Abstract:
An additive manufacturing apparatus includes: a build module comprising a build chamber, and a least one of but less than all of the following elements: (a) a directed energy source; (b) a powder supply; (c) a powder recovery container; and (d) a powder applicator; and a workstation comprising the remainder of elements (a)-(d) not included in the build module.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to an additive manufacturing apparatus and more particularly to an apparatus for mass production of components. 
         [0002]    “Additive manufacturing” is a term used herein to describe a process which involves layer-by-layer construction or additive fabrication (as opposed to material removal as with conventional machining processes). Such processes may also be referred to as “rapid manufacturing processes”. Additive manufacturing processes include, but are not limited to: Direct Metal Laser Melting (DMLM), Laser Net Shape Manufacturing (LNSM), electron beam sintering, Selective Laser Sintering (SLS), 3D printing, such as by inkjets and laserjets, Sterolithography (SLA), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), and Direct Metal Deposition (DMD). 
         [0003]    Currently, powder bed technologies have demonstrated the best resolution capabilities of prior art metal additive manufacturing technologies. However, since the build needs to take place in the powder bed, conventional machines use a large amount of powder, for example a powder load can be over 130 kg (300 lbs.). This is costly when considering a factory environment using many machines. The powder that is not directly melted into the part but stored in the neighboring powder bed is problematic because it adds weight to the elevator systems, complicates seals and chamber pressure problems, is detrimental to part retrieval at the end of the part build, and becomes unmanageable in large bed systems currently being considered for large components. 
         [0004]    Furthermore, currently available additive manufacturing systems are geared for prototyping and very low volume manufacturing. Considerable differences can exist from part-to-part. Some elements of current systems are cumbersome to handle due to weight and can require excessive manual, hands-on interaction. Duplication of multiple machines in parallel to manufacturing multiple parts results in expensive duplication of components and services such as controls and cooling and environmental controls. 
         [0005]    Accordingly, there remains a need for an additive manufacturing apparatus and method that can produce components on a mass-production basis. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    This need is addressed by the technology described herein, which provides additive manufacturing apparatus utilizing one or more simplified build modules in combination with one or more common components being centrally provided or shared amongst the build modules. 
         [0007]    According to one aspect of the technology described herein an additive manufacturing apparatus includes: a build module having a build chamber, and a least one of but less than all of the following elements: (a) a directed energy source; (b) a powder supply; (c) a powder recovery container; and (d) a powder applicator; and a workstation having the remainder of elements (a)-(d) not included in the build module. 
         [0008]    According to another aspect of the technology described herein, an additive manufacturing apparatus includes: a workstation including a directed energy source; a build module, including: a first build chamber; and a peripheral wall extending past the worksurface opposite the first build chamber to define a workspace; and a transport mechanism operable to move the build module into and out of the workstation. 
         [0009]    According to another aspect of the technology described herein, an additive manufacturing method includes: moving a build module having a build chamber into a workstation; depositing powder onto a build platform which is disposed in the build chamber; directing a beam from a directed energy source to fuse the powder; moving the platform vertically downward within the build chamber by a layer increment of powder; and repeating in a cycle the steps of depositing, directing, and moving to build up the part in a layer-by-layer fashion until the part is complete 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures, in which: 
           [0011]      FIG. 1  is a cross-sectional view of an additive manufacturing build module constructed according to an aspect of the technology described herein; 
           [0012]      FIG. 2  is a top plan view of the build module of  FIG. 1 ; 
           [0013]      FIG. 3  is a cross-sectional view of an alternative additive manufacturing build module; 
           [0014]      FIG. 4  is a top plan view of the build module of  FIG. 3 ; 
           [0015]      FIG. 5  is a schematic side view of the build module of  FIG. 1  in an assembly line; 
           [0016]      FIG. 6  is a schematic side view of an alternative build module in an assembly line; 
           [0017]      FIG. 7  is a schematic side view of the build module of  FIG. 3  in an assembly line; 
           [0018]      FIG. 8  is a cross-sectional view of an alternative additive manufacturing build module; and 
           [0019]      FIG. 9  is a schematic top plan view of the build module of  FIG. 8  in a rotary assembly center. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    In general, aspects of the technology described herein provide an additive manufacturing apparatus and method in which multiple build modules are used in an assembly-line process. The individual build modules are simplified compared to prior art additive machines and may be configured to include only the components needed to manufacture a specific part or selected group of parts, with common components being centrally provided or shared amongst the build modules. 
