Abstract:
An additive manufacturing system includes an energy gun having a plurality of energy source devices each emitting an energy beam. A primary beam melts a selected region of a substrate into a melt pool and at least one secondary beam heat-conditions the substrate proximate the melt pool to reduce workpiece internal stress and/or enhance micro-structure composition of the workpiece.

Description:
[0001]    This application claims priority to U.S. Patent Appln. No. 61/936,652 filed Feb. 6, 2014. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to an additive manufacturing system and, more particularly, to an additive manufacturing system with a multi-energy beam gun and a method of operation. 
         [0003]    Traditional additive manufacturing systems include, for example, Additive Layer Manufacturing (ALM) Systems, such as Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM), Laser Beam Melting (LBM) and Electron Beam Melting (EBM) that provide for the fabrication of complex metal, alloy, polymer, ceramic and composite structures by the freeform construction of the workpiece, layer-by-layer. The principle behind additive manufacturing processes involves the selective melting of atomized precursor powder beds by a single directed energy source, producing the lithographic build-up of the workpiece. The energy source is focused and targeted onto localized regions of the powder bed producing small melt pools, followed by rapid solidification. This melting and solidification process is repeated many times to folio a single layer of the workpiece. Once a layer is completed, the powder bed is spread over the completed solidified layer and the process repeats as part of the layer-by-layer fabrication of the workpiece. These systems are typically directed by a three-dimensional model of the workpiece developed in a Computer Aided Design (CAD) software system. 
         [0004]    The EBM System utilizes a single electron beam gun and the DMLS, SLM, and LBM Systems utilize a single laser as the energy source. Both system beam types are focused by a lens, then deflected by an electromagnetic scanner or rotating mirror so that the energy beam selectively impinges on the powder bed. The EBM System uses a beam of electrons accelerated by an electric potential difference and focused using electromagnetic lenses that selectively scan the powder bed. 
         [0005]    Known ALM Systems have limited control over the heating and cooling cycles of the melt pools that can impact microstructure development of the workpiece and further lead to poor workpiece composition characteristics and properties. 
       SUMMARY 
       [0006]    An energy gun of an additive manufacturing system for producing a workpiece from a substrate according to one, non-limiting embodiment of the present disclosure includes a plurality of energy beams constructed and arranged to follow one-another. 
         [0007]    In a further embodiment of the foregoing embodiment the plurality of energy beams includes a first energy beam for producing a melt pool from the substrate and a second energy beam for post heating to control a solidification rate of the melt pool. 
         [0008]    In the alternative or additionally thereto, in the foregoing embodiment, the plurality of energy beams includes a first energy beam for producing a melt pool from the substrate and a second energy beam for pre-heating the substrate associated with the melt pool. 
         [0009]    In the alternative or additionally thereto, in the foregoing embodiment, the substrate is a powder. 
         [0010]    In the alternative or additionally thereto, in the foregoing embodiment, the plurality of energy beams have different frequencies. 
         [0011]    In the alternative or additionally thereto, in the foregoing embodiment, the gun further includes a plurality of energy source devices wherein each one of the plurality of energy source devices emits a respective one of the plurality of energy beams. 
         [0012]    In the alternative or additionally thereto, in the foregoing embodiment, the plurality of energy sources have fiber optic outputs. 
         [0013]    In the alternative or additionally thereto, in the foregoing embodiment, each one of the plurality of energy beams impart a hot spot upon the substrate at pre-arranged distances from one-another and the plurality of energy source devices are constructed and arranged to move the hot spots in unison across the substrate at a controlled velocity. 
         [0014]    In the alternative or additionally thereto, in the foregoing embodiment, the gun includes a lens for focusing at least one of the plurality of energy beams. 
         [0015]    In the alternative or additionally thereto, in the foregoing embodiment, the plurality of energy beams are focused by the lens and the distance between the hot spots is dictated by the lens. 
