a full displacement image to a reduced area that is determined by the geometry file and ensures that there will not be any image overlap with any previously built layers. For example and with reference to  FIG. 14A to 14D , cropping results in artifacts from prior processes being outside the cropped area C 1 , such as the void artifacts  760  to the left of the image in  FIG. 14A , while retaining the area to be analyzed within the cropped area C 1 , such as the area containing displacement artifacts  770  in the cropped image in  FIG. 14B . Two samples are then taken of the cropped image—a foreground image and a background image, where foreground is the expected printed part and background is uncured, unexposed resin. These two samples are masked out using the expected geometry from the digital model data from, for example, a 3D model or another electronic data source such as a computer-aided design (CAD) model, an Additive Manufacturing File (AMF) file, or a stereolithography contour (SLC) file (usually in sequential layers). These models provide image “slices” defining the layer geometry the printer is commanded to print, which can be converted into a binary image. This image is overlaid onto the captured image to mask out areas which are expected to be printed, and areas which are not. The pixel values from the masked out areas are converted to value frequency diagrams using a binning method.  FIG. 14C  is an example of a masked image and  FIG. 14E  is an example of a pixel value frequency diagram. In the method, the number of pixels from each sample which are equal to a particular value from 0-255 are counted, and then the total counts are divided into the total number of pixels to provide a frequency value. The intersection of the graphed lines for foreground and background frequency determine the upper and lower thresholds for foreground by starting at the peak background value and iterating outwards on each side of the peak background value until the foreground frequency is greater than the background frequency. In the example shown in  FIG. 14E , the upper threshold, i.e, C Higher , is at a pixel value of  168  and the lower threshold, i.e., C Lower , is ata pixel value of 156. Then, image pixel values that fall outside the threshold for “background,” i.e. are less than the lower threshold or greater than the upper threshold, are classified as “foreground.” When analyzing a color image, this process is done for each color channel separately and, in order to be classified as “foreground,” all three color channels must fall outside the lower and upper thresholds for “background.” 
     Continuing the thresholding process, pixels in the image are processed to be white or black and the analyzed image is converted into a binary image (based on black or white pixels) for further classification and use.  FIG. 14D  is an example of such a converted binary image. 
       FIGS. 15A-B  are images illustrating the effects of dynamic thresholding for void images. In particular, a corrected void image  800  is processed by dynamic thresholding resulting in a binary void image  810 .  FIGS. 16A-B  are images illustrating the effects of dynamic thresholding for displacement images. In particular, the corrected displacement image  820  is processed by dynamic thresholding resulting in a binary displacement image  830 . 
     It is additionally noted that the general equations and methods for thresholding can be applied using color-scale in place of gray-scale, in which case the general equations and methods are applied to each of the three color bands (red, green, and blue). 
     The binary void image and binary displacement image for each layer formed in the additive manufacturing process are then compared S 570  to a binary expected image for that layer. The binary expected layer is based on a reference binary image. The reference binary image can be generated based on a CAD model or other input and corresponds to the input used to control the manufacturing of the layer by the additive manufacturing machine. Typically, as an electronic construct, the binary expected image has a higher resolution than any of the images captured by the image capture device  300 . Alternative, the binary expected image can be based on sampling of actual additive manufacturing products.  FIGS. 17A-D  are example images used in the comparison process, including binary void image  850 , binary displacement image  860 , the binary expected image  870  associated with the layer corresponding to the binary void image  850  and the binary displacement image  860 , and the comparison image  880  resulting from the pixel-to-pixel comparison  890 . In the comparison  890 , the binary image from both resin displacement and void detection are compared to the expected geometry at a pixel level. Small connected regions within the manufactured part are compared to provide a regional “confidence level.” 
     One of multiple methods are used to segment the total build area into multiple regions that can be “present” or “not present.” The “confidence level” is the ratio of pixels in a segment that are classified as “part” to the total number of expected pixels. If this ratio is sufficiently high (i.e. at least 50%, but this can change based on material and empirical experience), the entire segment is judged to be present. This method is used particularly when the pixel classifier is tuned to minimize false “part” detections, which will misclassify a fraction of the true “part” pixels as “uncured resin.” Suitable segmentation methods include “by-contour” and “tiled.” The “by-contour” method treats each contiguous region of expected part as a single segment. Because delamination defects have only rarely been observed to occur over partial sections of “contours,” this method is suitable for detecting delamination defects. The tiled method breaks the expected part into square tiles, which enables the detection of partially adhered areas or smaller defects. 
