Abstract:
An integrated additive manufacturing cell (IAMC) that combines conventional manufacturing technologies with additive manufacturing processes is disclosed. Individual IAMCs may be configured and optimized for specific part families of complex components, or other industrial applications. The IAMCs incorporate features that reduce hardware cost and time and allow for local alloy tailoring for material properties optimization in complex components.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates generally to the field of automated manufacturing. More specifically, embodiments of the invention relate to methods and systems for automated manufacturing cells. 
   Turbine and rocket engine components are typically fabricated using a wide variety of manufacturing technologies. Many of the component parts are fabricated using high temperature superalloy materials. These alloys tend to be hard, high strength materials that are difficult, time consuming and expensive to machine. Without resorting to mechanical joining operations, conventional manufacturing processes also limit the material in the workpiece to one specific alloy. 
   Typical manufacturing processes have critical issues that challenge their efficiency. Significant time and cost for component fabrication occurs due to material lead time and hard tooling for complex shapes. Usually, no non-destructive testing (NDT) is included in the automated process. 
   What is needed is an additive manufacturing process that improves product quality and includes processes that require minimal material removal due to the near net shape of the workpiece. The manufacturing process should reduce secondary machining needs and incorporate an architecture that eliminates setup and transfer times due to concurrent secondary machining operations. 
   SUMMARY OF THE INVENTION 
   The inventors have discovered that it would be desirable to have methods and systems that combine conventional manufacturing technologies with additive manufacturing processes in an integrated additive manufacturing cell (IAMC). 
   Individual IAMCs may be configured and optimized for specific part families of turbine and rocket engine components. An IAMC is not limited to aerospace applications and may be used for other industrial applications. The workpiece grown in the IAMC environment may incorporate features such as integral fixturing tabs and stiffening ribs to facilitate part handling and secondary machining operations. The parts will be grown on target plates with transfer and locating features for instant setup on subsequent machine tools such as microwave heat treatment antechambers, concurrent secondary operations, real-time white light surface geometry inspection, real-time non-destructive testing, real-time repair and blended metal powder delivery to the deposition head that reduce hardware cost and time and allow for local alloy tailoring for material properties optimization in engine components. 
   One aspect of the invention provides an additive machining cell system. Systems according to this aspect of the invention comprise an enclosed central manufacturing cell having a plurality of access ports, and a mechanical and electrical port interface associated with each access port, wherein the interface is configured to couple power, communications, and mechanical utilities with an external module. 
   Another aspect of the system is where each external module further comprises an enclosure having a module access port, and a mechanical and electrical module port interface associated with the module access port, wherein the module port interface is configured to couple power, communications, and mechanical utilities in matching correspondence with the central manufacturing cell port interfaces. 
   Another aspect of the system is where the central manufacturing cell houses an additive manufacturing process. 
   Another aspect of the system is where the additive manufacturing process is selected from the group of processes consisting of a powder fed/laser heated melt pool, a wire fed/laser heated melt pool, a powder fed/electron beam heated melt pool, a wire fed/electron beam heated melt pool, or a short circuit gas metal arc. 
   Another aspect is a method of fabricating a component part using an integrated additive manufacturing cell. Methods according to this aspect of the invention preferably start with importing CAD/CAM software files, determining secondary operations necessary for fabricating the component part, coordinating the secondary operations to yield an efficient order of simultaneous and sequential operations, assembling the integrated additive manufacturing cell with modules corresponding to the secondary operations, performing machine instruction coding for each additive manufacturing cell operations wherein one of the operations is an additive manufacturing process, downloading the machine instruction coding into a control system, and fabricating the component part according to the coding. 
   The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exemplary plan view of an integrated additive manufacturing cell (IAMC). 
       FIG. 2  is an exemplary section view of the integrated additive manufacturing cell shown in  FIG. 1  taken along line  2 - 2 . 
       FIG. 3  is an exemplary plan view of an advanced IAMC. 
       FIG. 4  is an exemplary section view of the advanced IAMC shown in  FIG. 3  taken along line  4 - 4 . 
       FIG. 5  is an exemplary multiple station IAMC with secondary machining operations. 