         [0021]    Now, referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIGS. 1 and 2  illustrate an exemplary additive manufacturing build module  10  for carrying out a manufacturing method according to one aspect of the technology described herein. The build module  10  incorporates a worksurface  12 , a powder supply  14 , an applicator  16 , a build chamber  18  surrounding a build platform  20 , and a powder recovery container  22 . Each of these components will be described in more detail below. 
         [0022]    The worksurface  12  is a rigid structure and is coplanar with and defines a virtual workplane. In the illustrated example, it includes a build chamber opening  24  communicating with the build chamber  18 , a supply opening  26  communicating with the powder supply  14 , and a recovery opening  28  communicating with the powder recovery container  22 . The module  10  includes a peripheral wall  30  extending past the worksurface  12  so as to define a workspace  32 . The worksurface  12  is surrounded by the peripheral wall  30  of the build module  10 . Optionally, as shown in  FIG. 1 , the workspace  32  is closed off by a removable or openable window  34  that is transparent to radiant energy, for example, the window  34  could be made of glass. As shown in  FIG. 6 , the window  34  may be eliminated depending on the desired process configuration. 
         [0023]    The applicator  16  is a rigid, laterally-elongated structure that lies on or contacts the worksurface  12  and is moveable in the workspace  32  positioned above the worksurface  12 . It is connected to an actuator  36  operable to selectively move the applicator  16  parallel to the worksurface  12 . The actuator  36  is depicted schematically in  FIG. 1 , with the understanding devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. As depicted, the applicator  16  moves from right to left to move powder from the powder supply  14  to the build chamber  18  with excess powder being moved to the powder recovery container  22 . It should be appreciated that the powder supply  14  and powder recovery container  22  may be reversed and the applicator  16  may move from left to right to supply powder from the powder supply  14  to the build chamber  18 . 
         [0024]    The powder supply  14  comprises a supply container  38  underlying and communicating with supply opening  26 , and an elevator  40 . The elevator  40  is a plate-like structure that is vertically slidable within the supply container  38 . It is connected to an actuator  42  operable to selectively move the elevator  40  up or down. The actuator  42  is depicted schematically in  FIG. 1 , with the understanding that devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. When the elevator  40  is lowered, a supply of powder “P” of a desired alloy composition may be loaded into the supply container  38 . When the elevator  40  is raised, it exposes the powder P above the worksurface  12  to allow the applicator  16  to scrape the exposed powder into the build chamber  18 . It should be appreciated that the powder used in the technology described herein may be of any suitable material for additive manufacturing. For example, the powder may be a metallic, polymeric, organic, or ceramic powder. 
         [0025]    The build platform  20  is a plate-like structure that is vertically slidable in the build chamber  18  below the opening  24 . The build platform  20  is secured to an actuator  44  that is operable to selectively move the build platform  20  up or down. The actuator  44  is depicted schematically in  FIG. 1 , with the understanding that devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. 
         [0026]    The powder recovery container  22  underlies and communicates with the recovery opening  28 , and serves as a repository for excess powder P. 
         [0027]    The build module  10  may be implemented in different configurations. For example, build module  100 ,  FIGS. 3-4 , includes a worksurface  112 , a powder supply  114 , an applicator  116 , a first build chamber  118  surrounding a first build platform  120 , a second build chamber  150  surrounding a second build platform  152 , a first powder recovery container  122 , and a second powder recovery container  154 . 