         [0016]    In the alternative or additionally thereto, in the foregoing embodiment, the gun includes a housing constructed and arranged to move at the controlled velocity, and the lens is stationary with respect to the housing and the plurality of energy source devices are constructed and arranged to move with respect to the housing to control the distance between the hot spots. 
         [0017]    In the alternative or additionally thereto, in the foregoing embodiment, fiber optic outputs of each one of the plurality of energy source devices are pivoted to produce the movement of the plurality of energy source devices. 
         [0018]    In the alternative or additionally thereto, in the foregoing embodiment, the gun includes a housing constructed and arranged to move at the controlled velocity, a plurality of lenses wherein the lens is one of the plurality of lenses, and each one of the plurality of lenses are supported by and stationary with respect to the housing and focus a respective one of the plurality of energy beams, and wherein the plurality of energy source devices are constructed and arranged to move with respect to the housing to control the distance between the hot spots. 
         [0019]    In the alternative or additionally thereto, in the foregoing embodiment, the gun includes a beam combinatory, and at least one of the plurality of energy beams of respective at least one energy source devices being reflected upon the beam combinator and at least one of the plurality of energy beams of respective at least one energy source devices are refracted upon the beam combinator. 
         [0020]    In the alternative or additionally thereto, in the foregoing embodiment, the combinator is orientated between the plurality of energy source devices and the lens. 
         [0021]    In the alternative or additionally thereto, in the foregoing embodiment, the gun includes a housing constructed and arranged to move at the controlled velocity, and wherein the lens and beam combinator are supported by and stationary with respect to the housing, and wherein at least one of the energy source devices is constructed and arranged to move with respect to the housing to control the distance between the hot spots. 
         [0022]    In the alternative or additionally thereto, in the foregoing embodiment, the gun includes a housing constructed and arranged to move at the controlled velocity, a plurality of lenses wherein the lens is one of the plurality of lenses, and wherein each one of the plurality of lenses are supported by and stationary with respect to the housing, focus a respective one of the plurality of energy beams of each respective energy source device, and are located between the beam combinator and the respective energy source device, and wherein at least one of the plurality of energy source devices are constructed and arranged to move with respect to the housing to control the distance between the hot spots. 
         [0023]    An additive manufacturing system according to another, non-limiting, embodiment includes a primary energy beam for selectively melting a powder layer into a melt pool, a secondary energy beam for heat conditioning the substrate proximate to the melt pool, and a build table for supporting the powder layer. 
         [0024]    A method of additively manufacturing a workpiece according to another, non-limiting, embodiment includes the steps of melting a substrate into a melt pool with a first energy beam, and heat conditioning the substrate with a second energy beam. 
         [0025]    In a further embodiment of the foregoing embodiment, the method includes the step of pre-heating a region of the substrate with the second energy beam before melting the region into the melt pool by the first energy beam. 
         [0026]    The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in-light of the following description and the accompanying drawings. It should be understood; however, that the following description and figures are intended to be exemplary in nature and non-limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiments. The drawings that accompany the detailed description can be briefly described as follows: 
           [0028]      FIG. 1  is a schematic view of an additive manufacturing system according to one non-limiting embodiment of the present disclosure; 
           [0029]      FIG. 2  is a schematic view of an energy gun of the additive manufacturing system; 
           [0030]      FIG. 3  is a schematic view of the energy gun having adjustably moveable energy source devices; 
           [0031]      FIG. 4  is a schematic view of a second embodiment of an energy gun; 
           [0032]      FIG. 5  is a schematic view of a third embodiment of an energy gun; 
           [0033]      FIG. 6  is an enlarge schematic view of a beam combinator of the energy gun of  FIG. 5 ; and 
           [0034]      FIG. 7  is a schematic view of a fourth embodiment of an energy gun. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 1  schematically illustrates an additive manufacturing system  20  according to one non-limiting example of the present disclosure that may have a build table  22  for holding a powder bed  24 , a particle spreader or wiper  26  for spreading the powder bed  24  over the build table, an energy gun  28  for selectively melting regions of a layer of the powder bed, a powder supply hopper  30  for supplying powder to the spreader  26 , and a powder surplus hopper  32 . The additive manufacturing system  20  may be constructed to build a workpiece  36  in a layer-by-layer fashion. 