       FIG. 6  is an exemplary advanced two station IAMC. 
       FIG. 7  is an exemplary method of using an IAMC to fabricate a component part with  FIG. 7A  being a first portion of a flowchart and  FIG. 7B  being a second portion of the flowchart. 
   

   DETAILED DESCRIPTION 
   Embodiments of the invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Further, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “mounted,” “connected,” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting, and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
   Additive manufacturing techniques comprise solid freeform fabrication (SFF) methods. These methods produce prototypes of complex freeform solid objects directly from computer models without part-specific tooling or knowledge. These techniques are used for rapid prototyping of mechanical elements. Additive manufacturing typically means fabrication processes that include more than just layered processes, but also related systems of material addition, subtraction, assembly, and insertion of components made by other processes. 
   Additive manufacturing processes are emerging as rapid manufacturing techniques for mass-customized products. These techniques may be effectively used for true manufacturing and decrease the time to manufacture new products. The complexity that may be obtained from SFF parts comes at low cost as compared to other manufacturing processes such as machining. The IAMC system can quickly create a near net shape workpiece of complex geometry. A broad range of conventional metal shaping processes may be replaced, or reduced, to minimal secondary operations. The IAMC simplifies the manufacturing of the difficult to handle refractory super alloys used in high temperature turbine engines and rocket motors. 
   Additive manufacturing processes are similar to building up metal using a conventional weld bead. The difference is the source of the heat which may be a laser or electron beam, and the motion control system that allows shaped parts to be grown. With the exception of cast manufacturing, most conventional manufacturing processes are material reduction processes that remove material from a workpiece using some kind of machining process. In contrast, additive manufacturing processes build up a workpiece by adding material via a weld bead that deposits material in layers. 
   The IAMC incorporates a part family oriented architecture that integrates solid free form fabrication capabilities with mature computer numerical control (CNC) software, state-of-the-art secondary metal working process modules, and a system supervisory software package. The IAMC architecture optimizes both cost and cycle time for producing specific families of components. 
   The ability of the additive manufacturing processes to grow complex geometry near net shape workpieces without tooling enables conventional processes such as casting, forming, forging, rolling, extruding, pressing, stretch forming, milling, turning, drilling, sawing, broaching, shaping, planning, and joining (welding, brazing, bolted joints) or diffusion bonding to be replaced or reduced. The system embodiments may fabricate hardware using the integrated machining and additive processes simultaneously. 
   The IAMC allows near net shaped, aerospace quality workpieces to be fabricated in a matter of hours without hard tooling. These processes exploit the inventory advantages of storing material in powder or wire form until needed. The IAMC integrates part family post-deposition operations such as heat treatment, secondary machining modules (milling, drilling, grinding, broaching, etc.), white light optical inspection techniques, high sensitivity non-destructive evaluation (NDE), process monitoring and control, and continuous process parameter recording. These technologies are integrated with the additive deposition processes to perform feature and finishing operations either simultaneously, or in sequence to allow for the shortest manufacturing time. Simultaneous processing combined with the minimal material removal requirement for a near net shape workpiece allows for part fabrication at unprecedented speeds. 
   One IAMC benefit is a reduction in the number of steps a workpiece must go through from start to finish. This is achieved by the additive manufacturing process fabricating a near net shape workpiece without tooling that only needs minimal subsequent secondary operations. The additive process allows specific fixturing tabs to be grown on the workpiece depending on the subsequent machining operations to simplify part handling. Sophisticated fixturing allows the workpiece to be presented for either subsequent machining operations, or machining operations concomitant with workpiece growth. 
   Shown in  FIGS. 1 and 2  is a first exemplary configuration of an IAMC cell  101 . An additive manufacturing cell (AMC)  103  is the module in the IAMC that performs an SFF or additive deposition, forming the workpiece  102 . The IAMC  101  may include a common cell  104  for combining a number of additional modules such as secondary machining and finishing operation modules  109 ,  111 ,  113 ,  115 . A conventional or microwave heat treatment furnace  107  may be included if necessary for post deposition material stress relief. A robotic workpiece  102  cart  207  effectively couples the AMC  103 , heat treatment furnace  107  and common cell  104  together. 