     The default assumption of the comparison is “fail” (or “defect”) unless one or more strong confidence level indicators are above a threshold value, in which case the connected region is considered as successfully adhered. Confidence levels can be implemented based on thresholding or other suitable techniques, such as computer vision methods or neural networks.  
     For example, the binary expected image typically includes one or more contiguous regions. When comparing the corrected void image to the binary expected image from the computer generated model, a percentage of coverage in the corrected void image can be quantified based on a pixel-level comparison within each contiguous region. The presence (or absence) of a manufacturing defect can be indicated based on a percentage of coverage below (or above) a threshold void image value in a portion of the additive manufacturing product corresponding to the contiguous region of the corrected void image. In one embodiment, the threshold void image value is 97% and a percentage of coverage less than 97% correlates to the presence of a manufacturing defect and a percentage of coverage equal to or greater than 97% correlates to the absence of a manufacturing defect. Similarly for comparing the corrected displacement image to the binary expected image from the computer generated model, a percentage of coverage in the corrected void image can be quantified based on a pixel-level comparison within each contiguous region. The presence (or absence) of a manufacturing defect can be identified S555 based on a percentage of coverage below (or above) a threshold displacement image value in a portion of the additive manufacturing product corresponding to the contiguous region of the corrected void image. In one embodiment, the threshold displacement image value is 97% and a percentage of coverage less than 97% correlates to the presence of a manufacturing defect and a percentage of coverage equal to or greater than 97% correlates to the absence of a manufacturing defect. 
     In some embodiments of the method, both the threshold void image value and the threshold displacement image value must be above a threshold to correlate to the absence of a manufacturing defect.  
     In other embodiments, because the void image provides more reliable information related to the condition of the as-manufactured layer, the threshold void image value being above the threshold is sufficient to correlate to the absence of a manufacturing defect, even if the threshold displacement image value is below the threshold. However, on the other hand, in such embodiments, the threshold void image value being below the threshold is sufficient to correlate to the presence of a manufacturing defect, even if the threshold displacement image value is above the threshold. 
     In  FIG. 17D , the regions labeled as F 1  and F 2  represent regions of the layer where the comparison resulted in a fail indication. Such a fail indication corresponds to a lack of deposited material, a failure to cure, a delamination, or some other failure in the additive manufacturing of that location in the layer. A plurality of comparison images can be collected and assembled into a 3D model corresponding to the as-manufactured additive manufacturing product or corresponding to at least a portion of the as-manufactured additive manufacturing product.  FIG. 18A  is an example collection of comparison images  880  (including fail regions F 1  and F 2 ) and  FIG. 18B  is an assembled 3D rendering  900  of the comparison images  880 . In the 3D rendering  900 , the fail regions F 1  and F 2  are visible.  FIG. 19  is a photograph of an additive manufacturing prototype sample corresponding to the assembled 3D rendering  900  in  FIG. 18B  and clearly shows the fail regions F 1  and F 2 . The ability to identify and visualize fail regions, such as F 1  and F 2 , allows for failure detection. The failure detection can be remotely monitored and can be in-situ during the manufacturing process of post-manufacturing, such as when qualifying a manufactured part during quality controls.  
     The disclosed method also provides a method to detect pores within the additive manufacturing product. As previously noted herein, the presence of residual slurry within the perimeter of the void  290  may be indicative of manufacturing defects in the just-formed first layer (L n ). These manufacturing defects can be, for example, a pore in the body of the just-formed first layer (L n ), that leads to porosity in the just-formed first layer (L n ) and, over successive deposition processes, leads to porosity in the as-manufactured additive manufacturing product  10 . To detect residual slurry that has the potential to become a pore, the analysis of a corrected void image can optionally detect residual that can become porous in printed layers. Knowing that pores in print layers cause isolated pockets of slurry to be left on the transporting film  222  within the area defining the void  290 , any slurry detached from and not contiguous with the layer  220  within the perimeter of the void  290  that is not part of the expected geometry of the additive manufacturing product can be assumed to be evidence of a pore. This approach works regardless of the flow of the slurry itself (which may cover varying areas of the contour depending on viscosity) because any isolated drop of slurry cannot have been the result of flow after the deposition event. 