         [0028]    The worksurface  112  is a rigid structure and is coplanar with and defines a virtual workplane. In the illustrated example, it includes a first build chamber opening  124  communicating with the build chamber  118 , a second build chamber opening  156  communicating with the build chamber  150 , a central supply opening  126  communicating with the powder supply  114 , a first recovery opening  128  communicating with the first powder recovery container  122 , and a second recovery opening  158  communicating with the second powder recovery container  154 . The module  100  includes a peripheral wall  130  extending past the worksurface  112  so as to define a workspace  132 . The worksurface  112  is surrounded by the peripheral wall  130  of the build module  100 . Optionally, as shown in  FIG. 1 , the workspace  132  may be closed off by a removable or openable window  134  that is transparent to radiant energy, for example, the window  134  could be made of glass. As discussed above, depending on the desired setup, the window  134  may be eliminated. 
         [0029]    The applicator  116  is a rigid, laterally-elongated structure that lies on the worksurface  112  and is moveable in the workspace  132  positioned above the worksurface  112 . It is connected to an actuator  136  operable to selectively move the applicator  116  along the worksurface  112 . The actuator  136  is depicted schematically in  FIG. 3 , with the understanding devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. The applicator  116  operates in like fashion to applicator  16  except that applicator  116  moves right from a first starting location  88  to move powder from powder supply  114  to build chamber  118  and moves left from a second starting location  90  to move powder from powder supply  114  to build chamber  150 . 
         [0030]    The powder supply  114  comprises a supply container  138  underlying and communicating with supply opening  126 , and an elevator  140 . The elevator  140  is a plate-like structure that is vertically slidable within the supply container  138 . It is connected to an actuator  142  operable to selectively move the elevator  140  up or down. The actuator  142  is depicted schematically in  FIG. 3 , with the understanding that devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. When the elevator  140  is lowered, a supply of powder “P” of a desired alloy composition may be loaded into the supply container  138 . When the elevator  140  is raised, it exposes the powder P above the worksurface  112 . It should be appreciated that the powder used in the technology described herein may be of any suitable material for additive manufacturing. For example, the powder may be a metallic, polymeric, organic, or ceramic powder. 
         [0031]    Build platforms  120  and  152  are plate-like structures that are vertically slidable in build enclosures  118  and  150 , respectively, below openings  124  and  156 . The build platforms  120  and  152  are secured to actuators  144  and  160  that are operable to selectively move the build platforms  120  and  152  up or down. The actuators  144  and  160  are depicted schematically in  FIG. 3 , with the understanding that devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. 
         [0032]    The powder recovery containers  122  and  154  underlie and communicate with overflow openings  128  and  158 , respectively, and serve as a repository for excess powder P. 
         [0033]    Build module  10  and build module  100  may each include a respective gas port  62 ,  162  and a respective vacuum port  64 ,  164  extending through the peripheral wall  30 ,  130 . The gas ports  62 ,  162  allow workspaces  32  and  132  to be purged with an appropriate shielding gas while the vacuum ports  64 ,  164  allow the workspaces  32  and  132  to be cleared of loose powder contained in the volume of the workspaces  32  and  132 . This ensures that the workspaces  32  and  132  and windows  34  and  134  remain clean during operation. 
         [0034]    As illustrated in  FIGS. 5-7 , the build modules  10  and  100  are configured to produce a single part or a limited number of parts in a small package, such that the build modules  10  and  100  may be easily lifted and placed on a conveyor  70  or other suitable transport mechanism, thus allowing a plurality of build modules to be positioned in an assembly line to manufacture a plurality of parts in sequence. In operation the conveyor  70  is used to move the build modules into a workstation  71 . As illustrated in  FIG. 5 , the workstation  71  may be defined as a physical location within the overall additive manufacturing system. At the workstation  71 , a directed energy source  72  positioned above the conveyor  70  may be used to melt powder P and form a part  86 . 
         [0035]    The directed energy source  72  may comprise any device operable to generate a beam of suitable power and other operating characteristics to melt and fuse the powder during the build process, described in more detail below. For example, the directed energy source  72  may be a laser. Other directed-energy sources such as electron beam guns are suitable alternatives to a laser. 
         [0036]    A beam steering apparatus  74  is used to direct the energy source and comprises one or more mirrors, prisms, and/or lenses and provided with suitable actuators, and arranged so that a beam “B” from the directed energy source  72  can be focused to a desired spot size and steered to a desired position in an X-Y plane coincident with the worksurface  12 ,  112 . 