   The common cell  104  has a plurality of access ports  105  that accept different types of machining modules, or other material manipulation device modules. The geometry of the access ports  105  frames are configured to allow for an air-tight, environmental seal between a module and the common cell  104 . The exemplary common cell  104  is configured as a hexagon in plan view having six access ports  105 , one located per side. Other configurations having any number of ports  105  may be realized. One port may be a workpiece access door  106  for entry to inspect or to remove a workpiece  102  when completed. 
   Each access port  105  frame  106  (not shown) has mechanical and electrical interfaces located in predetermined locations about its periphery for engaging and coupling with corresponding mechanical and electrical interfaces in matching correspondence on a module port frame. The mechanical and electrical interfaces use compatible electrical and mechanical male/female mating couplings needed to support computer, electrical, pneumatic, hydraulic and other machine tool service needs. In an alternative embodiment, to simplify module exchange and placement, a suite of quick disconnect couplings may be installed on interface panels (not shown) near the port frames and mated with precut cables and hoses fitted with the appropriate couplings for coupling a common cell  104  with a module. 
   Each module enclosure has a port frame opening in matching correspondence with the common cell  104  ports  105 . The common cell  104  to module  109 ,  111 ,  113 ,  115  coupling may be performed using a seal, for example a static gasket or inflatable seal, around the frame in conjunction with a bolted or dogged flange arrangement. The electrical interfaces may comprise a 32 bit or higher computer bus for computer control of the machine tool spindles and other motion control functions, module operations, and communications, and single or multi-phase power couplings for module power using quick disconnects. 
   The AMC  103  comprises multiple external hoppers, for example,  203   a ,  203   b ,  203   c ,  203   d  at a high elevation for accepting and containing different metal alloys. In alternative embodiments, wire feed spools may substitute for the hoppers  203   a ,  203   b ,  203   c ,  203   d  to feed material to the deposition melt pool  201 . For powder fed additive manufacturing technologies, the metal powder in the hoppers is delivered to the laser heated melt pool via an atmospherically sealed array of powder transfer mechanisms and conduits  205   a ,  205   b ,  205   c  that terminate at the deposition head. 
   The AMC  103  may use several technologies, for example, a powder fed/laser heated melt pool, a wire fed/laser heated melt pool, a powder fed/electron beam heated melt pool, a wire fed/electron beam heated melt pool, a short circuit gas metal arc, or other free form techniques.  FIG. 2  shows the IAMC  101  using an exemplary powder fed/laser heated melt pool embodiment. Any additive manufacturing technology may be located and employed in the AMC  103 . 
   The IAMC  101  allows for creating a near, net shape workpiece without needing to relocate the workpiece to different work site locations or facilities. The additional secondary operational modules may house equipment such as the heat treatment/stress relief antechamber  107 , a non-destructive testing (NDT) and measurement sensor suite  109 , and a suite of secondary machine tools  111 ,  113 ,  115  that mate to the common cell  104  via the mechanical and electrical interface  106 . The secondary operation machine tool suite  104 ,  109 ,  111 ,  113 ,  115  is decided by a specific part, or part family, that each IAMC  101  is tailored for. Typical secondary, separate operations that may be performed in an operation module  109 ,  111 ,  113 ,  115  include drilling, milling, turning, grinding, broaching, reaming, shot peening, grit blasting, and polishing. 
   After a workpiece is grown in the AMC  103  in accordance with CAD/CAM programming instructions executed by a main control system (not shown), the near net-shape completed workpiece may be transferred by the robotic cart  207  ( FIG. 2 ) from the AMC  103  to the heat treatment oven  107  for post-growth stress relief of the deposition process induced residual thermal stresses in the workpiece. During workpiece growth, predetermined fixturing tabs are grown to allow subsequent machining operations to grab and manipulate the workpiece, if necessary, for positioning the workpiece when performing their machining operations. After stress relief, the workpiece  102  may be transferred  207  to the common cell  104  for secondary machining operations. The robotic cart  207  positions the workpiece  102  in the center of the cell  104  where each predetermined machining module may access the workpiece under three-axis computer control to perform its preprogrammed secondary machining operations either in sequence, or in one or more simultaneous activities. The simultaneous operations are coordinated when determining the part to be fabricated and the number of discrete operations that are necessary for part construction. After secondary operations are finished, one of the modules  109 ,  111 ,  113 ,  115  may perform a part inspection. Afterwards, any remaining fixturing tabs are removed, and the access door  106  opened allowing the robotic cart  207  to remove the finished workpiece  102 . 