       FIG. 20A  is a magnified, corrected void image  910  and shows a plurality of residual slurry  912  within the perimeter of the void  290 . The residual slurry  912  is detached from and not contiguous with the layer  220 . Image processing identifies residual slurry  912 , typically in the form of drops, with a 30 micron resolution and determines which residual slurry  912  are disconnected from any potential slurry flow In embodiments of the process to classify the “pores”, an image is classified as either “resin” or “void” using the threshold method previously described herein. Then, a “flood fill” algorithm seeded with “resin” is used to classify pixels that are outside of the expected part geometry to remove all connected “resin” classified pixels, including those inside the geometry. Then, all remaining pixels are assumed to be defects as they cannot have been the result of resin flow because they are not connected to the uncured resin. Once identified, residual slurry  912  is categorized as pore sites and the plurality of pore sites for one layer are cataloged. On a layer-by-layer basis, the catalogue of pore sites are compared and any pore sites which persist for more than three layers, alternatively more than one layer, are considered to be true pores. Furthermore, the true pores identified by this process can be incorporated into a 3D defect model.  FIG. 20B  is an image showing an example of a 3D defect model  920  containing true pores  922 . 
     The true pores identified by this process enables quantification of total part density and identification of potential weak points in the as-manufactured part. The high degree of precision of identifying pores by this process has been confirmed by forensic analysis of an as-manufactured part. In particular, a 3D defect model of an as-manufactured part was created and a region of expected high porosity exposed, e.g., by slicing, and examined using a microscope. Pore locations observed using the microscope matched the pore location in the 3D defect model. 
     In some embodiments, the components  110  to control the additive manufacturing operation based on digital model data and to in-situ monitor the successive layers of the additive manufacturing product for manufacturing defects is embodied in a computer system or computer-aided machine, such as a computer controlled additive manufacturing machine. The computer system or computer portion of a computer-aided machine can be a general purpose computer, a special purpose computer, or a server that includes, among other things, non-transitory computer-readable storage medium including instructions for operating and controlling the additive manufacturing machine  100  and an electronic data source, such as a computer-aided design (CAD) model or an Additive Manufacturing File (AMF) file or a stereolithography contour (SLC) file (usually in sequential layers) related to the additive manufacturing product  10 . 
       FIG. 21  is a block diagram illustrating an additive manufacturing machine (AMM) controller  1000  in accordance with some embodiments. The AMM controller  1000  typically includes one or more processing units (processors or cores)  1002 , (optionally) one or more network or other communications interfaces  1004 , memory  1006 , and one or more wired or wireless connections  1008  for interconnecting these components. For example, such connections may include communication buses that optionally includes circuitry (sometimes called a chipset) that interconnects and controls communications between system components. Alternatively, the components may communicate wirelessly using wireless transceivers. The AMM controller system  1000  includes a user interface  1010 . The user interface  1010  may include a display device  1012  and optionally includes an input device  1016 , such as a keyboard/ mouse, a trackpad, and/or input buttons. Alternatively, or in addition, the display device  1012  includes a touch-sensitive surface  1014 , in which case the display device is a touch-sensitive display. The connections  1008  of the AMM controller system  1000  also operatively connects to and interfaces with the various sub-units that are communicably coupled to operate the additive manufacturing machine  100  to manufacture an additive manufacturing product. Thus, the connections  1008  of the controller system  1000  are operatively connected to and interface with components  102  to supply a source of material to a build zone (such as components associated with storing, supplying and transporting the slurry  202 ), components  104  on which the additive manufacturing product is built (such as build stage  250 ), components  106  to deposit or cure the material forming successive layers of the additive manufacturing product (such as curative radiation source  280 ), components  108  to image the liquid-based materials during deposition of successive layers of the additive manufacturing product (such as image capture device  300  and illumination source  310 ). Other components to control the additive manufacturing operation based on digital model data and to in-situ monitor the successive layers of the additive manufacturing product for manufacturing defects can also be included. Additionally, the various sub-units can be separate components or can be combined or otherwise share components. 