         [0037]    In cases where windows  34  and  134  are employed, the workstation  71  may be an open area, as seen in  FIGS. 5 and 7 . This is possible because the build modules  10 ,  100  are completely enclosed and include the gas and vacuum ports described above. 
         [0038]    The overall system may include one or more central services, such as a central ventilation system  78  to supply shielding gas and/or forced ventilation to shield the build process and purge powder entrained in the build enclosure  76 , a central cooling system  79  to provide cooling fluid to the directed energy source  72 , and/or an electronic central controller  80  to provide control for the build process, for example by driving the directed energy source  72  and various functions of the workstation  71  and/or build module  10 . The central services  78 ,  79 ,  80  may be coupled to multiple workstations  71  as part of an overall production system. The individual connections to central services may be made manually or using automated connection devices when the build modules  10 ,  100  are moved into place in the workstation  71 . 
         [0039]    Alternatively, if the build modules  10 ,  100  are employed without windows  34 ,  134 , the conveyor  70  may be used to transport the build modules  10 ,  100  into a workstation  71 ′ having a build enclosure  76  which provides a closed environment. The build enclosure  76  may include sealing elements  82 ,  84  (e.g. curtains, flaps, or doors) to allow the build modules  10 ,  100  to pass therethrough and seal off the build enclosure  76  once the build module  10 ,  100  has entered or exited the build enclosure  76 . The central services described above (e.g. central ventilation system  78 , central cooling system  79 , and/or central controller  80 ) would be coupled to the enclosure  76 . 
         [0040]    For purposes of clarity, only build module  10  will be discussed below. It should be appreciated that while the build module  100  is of a different configuration than build module  10 , the build process for build module  100  is essentially the same process except for the movement of the applicator  116  (which moves from center to right and center to left with the center position being a starting position) and the fact that more than one build chamber is being utilized to form multiple parts in a single build module. 
         [0041]    The build process for a part  86  using the build module  10  described above is as follows. The build module  10  is prepared by loading the powder supply  14  with powder P. This is done by lowering the elevator  40  using actuator  42  to a position below the worksurface  12  and loading enough powder P onto the elevator  40  to build part  86 . Once the build module  10  is prepared, the build module  10  is positioned on conveyor  70  for transport to the directed energy source  72 . Because the build module  10  is a self-contained unit and is easily moved onto and off of the conveyor  70 , multiple build modules may be positioned onto the conveyor  70  to provide an assembly line of build modules. 
         [0042]    Once the conveyor  70  has transported the build module  10  to the directed energy source  72 ,  FIGS. 5-6 , the build process may begin. The build platform  20  is moved to an initial high position. The initial high position is located below the worksurface  12  by a selected layer increment. The layer increment affects the speed of the additive manufacturing process and the resolution of the part  86 . As an example, the layer increment may be about 10 to 50 micrometers (0.0003 to 0.002 in.). Powder “P” is then deposited over the build platform  20 . For example, the elevator  40  of the supply container  38  may be raised to push powder through the supply opening  26 , exposing it above the worksurface  12 . The applicator  16  is moved across the worksurface  12  to spread the raised powder P horizontally over the build platform  20 . Any excess powder P is pushed along the worksurface  12  and dropped into powder recovery container  22  as the applicator  16  passes from right to left. It should be appreciated that the configuration of the build module  10  may be reversed, i.e., by switching the locations of the powder supply  14  and powder recovery container  22 . Subsequently, the applicator  16  may be retracted back to a starting position. 
         [0043]    For build module  100 , build platforms  120  and  152  are moved to the initial high position and the elevator  140  is raised to push powder through supply opening  126 . Applicator  116  moves from the first central position  88  across the worksurface  112  to spread powder P horizontally over the build platform  120  with excess powder P deposited in powder recovery container  122 . Applicator  116  is moved to the second central position  90 , elevator  140  is raised to push powder P through supply opening  126 , and applicator  116  moves across worksurface  112  to spread the powder P over the build platform  152  with excess powder deposited in powder recovery container  154 . Applicator is moved back to the first central position  88 . The steps described below with respect to build platform  20  also apply to build platforms  120  and  152 . 
