Abstract:
An additive manufacturing process includes the steps of measuring a parameter of a part supported within a workspace after a heat treat or other stress relieving process. The measured parameter being a part characteristic that is desired to be within a desired range prior to proceeding with an additional fabrication process. The process further includes the step of applying at least one additional layer on the part based on the measured parameter to adjust the measured parameter to within the desired range.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/549,890 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. Repeated localized heating by the laser beam coupled with relatively fast cooling across the surface of the part generates stresses in the part that can limit size and part configuration. 
         [0005]    The stresses may be relieved through heat-treating methods. Once heat-treating is complete, surfaces of the part may shift from the original state and not be straight level and consistent. 
       SUMMARY 
       [0006]    An additive manufacturing process according to an exemplary embodiment of this disclosure including, among outer possible things, measuring a parameter of a part supported within a workspace, the measured parameter required to be within a desired range prior to proceeding with an additional fabrication process and applying at least one additional layer on the part based on the measured parameter to adjust the measured parameter to within the desired range. 
         [0007]    In a further embodiment of the foregoing additive manufacturing process the measured parameter comprises a surface flatness of a top surface of the part. 
         [0008]    In a further embodiment of any of the forgoing additive manufacturing processes measuring a flatness of the part is performed with a laser profilometer. 
         [0009]    In a further embodiment of any of the forgoing additive manufacturing processes measuring a flatness of the part is performed with a measurement device including three-dimensional optics. 
         [0010]    In a further embodiment of any of the forgoing additive manufacturing processes including defining a topography of a top surface of the part based on the measured parameter and defining a pattern of material application based on the defined topography. 
         [0011]    In a further embodiment of any of the forgoing additive manufacturing processes, including applying a powder metal material over a portion of a top surface of the part to generate a top surface with a flatness within the desired range. 
         [0012]    In a further embodiment of any of the forgoing additive manufacturing processes including measuring the measured parameter throughout a stress relieving process. 
         [0013]    In a further embodiment of any of the forgoing additive manufacturing processes including continuing an additive manufacturing process responsive to the measured parameter being within the desired range. 
         [0014]    An additive manufacturing device according to an exemplary embodiment of this disclosure including, among outer possible things a workspace defining an area for part fabrication, a material application device for spreading a powder within the workspace, an energy transmitting device for generating a molten area of powder for forming a layer of a part a measurement device mounted within the workspace for measuring a parameter of the part, and a controller governing application of material to the part to adjust the parameter to within a desired range based on measurements of the parameter by the measurement device. 
         [0015]    In a further embodiment of the foregoing additive manufacturing device the measurement device comprises a laser profilometer. 
         [0016]    In a further embodiment of any of the foregoing additive manufacturing devices the measurement device includes three-dimensional optics. 
         [0017]    In a further embodiment of any of the foregoing additive manufacturing devices the parameter comprises a flatness of a top surface of the part. 
         [0018]    In a further embodiment of any of the foregoing additive manufacturing devices the controller defines topography of a top surface of the part based on measurements taken by the measurement device. 
         [0019]    In a further embodiment of any of the foregoing additive manufacturing devices the controller defines a material application pattern based on the defined topography of the top surface of the part. 
         [0020]    In a further embodiment of any of the foregoing additive manufacturing devices, including elements supported within the chamber for stress relieving the part, and the measurement device provides for continued measurement of the parameter during the process of stress relieving the part. 
         [0021]    A powder bed additive manufacturing process according to an exemplary embodiment of this disclosure including, among outer possible things, monitoring a geometry of an upper surface of a part during a heat treat operation, determining an out of tolerance condition of the geometry, generating a topography of the upper surface in response to determining the out of tolerance condition, and iteratively fusing material with the upper surface in layers based on the topography, thereby flattening the upper surface. 
         [0022]    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. 
         [0023]    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 
         [0024]      FIG. 1  is schematic view of an example additive manufacturing machine. 
           [0025]      FIG. 2  is a schematic view of the example additive manufacturing machine measuring a surface of a part. 
           [0026]      FIG. 3  is an example topographic view of a measured surface of a part. 
           [0027]      FIG. 4  is a schematic view of the example additive manufacturing machine adding material to a top surface of a part. 
           [0028]      FIG. 5  is a schematic view of the example additive manufacturing machine after the part is brought into a desired range. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Referring to  FIG. 1 , an additive manufacturing machine  10  includes a chamber  12  that supports an energy transmitting device  18  and a support  14  on which a part  16  is supported during fabrication. In this example, the energy-transmitting device  18  emits a laser beam  20  that melts material  24  deposited by a material applicator  22 . The example material  24  is a metal powder that is applied in a layer over the support  14  and subsequent layers to produce a desired configuration of the part  16 . The laser beam  20  directs energy that melts the powder material in a configuration that forms the desired part dimensions. 
         [0030]    The additive manufacturing process utilizes material  24  that is applied in layers on top of the support  14 . Selective portions of the layers are subsequently melted by the energy emitted from the laser beam  20 . The additive manufacturing process proceeds by melting subsequent layers of powdered material  24  that are applied to the part  16  to form the desired part configuration. 
