Abstract:
An additive manufacturing machine includes a base plate for supporting fabrication of a desired part geometry. The base plate includes a support portion defined based on the desired part geometry and an open region that includes a plurality of openings surrounding the support portion. A material applicator deposits material onto the base plate and an energy directing device directs energy to form the deposited material into a desired part geometry. The additive manufacturing machine manages large amounts of material required for fabricating the part by defining a boundary surrounding a periphery of a desired part geometry and forming a retaining wall along the defined boundary and the desired part geometry to retain excess material between the formed wall and the part. Excess material outside of the retaining wall falls through the open area below the base plate and is reclaimed for reuse.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/549,868 which was filed on Oct. 21, 2011. 
     
    
     BACKGROUND 
       [0002]    This disclosure generally relates to an LASER configuration for an additive manufacturing machine and process. More particularly, this disclosure relates to a configuration for relieving stress within a part during creation within the additive manufacturing assembly. 
         [0003]    Typical manufacturing methods include various methods of removing material from a starting blank of material to form a desired completed part shape. Such methods utilize cutting tools to remove material to form holes, surfaces, overall shapes and more by subtracting material from the starting material. Such subtractive manufacturing methods impart physical limits on the final shape of a completed part. Additive manufacturing methods form desired part shapes by adding one layer at a time and therefore provide for the formation of part shapes and geometries that would not be feasible in part constructed utilizing traditional subtractive manufacturing methods. 
         [0004]    Additive manufacturing utilizes a heat source such as a laser beam to melt layers of powdered metal to form the desired part configuration layer upon layer. The laser forms a melt pool in the powdered metal that solidifies. Another layer of powdered material is then spread over the formerly solidified part and melted to the previous melted layer to build a desired part geometry layer upon layer. Powdered material that is applied but not melted to become a portion of the part accumulates around and within the part. For smaller parts the excess powdered material is not significant. However, as capabilities improve and larger parts are fabricated, the excess powdered metal may become significant consideration in both part fabrication capabilities and economic feasibility. 
       SUMMARY 
       [0005]    An additive manufacturing process according to an exemplary embodiment of this disclosure include the steps of defining a boundary surrounding a periphery of a desired part geometry, depositing material onto a base plate and directing energy to portions of the deposited material for forming a retaining wall along the defined boundary and the desired part geometry. 
         [0006]    In a further embodiment of the foregoing additive manufacturing process the deposited material is retained between the retaining wall and the periphery of the part. 
         [0007]    In a further embodiment of any of the foregoing additive manufacturing processes deposited material outside the retaining wall is removed from the workspace. 
         [0008]    In a further embodiment of any of the foregoing additive manufacturing processes, including reclaiming the removed deposited material and depositing the reclaimed material onto at least one of the part and the retaining wall 
         [0009]    In a further embodiment of any of the foregoing additive manufacturing processes, including building the retaining wall in concert with the part such that a top layer of the retaining wall and a top layer of the part are substantially within a common plane. 
         [0010]    A further embodiment of any of the foregoing additive manufacturing processes, including heating at least one of the part and the retaining wall to a desired temperature greater than ambient temperature and less than a temperature required to melt the deposited material. 
         [0011]    A further embodiment of any of the foregoing additive manufacturing processes, including heating the retaining wall with a defocused laser. 
         [0012]    A further embodiment of any of the foregoing additive manufacturing processes, including heating the part with the defocused laser. 
         [0013]    A further embodiment of any of the foregoing additive manufacturing processes, including heating at least one of the part and the retaining wall with heating elements supported proximate the retaining wall. 
         [0014]    A further embodiment of any of the foregoing additive manufacturing processes, including heating at least one of the part and the retaining wall with heat transmitted through the base plate. 
         [0015]    A further embodiment of any of the foregoing additive manufacturing processes, including cutting the base plate to include a support portion for supporting the retaining wall and the part and a grid portion for evacuating excess deposited material. 
         [0016]    An additive manufacturing machine according to an exemplary embodiment of this disclosure, among other possible things includes a base plate for supporting fabrication of a desired part geometry, wherein the base plate includes a support portion defined based on the desired part geometry and an open region surrounding the support portion, the open regions including a plurality of openings, a material applicator for depositing material onto the base plate, and an energy directing device for forming a portion of the deposited material. 
         [0017]    In a further embodiment of the foregoing additive manufacturing machine, the open region comprises a grid open to a space below the base plate. 
         [0018]    In a further embodiment of any of the foregoing additive manufacturing machine, the support portion is shaped to correspond to an outer periphery of the desired part geometry and a retaining wall spaced apart from the outer periphery of the desired part geometry. 
         [0019]    In a further embodiment of any of the foregoing additive manufacturing machine, including at least one secondary energy-directing device emitting a defocused laser beam for heating portions of at least one of the part and the retaining wall. 