         [0044]    The directed energy source  72  is used to melt a two-dimensional cross-section or layer of the part  86  being built. The directed energy source  72  emits a beam “B” and the beam steering apparatus  74  is used to steer the focal spot “S” of the beam B over the exposed powder surface in an appropriate pattern. The exposed layer of the powder P is heated by the beam B to a temperature allowing it to melt, flow, and consolidate. This step may be referred to as fusing the powder P. 
         [0045]    The build platform  20  is moved vertically downward by the layer increment, and another layer of powder P is applied in a similar thickness. The directed energy source  72  again emits a beam B and the beam steering apparatus  74  is used to steer the focal spot S of the beam B over the exposed powder surface in an appropriate pattern. The exposed layer of the powder P is heated by the beam B to a temperature allowing it to melt, flow, and consolidate both within the top layer and with the lower, previously-solidified layer. 
         [0046]    This cycle of moving the build platform  20 , applying powder P, and then directed energy melting the powder P is repeated until the entire part  86  is complete. 
         [0047]    Once the part  86  is complete, the conveyor  70  moves the build module  10  away from the directed energy source  72  to allow a user to remove the build module  10  from the conveyor  70 , remove the part  86  from the build module  10 , and prepare the build module  10  to build another part  86 . It should be appreciated that multiple build modules may be placed on the conveyor  70  so that when one part  86  is complete, the conveyor moves another build module  10  into position to complete another part  86 . 
         [0048]    An alternative build module is illustrated in  FIG. 8  and shown generally at reference numeral  200 . Build module  200  represents another configuration of build module  10 . Build module  200  includes a worksurface  212 , a build chamber  218  surrounding a build platform  220 , and a powder recovery container  222 . 
         [0049]    As discussed above with respect to build module  10 , the worksurface  212  is a rigid structure and is coplanar with and defines a virtual workplane. In the illustrated example, it includes a build chamber opening  224  for communicating with the build chamber  218  and exposing the build platform  220  and a recovery opening  228  communicating with the powder recovery container  222 . 
         [0050]    The build platform  220  is a plate-like structure that is vertically slidable in the build chamber  218  below the opening  224 . The build platform  220  is secured to an actuator  244  that is operable to selectively move the build platform  220  up or down. The actuator  244  is depicted schematically in  FIG. 8 , with the understanding that devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. 
         [0051]    The powder recovery container  222  underlies and communicates with the recovery opening  228 , and serves as a repository for excess powder P. 
         [0052]    The build module  200  is designed to work with an additive manufacturing apparatus  300 ,  FIGS. 8 and 9 , having a build enclosure  310  and a rotary turntable  370 . The build enclosure  310  houses a powder supply  314 , an applicator  316 , a directed energy source  372 , and a beam steering apparatus  374 . The build enclosure  310  encloses a portion of the rotary turntable  370 . 
         [0053]    The rotary turntable  370  incorporates a worksurface  312  that provides a rigid structure and is coplanar with worksurface  212  to define a virtual workplane. In the illustrated example, it includes a plurality of build module openings  392  spaced around the rotary turntable  370  for permitting a build module  200  to be positioned by a user in each of the plurality of build module openings  392 . The rotary turntable  370  may be rotated using known methods such as gears, motors, and other suitable methods. 
         [0054]    The powder supply  314  comprises a supply container  338  in the form of a hopper having a narrow spout  394  for dropping powder P onto the worksurface  312 . A metering valve  396  is positioned in the narrow spout  394  and is configured to drop a pre-determined amount of powder P. The amount of powder P dropped by the metering valve  396  is based on the size of the build platform  220  and a layer increment (described above with reference to build module  10 ) used during a build process. 