   The level of integration shown in  FIGS. 1 and 2  capitalizes on additive manufacturing processes, computer process control, metallurgical property control, shape-making capability, surface finish capability and real-time inspection and repair capability. 
   The AMC  103  may be refined to the point that no secondary operations may be required, meaning that the needed shape making, tolerances, and surface finish requirements will be within the capability of the AMC  103  itself. 
   Shown in  FIGS. 3 and 4  is an exemplary advanced IAMC  301  embodiment. In this embodiment, the IAMC  301  includes secondary operations within the AMC  303 . In addition to SFF, the AMC  303  may include laser beam machining (LBM) or laser assisted dry machining. 
   Laser beam machining is accomplished by precisely manipulating a laser beam to vaporize unwanted, deposited material. LBM includes cutting, welding, drilling, heat-treating, scoring and scribing materials at a very high speed and in a very precise specification. Multiple, simultaneous secondary operations may be performed in the same additive manufacturing environment without contaminating or compromising the material SFF deposition while in-progress. 
   While a workpiece is being grown during SFF, laser beam machining may provide heat treatment prior to the deposition area and immediately after, using a plurality of beam pulses and durations, thereby controlling the thermodynamic profile of the pre and post deposition metal. The material micro structure and residual thermal stresses will be effectively controlled in real-time as the part is grown. Laser heat-treatment is a surface alteration process that changes the microstructure of metals by controlled heating and cooling. The laser, because of its ability to pinpoint focus both the amount and the location of its energy, can heat treat small sections or strips of material without affecting the metallurgical properties of the surrounding area. Laser heat-treating advantages include precision control of heat input to localized areas, minimum distortion, minimum stress and micro cracking, self-quenching, and is an inherently time efficient process. 
   Laser scribing may be performed where lines may be produced on the workpiece while SFF is ongoing. The line being laser scribed is only as wide as a single laser beam and is set to a specific tolerance depth. The line consists of a series of small, closely spaced holes in the substrate that is produced by laser energy pulses. 
   The AMC  303  similarly includes multiple hoppers  303   a ,  303   b ,  303   c ,  303   d  for accepting and containing the different metal alloys for powder fed additive manufacturing technologies. When the workpiece has been grown to a predetermined size, a movable separation barrier, if needed for contamination control of the deposition process, may be positioned just below the growth surface of the workpiece. The separation barrier may or may not be needed depending on specific workpiece geometry and the nature of the machining operations being performed. Rough machining operations may be performed on a lower part of the workpiece simultaneously with the growth of the workpiece by the additive manufacturing system used. The AMC performs the function of growing the near net shape workpiece. Afterwards, the workpiece is cut off or separated from the target plate and a final inspection is performed. 
   Post stress relief is performed in a conventional, or microwave heat treat oven  107 . Secondary, simultaneous machining operations may be performed. The IAMC  301  AMC  303  may include a number of additional modules such as conventional secondary machining and finishing operation modules  109 ,  111 ,  113 ,  115 . The AMC  303  is the central and common manufacturing cell and has a plurality of access ports  305  that accept the different types of machining modules, or other material manipulation device modules as previously described. 
   The IAMC  301  allows for creating a near, net shape workpiece without needing to relocate the workpiece. The additional operational modules may house equipment such as a heat treatment/stress relief antechamber  107 , a nondestructive testing (NDT) and measurement sensor suite  109 , and a suite of secondary machine tools  111 ,  113 ,  115  that mate to the cell via the mechanical and electrical interface  106 . The secondary operation machine tool suite is decided by a specific part, or part family, that each IAMC  101  is configured for. Typical secondary operations that may be performed in an operation module include drilling, milling, turning, grinding, broaching, reaming, shot peening, grit blasting, and polishing. 