         [0020]    In a further embodiment of any of the foregoing additive manufacturing machine, including a workspace defined by walls including heating elements for regulating a temperature within the workspace. 
         [0021]    In a further embodiment of any of the foregoing additive manufacturing machine, including plate includes a heating element for heating a part during fabrication. 
         [0022]    In a further embodiment of any of the foregoing additive manufacturing machine, including a recirculating system for gathering excess material flowing through the open regions of the base plate. 
         [0023]    Although the different examples have the specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
         [0024]    These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is schematic view of an example additive manufacturing machine. 
           [0026]      FIG. 2  is a schematic view of a base plate for the example additive manufacturing machine. 
           [0027]      FIG. 3  is a schematic view of the example additive manufacturing machine including a material reclaiming system. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Referring to  FIG. 1 , an additive manufacturing machine  10  includes a work space  12  that supports an energy transmitting device  18  and a base plate  14  on which a part  40  is supported during fabrication. In this example, the energy-transmitting device  18  emits a laser beam  20  that melts material  30  deposited by a material applicator  28 . The example material  30  is a metal powder that is applied in a layer over the base plate  14  and subsequent layers are applied to produce a desired configuration of the part  40 . The laser beam  20  directs energy that melts the powder material in a configuration that forms the desired part dimensions. 
         [0029]    The additive manufacturing process utilizes material  30  that is applied in layers on top of the base plate  14 . Selective portions of the layers are subsequently melted by the energy emitted from the laser beam  20 . The energy focused on the top layer of the part  40  generates the desired heat to melt portions of the powdered metal. Conduction of heat through the solidified portions of the part and convection cooling to the ambient environment solidifies the melded portions to build and grow the part  40 . The melting and solidification process is repeated layer by layer to build the part  40 . 
         [0030]    The powder  30  that is not utilized or melted to form the part  40  accumulates along the base plate  14  and around the part  40 . In previous additive manufacturing systems the quantity of excess material was insignificant. Fabrication of parts  40  of a larger size accumulate a significant amount of excess non-utilized material the workspace  12  and therefore becomes a significant consideration both economically and to the part configuration. 
         [0031]    In the disclosed example additive manufacturing machine  10 , the base plate  14  includes a support portion  34  that supports the part  40  and a retaining wall  42 . Surrounding the support portion  34  is an open area  36  through which material  30  may fall into a space below the base plate  14 . 
         [0032]    The example open areas  36  include a plurality of through holes  56 . In this example the through holes  56  maybe drilled, cut by a water jet cutter or formed by any other known process. The number and size of the holes  56  is such as to provide sufficient structure to hole the support portion  34  with a sufficient rigidity, while also providing for powdered material to pass through the base plate  14 . Moreover, the open areas  36  of the base plate  14  could also be fabricated using any method or configuration that provides sufficient porosity to allow the metal powder to pass there through. 
         [0033]    During fabrication of the part  40 , the retaining wall  42  is fabricated in conjunction with an outer perimeter and geometry of the part  40 . The retaining wall  42  is formed of the same powder material as the part  40  and is melted by the laser beam  20 . The beam  20  sweeps across both the part  40  and the retaining walls  42  as is indicated by the arrows  32 . The retaining walls  42  are provided to maintain a gap  54  between the part  40  and the inner periphery of each of the retaining walls  42  that is filled with powder material  30 . The walls  42  are of a thickness  52  that is determined to provide the strength required for retaining loose material between the part  40  and the retaining wall  42 . In this example, the retaining wall is approximately 0.25 inch (6.35 mm) thick and the gap  54  between the part  40  and the retaining wall  42  is approximately 0.5 inch (12.7 mm) away from the outermost perimeter of the part  40 . As should be understood, retaining walls of different thickness and spaced apart from the perimeter of the part  40  are also within the contemplation of this disclosure. 
         [0034]    The base plate  14  includes the support portion  34  that is cut away in a shape that corresponds with an outer perimeter of the part  40 . The open portions  36  include a plurality of openings  56  to allow for the material  30  to fall there through. 
         [0035]    Referring to  FIG. 2  with continued reference to  FIG. 1 , the example support plate  14  is includes the open portions  36  that surround the support portion  34 . The support portion  34  is disposed in a shape that corresponds with the desired part configuration. The retaining walls  42  are spaced apart from the outer perimeter of the part  40 . The width  54  defines the space between the retaining wall  42  and the part  40  within which powdered material accumulates. 
         [0036]    The width of the wall  52  is provided to maintain the strength required to support the wall along with the material accumulating between the part and the wall itself. In this example the wall  42  is of a uniform width  52 . However, the wall may be tapered such that the width  52  would vary. Such a tapered retaining wall  42  would include a wider base that thinned as both retaining wall  42  and part  40  grew in height. 