     The memory  1006  includes high-speed random-access memory, such as DRAM, SRAM, DDR RAM, or other random-access solid-state memory devices, and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, and/or other non-volatile solid-state storage devices. In some embodiments, the memory  1006  includes one or more storage devices remotely located from the processor(s)  1002 . The memory  1006 , or alternatively the non-volatile memory device(s) within the memory  1006 , includes a non-transitory computer-readable storage medium. In some embodiments, the memory  1006  or the computer-readable storage medium of the memory  1006  stores instructions for executing the method(s) described herein (e.g., by a processor). For example, the memory stores the following programs, modules, and data structures, or a subset or superset thereof:
         an operating system  1020 , which includes procedures for handling various basic system services and for performing hardware dependent tasks;   a network communication module  1022 , which is used for connecting the controller system  1000  to other computers via the one or more connections  1008  (wired or wireless) and one or more network communication interface  1004 ;   an image/video capture module  1024  (e.g., a camera module) for processing an image or video captured by the Imaging Components  108 ;   one or more AMM modules  1030 , including the following modules (or sets of instructions), or a subset or superset thereof:
           a slurry module  1032  for interfacing with and controlling operation of the slurry-related components within the components  102  to supply a source of material to a build zone, including the reservoir  200 , (optionally) the valve  210 , the metering device  212 , and the interim reservoir  204 ;   a transporting film module  1034  for interfacing with and controlling operation of the transporting film-related components within the components  102  to supply a source of material to a build zone, including the transporting film  222  and rotatable rollers  216 ;   a build stage module  1036  for interfacing with and controlling operation of the build stage-related components within the components  104  on which the additive manufacturing product is built, including build stage  250  and wireless transceiver  258 ;   a curative radiation source module  1038  for interfacing with and controlling operation of the curative radiation source-related components within the components  106  to deposit or cure the material forming successive layers of the additive manufacturing product, including curative radiation source  280 ;   an imaging module  1040  for interfacing with and controlling operation of the imaging-related components within the components  108  to image the liquid-based materials during deposition of successive layers of the additive manufacturing product, including image capture device  300  and illumination source  310 ; and   a digital model data module  1042  for interfacing with and controlling operation of components related to the storage, sharing, and accessing of electronic information related to the digital model of the part to be manufactured as well as the digital image information obtained from the image module; and   
           one or more defect detection modules  1060 , including the following modules (or sets of instructions), or a subset or superset thereof:
           an image correction module  1062  and an image comparator module  1064  for, variously, (a) interfacing with image-related components and digital information and (b) controlling operation and application of various image processing functions, including the general equations for classification, perspective correction, and thresholding, and (c) the comparing of images and image-related data and information; and   a product reconstruction module  1066  for interfacing with and controlling components related to the storage, sharing, and accessing of electronic information related to the digital model of the part to be manufactured as well as the digital image information obtained from the image module, and related to the correction and analyses of captured images, as well as the visualization of such information, for example, by computer aided three-dimensional rendering.   
               

     Each of the above identified modules corresponds to a set of executable instructions for performing one or more functions as described above and/or in the methods described in this application (e.g., the additive manufacturing methods, the computer-implemented methods, and other information processing methods described herein). However, these modules (e.g., sets of instructions) need not be implemented as separate software programs, procedures or modules, and thus various subsets of these modules are, optionally, combined or otherwise re-arranged in various embodiments. In some embodiments, the memory  1006  stores a subset of the modules and data structures identified above. In some embodiments, the memory  1006  stores additional modules and data structures not described above. 
     Suitable additive manufacturing equipment can be utilized that can accommodate the specific requirements for the materials to be used in the manufacture of the component (such as chemical resistance), the specific requirements for utilization of the equipment itself (such as specific atmospheric or vacuum requirements), as well as can accommodate the size and geometry of the manufactured component. Examples of suitable additive manufacturing equipment include SLA and DLP machines, electron-beam-based additive manufacturing equipment, and DLP stereolithographic equipment, any one of which can be modified or adapted for specific requirements 
     Example methods of additive manufacturing can comprise providing a design of a component to be manufactured to a controller of an additive manufacturing equipment. Such a design can be incorporated into an additive manufacturing protocol. 