   Two additional alternative IAMC fabrication embodiments are shown in  FIGS. 5 and 6 , and teach IAMC configurations that depend on a desired component architecture which in turn defines the level of IAMC integration. The lowest level of integration is a group technology work cell that locates machine tools adjacent to each other to minimize transfer time of the workpiece ( FIG. 5 ). Medium level integration shown in  FIGS. 1 and 2  (previously discussed), combines conventional secondary processes, but leaves the additive manufacturing cell independent. The highest level of integration is shown in  FIG. 6  and combines as many operations as possible in the minimum number of individual cells. The highest level uses one or more advanced IAMC embodiments that are shown in  FIGS. 3 and 4  such that secondary machining operations may be progressively conducted just below the growth surface of the workpiece and laser tailoring of the thermodynamic profile of melt pool solidification will perform heat treating and stress relief operations as they occur. 
   For the embodiment shown in  FIG. 5 , a multiple station IAMC  501  fabricates a near net shape workpiece in an AMC  103 . Afterwards, the workpiece is stress relieved in a microwave stress relief chamber  107 . Additional machining operations are performed sequentially  109 ,  111 ,  113 ,  115 ,  505 ,  507 ,  509  in post, dedicated group technology work cells. This may include part family specific operations such as milling, drilling, grinding, shot peening, broaching, turning, grit blasting, polishing and other conventional machining operations. 
   After all machining and treatment operations are performed, the workpiece is separated/removed from a target plate. The target plate for this class of additive manufacturing processes may be the same metal alloy as the material being deposited. 
   Shown in  FIG. 6  is an advanced multiple IAMC  601  architecture employing two advanced IAMCs  303   1 ,  303   2 . Each advanced IAMC  303   1 ,  303   2  may work the workpiece  102  depending on the level of complexity of machining an initial growth workpiece, and the need to add more material and additional secondary machining operations. A robotic cart  207  may be used to transfer the workpiece  102  from one advanced IAMC  303   1  to another  303   2 . Alternatively, the both advanced IAMCs  303   1 ,  303   2  may be coupled together such that the robotic transfer cart  207  travels within a tunnel between the IAMCs  303   1 ,  303   2  to maintain an inert, purged condition. 
   For simplicity, the IAMC embodiment shown in  FIGS. 1 and 2  will be used to illustrate the method shown in  FIG. 7 . A desired component part is created via CAD/CAM software files and the files are imported to the IAMC (step  705 )( FIG. 7A ). The operations necessary to fabricate the part are derived (step  710 ) and listed in an order of operations such as growth, post growth stress relief, surface machining, drilling and tempering (peening), for example (step  715 ). The individual operation modules (stress relief, surface machining, drilling and peening) are coupled; environmentally, mechanically, and electrically, to the common cell  104  and the robotic cart  207  with target plate is positioned (step  720 ). The order of operations, the operations which may be performed simultaneously, and the instructions for each module are coded, and downloaded to the control system (step  725 ). 
   The control system executes the instructions and begins growing the workpiece (step  730 )( FIG. 7B ). After the growth, the workpiece may be moved and heat treated (annealed)(step  735 ) to relieve stress prior to having the surface machined (step  740 ). After annealing, the workpiece may be moved into the common cell for secondary machining operations. A white light inspection may be performed using machine vision to determine the amount of material needed to be removed to bring the part within acceptable tolerances (step  745 ). If needed, an optional abrasive machining may be performed (step  750 ) followed with a deburring operation (step  755 ). One or more of the operations (steps  740 ,  745 ,  750 ,  755 ,  760 ,  765 ) may be performed simultaneously. The workpiece may be cleaned (step  760 ) in a wash down module and inspected (step  765 ) prior to being removed from the common cell. The cell configuration and the supervising software will be constructed to allow as many operations to be performed simultaneously as possible. 
   Methods for the advanced IAMC may be implemented similarly, except that the AMC program handles more secondary machining operations due to its laser machining. 
   One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.