         [0037]    Fabrication of the part  40  proceeds with the application of material  30  over successive layers. Both the part  40  and the retaining wall  42  are held at a temperature less than the melting temperature of the material but higher than room temperature to facilitate melting and solidification of portions of the part  40 . Moreover, maintaining an elevated temperature of the part  40  can aid in reducing the build-up of stresses during the fabrication process. Accordingly the disclosed additive manufacturing machine  10  includes features for heating both the part  40  and the retaining walls  42  to a desired temperature during fabrication. 
         [0038]    Referring again to  FIG. 1 , the chamber  12  includes heating elements  46  that are disposed within walls  16  surrounding the workspace  12 . The heating elements  46  generate a radiant heat  58  that maintains the entire workspace  12  at a desired temperature. 
         [0039]    Also included within the disclosed additive manufacturing machine  10  is secondary energy emitting devices  22  and  26 . Each of the secondary energy emitting devices  22  comprises a laser beam generating device that generates a defocused laser that emits energy to the outer surfaces of the retaining wall  42  as is indicated by the beam regions  24   a . The secondary energy directing devices  22  may also direct energy over the top surface of both the part  40  and the retaining wall  42  as is indicated by beam region  24   b . The defocused laser provides for heating and maintenance of a temperature of the part  40  in the retaining wall  42  without melting material or interfering with the fabrication of the part  40  that is conducted by the primary energy emitting device  18 . Each of these features are controlled by a controller  38  that governs operation of the heating elements  46  and the energy emitting devices  18 ,  22  and  26 . 
         [0040]    The example additive manufacturing machine  10  also includes a heater  48  that provides a heating flow  50  within the support portion  34 . The heating flow  50  maintains the support portion  34  at a desired temperature to aid in maintaining a temperature of the part  40  during fabrication. The heating flow  50  conducts heat from the bottom up through the part  40  to maintain a temperature desired for fabrication. 
         [0041]    The process of fabrication utilizing the disclosed example additive manufacturing machine  10  includes the step of defining the support portion  34  by generating a profile to correspond with an outer periphery of the desired part geometry. The corresponding size of the support portion  34  is also configured to accommodate a buffer area to support the retaining wall  42  that will be fabricated in concert with the part  40 . 
         [0042]    Once the example support portion  34  is defined, it is assembled into the additive manufacturing machine  10  and fabrication may begin. Fabrication begins by dispersing material  30  onto the support portion  34  with the applicator  28 . The energy emitting device  18  emits the laser beam  20  over the support portion  34  to selectively melt material  30  and/or the part  40  and/or the support portion  34 . Upon cooling, the melted material, part and/or support portion fuse and/or solidify integrally. The retaining wall  42  and the part  40  are fabricated at the same time and in concert with each other. Material  30  that falls between the retaining wall  42  and the part  40  remains loose within this region. The retaining wall  42  and part  40  are heated to a temperature desired to provide specific desired fabrication parameters. This temperature maintains the material at a heated condition to lessen the effects of the heating and cooling process conducted by the laser beam  20 . The laser beam  20  sweeps in a direction indicated by arrows  32  as commanded by the controller  38  to provide the desired part geometry. Moreover, the controller  38  also includes instructions to define the retaining wall  42  about the part  40 . 
         [0043]    Referring to  FIG. 3 , the example additive manufacturing machine  10  is shown with the part  40  and the retaining walls  42  during a later fabrication stage where both the retaining wall  42  and the part  40  are of a greater height. As the retaining wall  42  and part  40  increases in size the devices that provide for the warming and maintenance of the temperature of the part  40  become more important. In the disclosed embodiment, heating of the outer retaining walls  42  provides for a conduction of heat through the loose material  44  disposed within the gap  54  such that the part  40  is maintained at a desired temperature. 
         [0044]    In the disclosed embodiment, the process continues with simultaneous fabrication of the retaining wall  42  surrounding the part  40  and the part  40 . Excess material  30  falls between and is maintained between a retaining wall  42  and the part  40 . Material that falls outside of the retaining wall  42  falls through the open area  36  and is gathered by a catch device  60 . The catch device  60  also includes a return line  62  such that the material that is recovered through the open areas  36  can be utilized and routed back to the applicator  28  for further use and fabrication of the part  40  and the retaining wall  42 . Once the part  40  is completed it is removed from the support portion  34  along with the retaining walls  42  according to known methods. 
         [0045]    The example additive manufacturing machine disclosed includes features for maintaining part integrity during fabrication while managing the large amounts of material  30  that are utilized and that flow through the workspace  12  during the fabrication process. Moreover, the example additive manufacturing system includes features for reclaiming the unused powder material that falls through the open areas  36  into the catch  60 . The catch  60  is part of a reclaiming system that reclaims the unused powdered material for use in subsequent operations or in the disclosed embodiment in the current operation and fabrication of a part. Alternatively, the catch  60  may be utilized in concert to a return line  62  that immediately reuses the material by the applicator  28 . 
         [0046]    Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the scope and content of this invention.