     The additive manufacturing protocol can be developed and/or adapted for use in any suitable additive manufacturing process. Examples of suitable additive manufacturing processes are disclosed in ISO/ASTM52900-15, which defines categories of additive manufacturing processes, including: binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, and photopolymerization. The contents of ISO/ASTM52900-15 are incorporated herein by reference. Sterolithography is a form of additive manufacturing using photopolymerization processes. In example embodiments, stereolithographic additive manufacturing techniques include photoinitiation from exposure to ultraviolet radiation or beta radiation. In some example embodiments, the ultraviolet radiation is generated in a digital light processor (DLP) or in a stereolithography apparatus (SLA). In other example embodiments, the beta radiation is generated in electron-beam (EBeam) equipment or electron irradiation (EBI) equipment. Although the methods and compositions disclosed herein are described within the context of stereolithography, it is expressly contemplated that such methods and compositions can be extended to and or adapted to other additive manufacturing processes. 
     In another aspect of example methods, a supply volume of the slurry composition is established, such as a bath or reservoir. A base portion of a green body of the component is then formed by curing a portion of the slurry composition that is in contact with a movable base of the additive manufacturing equipment. Alternatively, a base portion can be pre-fabricated prior to the initiation of the additive manufacturing process. Additional portions of the green body of the component are formed on a layer-by-layer basis by, first, curing a portion of the slurry composition that is in contact with the base portion to form a first layer of a green body and then, second, curing a portion of the slurry composition that is in contact with the prior deposition layer of the green body to form the additional portions while translating the movable base relative to an interface between a surface of the supply volume and the most recently formed additional portion of the green body. The translation of the movable base is typically in accordance with the design of the component and as directed by the additive manufacturing protocol. In example embodiments, translating the movable base relative to the interface between the surface of the supply volume and the most recently formed additional portion of the green body has an X-axis resolution and a Y-axis resolution of 50 microns or better and has a Z-axis resolution of 20 microns or better. In example embodiments, each additional portion of the green body of the component formed on the layer-by-layer basis has a thickness of at least 25 microns, alternatively 25 microns to 50 microns. Once the layer-by-layer manufacture of the green body of the component is complete, the green body of the component can be removed from the additive manufacturing equipment and sintered (or processed by other debindering/consolidating techniques) to form a densified ceramic. The image capture, image correction, and image comparison process describe herein can be suitable incorporated into this method. 
     Based on one or more of the identified defects and/or other deviations, the additive manufacturing process or slurry compositions can be adjusted to correct, mitigate, or compensate for the defect and/or deviation. For example, constituents of the composition can be adjusted and varied (either the materials chemistry or the amounts of constituents). As another example, one or more parameters of the additive manufacturing technique can be adjusted and varied, such as movement of the build stage (spatially and temporally), temperatures associated with deposition, sequencing of steps, etc. Other process parameters that can be adjusted include parameters such as: increasing the temperature of the reservoir to higher temperatures, reducing viscosity, creating a more uniform layer thickness, adjusting the delay before irradiation to allow for proper leveling of an additive manufacturing print layer, adjusting movement speeds to allow for mitigation of hydraulic bearing forces and print window delamination, providing multiple exposures per layer to limit scattering and increase depth of cure, and continuously varying intensity exposures (movies) to optimize desired properties. Other design parameters that can be adjusted include parameters such as: altering the design for thin geometries that are below the capabilities to be printed, increasing/removing pores which are too small and can become occluded during exposure by scattering, adding drain or cleaning holes to the part to aid in trapped slurry removal, combining gyroid and lattice forms to support delicate geometry with structurally and neutronically useful material. The adjustments in composition and/or parameters can occur independently or in combination. Also, the adjustments in composition and/or parameters can be implemented in subsequent iterations of an in-progress iterative deposition process or in a subsequent iterative deposition process. Alternatively, the adjustment of a composition of the slurry or of a parameter of the additive manufacturing technique can be conducted to determine the effect of varying such composition/parameters. Information on such cause and effect can be developed and used in subsequent iterations of the in-progress iterative deposition process or in a subsequent iterative deposition process. 