         [0031]    As appreciated, the energy focused on the top layer of the part  16  generates the desired heat to melt portions of the powdered metal and/or the part  16 . The relatively small melt pool generated will then solidify based on convection to the surrounding atmosphere of the chamber  12  and/or conduction through the part  16  and the support  14 , thereby forming the desired part configuration. The repeated localized heating and cooling of the powdered material  24  across the top surface  42  of the part  16  can result in the buildup of undesired stresses within the part  16 . Stresses within the part  16  may result in undesired cracking or weaknesses within the completed part and therefore are to be avoided. 
         [0032]    The example additive manufacturing machine  10  includes features that provide for stress relief of the part  16  within the workspace  12 . The features include an electric heater  30  supported within walls of the chamber  12  and a cooler  34  for cooling the part  16  as required for the stress relieve process. Further, the example additive manufacturing machine  10  includes a plurality of sensors  26  that are disposed within the support  14 . In this example, the sensors  26  are strain gauges that measure stress built up within the part  16 . Also provided within the workspace  12  are measuring devices  40 . 
         [0033]    During operating and fabrication of the part  16 , the strain gauges  26  transmit information to a controller  28  that are indicative of the condition and specifically the stress condition of the part  16 . The stress measurements that are provided by the strain gauges  26  are ongoing during the entire fabrication of the part  16 . When measured stress within the part  16  falls outside of desired ranges, the stress relieving process is initiated. In this example, the stress relieving process includes a heat treat process where the part  16  is heated then cooled according to a predetermined temperature and period. 
         [0034]    In this example, the electric resistant heaters  30  embedded in the walls of the chamber  12  emit heat  32  to heat the part  16 . Before the heat treatment process is begun, the chamber  12  may be filled with an inert gas  48  and a cover  19  may be closed to protect the energy transmitting device  18 . In this example, the inert gas  48  is Argon. 
         [0035]    Referring to  FIG. 2 , once the heat treating and/or stress relieving process is complete the heaters  30  and cooler  34  are turned off. The now heat treated part  16  may include a measurable parameter that is not within a desired range preferred for the additive manufacturing process. In this example, the part  16  includes a flatness of the top surface  42  that is schematically shown as being outside of a desired range of flatness. In this example, the top surface  42  includes a peak  36  and valleys  38  that generate the out of range flatness condition. 
         [0036]    Accordingly, the example additive manufacturing machine  10  provides for monitoring geometry of the top surface  42  the part during the heat treat process so that any out of tolerance condition of the geometry can be identified. Once an out of tolerance condition is identified a topography of the top surface is defined. Using the defined topography of the out of tolerance top surface  42  an iterative fusing of material on the upper or top surface  42  by layers is performed based on the topography to flattening the top surface  42 . 
         [0037]    The example additive manufacturing machine  10  includes the measuring devices  40 . In this example, the measurement devices include laser profilometers  40  that measures a parameter of the part  16  that in this example is a top surface flatness. As appreciated, although the example measuring device  40  is a laser profilometer, other measuring devices such as a device that utilized three-dimensional optics or other known measuring and profiling devices. 
         [0038]    Referring to  FIG. 3  with continued reference to  FIG. 2 , the laser profilometers  40  generate a topography  44  of the top surface  42  that is utilized to define a pattern of material deposition to correct for the non-flat condition in order to bring the top surface  42  back to within a desired range of flatness. In this example the peaks  36  and valleys  38  are disposed in a non-uniform manner about the top surface  42 . 
         [0039]    Referring to  FIG. 4  with continued reference to  FIGS. 2 and 3 , the topography  44  of the top surface  42  including the peaks  36  and valleys  38  is utilized by the controller  28  to define a material application protocol. The material application protocol guides the material applicator  22  over the top surface  42  such that it will deposit material primarily on depressions of the top surface  42 , such as the valleys  38  in this example, while skipping or applying a lighter layer over the peaks  36 . Once the material  24  is applied, the energy directing device  18  will direct the laser beam  20  (shown in  FIG. 1 ) to direct energy to build up those areas of the top surface  42  defined by the topography  44  in a given plane. Layer by layer additional material  24  is added to build the top surface  42  to within a desired range of flatness. 
         [0040]    Referring to  FIG. 5 , solidified material  46  deposited in the lower valley areas  38  buildup flatness of the top surface  42  to a desired range determined to provide a proper foundation for further fabrication of the part  16 . The measuring devices  40  may be utilized to verify the top surface in real time after application of each layer or number of layers. Moreover, the controller  28  may execute the defined protocol until complete and then initiate a verifying measurement of the top surface. Once the top surface  42  is within a desired flatness range, further fabrication of the part can begin or restarted. 
         [0041]    Accordingly, the disclosed advanced manufacturing machine and process of addresses changes in part parameters after stress relieving of a part during fabrication such that fabrication may be resumed without removal of the part  16  from the fabrication chamber  12 . 
         [0042]    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.