         [0055]    The applicator  316  is a rigid, laterally-elongated structure that lies on and traverses worksurfaces  212  and  312 . It is connected to an actuator  336  operable to selectively move the applicator  316  along the worksurfaces. The actuator  336  is depicted schematically in  FIG. 8 , with the understanding devices such as pneumatic or hydraulic cylinders, ballscrew or linear electric actuators, and so forth, may be used for this purpose. As depicted, the applicator  316  moves from left to right to move powder from the powder supply  314  to the build chamber  218  with excess powder being moved to the powder recovery container  222 . It should be appreciated that the configuration of the powder supply  314 , directed energy source  372 , build chamber  218 , and powder recover container  222  may be reversed and the applicator  316  may move from right to left to supply powder from the powder supply  314  to the build chamber  218 . 
         [0056]    The directed energy source  372  may comprise any known device operable to generate a beam of suitable power and other operating characteristics to melt and fuse the powder during the build process, described in more detail below. For example, the directed energy source  372  may be a laser. Other directed-energy sources such as electron beam guns are suitable alternatives to a laser. The beam steering apparatus  374  is used to direct the energy source and comprises one or more mirrors, prisms, and/or lenses and provided with suitable actuators, and arranged so that a beam “B” from the directed energy source  372  can be focused to a desired spot size and steered to a desired position in an X-Y plane coincident with the worksurface  212 ,  312 . 
         [0057]    The build process for a part  186  begins by positioning a build module  200  into one of the plurality of build module openings  392 . Multiple build modules may be positioned on the rotary turntable  370  by positioning a build module  200  in each build module opening  392 . As illustrated, the rotary turntable  370  includes eight build module openings  392 . It should be appreciated that the number of build module openings may be changed based on the size and application of the rotary turntable  370 . 
         [0058]    With the build module  200  positioned in the build module opening  392 , the rotary turntable  370  is rotated to position the build module  200  in a build position,  FIG. 8 , so as to allow the applicator  316 , powder supply  314 , and directed energy source  372  to form the part  186 . As discussed above, the build platform  220  is moved to an initial high position. The initial high position is located below the worksurface  212  by a selected layer increment. The metering valve  396  of the powder supply  314  is actuated to drop a pre-determined amount of powder P from the powder supply  314  onto the worksurface  312 . The applicator  316  is moved across the worksurface  312  and the worksurface  212  to spread the dropped powder P horizontally over the build platform  220 . Any excess powder P is pushed along the worksurface  212  and dropped into powder recovery container  222 . The applicator  316  may be moved back to its initial position. 
         [0059]    The directed energy source  372  is used to melt a two-dimensional cross-section or layer of the part  186  being built. The directed energy source  372  emits a beam “B” and the beam steering apparatus  374  is used to steer the focal spot “S” of the beam B over the exposed powder surface in an appropriate pattern. The exposed layer of the powder P is heated by the beam B to a temperature allowing it to melt, flow, and consolidate. This step may be referred to as fusing the powder P. 
         [0060]    The build platform  220  is moved vertically downward by the layer increment, and another layer of powder P is applied in a similar thickness. The directed energy source  372  again emits a beam B and the beam steering apparatus  374  is used to steer the focal spot S of the beam B over the exposed powder surface in an appropriate pattern. The exposed layer of the powder P is heated by the beam B to a temperature allowing it to melt, flow, and consolidate both within the top layer and with the lower, previously-solidified layer. 
         [0061]    This cycle of moving the build platform  220 , applying powder P, and then directed energy melting the powder P is repeated until the entire part  186  is complete. 
         [0062]    Once the part  186  is complete, the rotary turntable  370  rotates to move the build module  200  away from the directed energy source  372  to allow a user to remove the build module  200  from the rotary turntable  370  and replace it with another build module  200 . The part  186  is removed from the build module  200  and the build module  200  may be prepared to build another part  186 . It should be appreciated that multiple build modules may be placed on the rotary turntable  370  so that when one part  186  is complete, the rotary turntable  370  rotates another build module  200  into position to complete another part  186 . 
         [0063]    The additive manufacturing apparatus and method described above has several advantages over the prior art. It is compatible with a closed powder handling system, eliminates the need for a large open powder reservoir to make multiple parts, and saves significant labor in handling excess powder after a build cycle. 
         [0064]    The foregoing has described an additive manufacturing apparatus and method. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
         [0065]    Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
         [0066]    The invention is not restricted to the details of the foregoing embodiment(s). The invention extends any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.