     In some manufacturing methods or steps in manufacturing methods, features and structures (or portions thereof) of the additive manufacturing product are manufactured as an integral, unitary structure using, for example, an additive manufacturing process. As used herein, additive manufacturing processes include any technologies that build 3D objects by adding material on a layer-upon-layer basis. In one example, the disclosed methods can be applied for the manufacture of nuclear fission reactor structures and ancillary equipment. An example of a suitable additive manufacturing process utilizes 3-D printing of a metal alloy, such as a molybdenum-containing metal alloy, Zircaloy-4 or Hastelloy X, to form the noted structural features such as the cladding. In other embodiments, a fissionable nuclear fuel composition and/or the thermal transfer agent and/or the moderator materials and/or poisons used as part of the nuclear fission reactor structure can be included within the integral, unitary structure when suitable multi-material, additive manufacturing processes with multiple metals within the feedstock are employed. If the molten metal is not included in the additive manufacturing process, the additive manufacturing process can be paused, a volume of molten metal placed into the fuel cavity (either in liquid or solid form) and the additive manufacturing process continued to complete the structure of the closed chamber. Other alloys that can be used for fission reactor structures and ancillary equipment when employing suitable multi-material, additive manufacturing processes with multiple metals within the feedstock include: steel alloys, zirconium alloys, and molybdenum-tungsten alloys (for the cladding and/or for the containment structure); beryllium alloys (for the reflector); and stainless steel (for the containment structure). Even when not manufactured by an additive manufacturing process, the above materials can be used in manufacturing the various features and structures of such fission reactors and ancillary equipment. 
     Additive manufacturing techniques disclosed herein can include the additional steps of: (a) predictive and causal analytics, (b) in-situ monitoring combined with machine vision and accelerated processing during the layer-by-layer fabrication of the structure, (c) automated analysis combined with a machine learning component, and (d) virtual inspection of a digital representation of the as-built structure. In addition, additive manufacturing technology can create complex geometries and, when coupled with in-situ sensors, machine vision imagery, and artificial intelligence, allows for tuning of the manufacturing quality as the components are built on a layer-by-layer additive basis (often, these layers are on the scale of 50 microns) and provides predictive quality assurance for the manufacture of such reactors and structures. 
     Various materials can be used for additively manufacturing components of nuclear fission reactors and ancillary equipment For cladding, typically a corrosion-resistant material with low absorption cross section for thermal neutrons is used. Example materials include Zircaloy or steel, although other materials may be used if suitable to the reactor conditions, such as metallic and ceramic systems (Be, C, Mg, Zr, O, and Si), as well as compositions including molybdenum, tungsten, rhenium, tantalum, hafnium and alloys thereof, including carbides. For fissionable nuclear fuel, the composition can be high-assay low-enriched uranium (HALEU) which has a U 235  assay above 5 percent but below 20 percent or can be highly enriched uranium (HEU) with uranium that is 20% or more U 235 . A suitable fissionable nuclear fuel composition applicable to the disclosed fuel element structure includes uranium oxide (UO 2 ) that is less than 20% enriched, uranium with 10 wt. % molybdenum (U-10Mo), uranium nitride (UN), and other stable fissionable fuel compounds. Burnable poisons may also be included. Typically, the fissionable nuclear fuel composition is in the form of a ceramic material (cermet), such as UO 2  with W or Mo and UN with W or Mo. When used, a thermal transfer agent, such as a salt or metal that will be molten at operating temperatures, can be included in the fuel element structure to improve thermal coupling between the fuel composition body and the cladding body. Additionally, a thermal transfer agent can occupy cracks or other defects in the fuel element structure (whether originally present or developing during reactor operation) to promote thermal coupling. Suitable molten metals for inclusion in the disclosed nuclear propulsion fission reactor structure and to be included in the fuel element structure to provide thermal transfer contact includes sodium (Na), sodium-potassium (NaK), potassium (K), and iron (Fe). 
     It will also be understood that, although the terms “first” and “second” are used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first image could be termed a second image, and, similarly, a second image could be termed a first image, without departing from the scope of the various described embodiments. The first image and the second image are both images, but they are not the same image. 
     Although some of the various drawings illustrate a number of logical stages in a particular order, stages that are not order dependent may be reordered and other stages may be combined or broken out. While some reordering or other groupings are specifically mentioned, others will be obvious to those of ordinary skill in the art, so the ordering and groupings presented herein are not an exhaustive list of alternatives. Moreover, it should be recognized that the stages could be implemented in hardware, firmware, software, or any combination thereof. 
     Further, the terminology used in the description of the various embodiments described herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed terms. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising” when used in the specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. 
     While reference has been made to specific embodiments, it is apparent that other embodiments and variations can be devised by others skilled in the art without departing from their spirit and scope. The appended claims are intended to be construed to include all such embodiments and equivalent variations.