         [0036]    A controller  38  may have an integral CAD system for modeling the workpiece  36  into a plurality of slices  40  additively built atop one-another generally in a vertical or z-coordinate direction (see arrow  42 ). Once manufactured, each solidified slice  40  corresponds to a layer  44  of the powder bed  24  prior to solidification. The layer  44  is placed on top of a build surface  46  of the previously solidified slice  40 . The controller  38  generally operates the entire system through a series of electrical and/or digital signals  48  sent to the system  20  components. For instance, the controller  38  may send a signal  48  to a mechanical piston  50  of the supply hopper  30  to sequentially push a supply powder  52  upward for receipt by the spreader  26 , or alternatively or in addition thereto, the supply hopper  30  may feed powder downward via gravity. The spreader  26  may be a wiper, roller or other device that pushes (see arrow  54 ) or otherwise places the supply powder  52  over the build surface  46  of the workpiece  38  by a pre-determined thickness established through downward movement (see arrow  42 ) of the build table  22  controlled by the controller  38 . Any excess powder  56  may be pushed into the surplus hopper  32  by the spreader  26 . It is further contemplated and understood that the layer  44  may not be composed of a powder but may take the form of any substrate that may be layed or applied across the build surface  46  in preparation for melting. 
         [0037]    Once a substantially level powder layer  44  is established over the build surface  46 , the controller  38  may send a signal  48  to the energy gun  28  to activate and generally move along the top layer  44  at a controlled velocity and direction (see arrow  58 ) and thereby selectively melt the top layer  44  on a region-by-region basis into melt pools. Referring to  FIGS. 1 and 2 , the energy gun  28  may have a housing  60 , a primary energy source device  62  for emitting a primary energy beam  64 , a secondary energy device  66  for emitting a secondary energy beam  68  for heat conditioning, and a lens  70  for focusing the energy beams  64 ,  68  upon the layer  44  and identified as respective hot spots  72 ,  74  on the layer. In  FIG. 2 , the devices  62 ,  66  and lens  70  are supported by, and held stationary with respect to, the housing  60 . Each energy source device  62  may further include fiber optic outputs  76  that emit and direct the energy beams  64 ,  68 . 
         [0038]    The energy beams  64 ,  68  may be substantially parallel to one-another prior to being refracted through the lens  70 . Once refracted and focused, the beams are redirected to form the hot spots  72 ,  74  at a pre-determined distance  76  away from one-another. That is, the lens  70  is chosen to establish the desired distance  76  between the hot spots. As illustrated, the primary hot spot  72  is the location of the desired melt pool region of the powder layer  44 , and the secondary hot spot  74  is the desired location for post heating, thereby controlling the cool down rate (or solidification rate) of the melt pool. Control of the solidification rate may be desired to reduce internal stresses of the workpiece and/or control microstructure development such as directional grain structure as, for example, that found in single crystal alloys. The pre-established distance  76  is dependent upon many factors that may include but is not limited to the powder composition, the power of the energy source devices  62 ,  64 , the velocity of the energy gun  28 , and other parameters. 
         [0039]    It is further contemplated and understood that the energy beams  64 ,  68  may be laser beams, electron beams or any other energy beams capable of heating the powder to sufficient temperatures and at sufficient rates. Each beam may operate with different frequencies to meet manufacturing objectives. For instance, beams with shorter wavelengths may heat up the powder faster than beams with longer wavelengths. Different optical frequencies or wavelengths typically requires different types of lasers; for example, CO 2  lasers, diode lasers, and fiber lasers. However, to pre-select the best wavelength (thus laser type) for heating and/or melting, the wavelength selected may be based on the composition of the metal powder (for example). That is, particles of a powder may have different heat absorption rates impacting melting rates and solidification rates. Moreover, and besides wavelength, other properties of the beam may be a factor. For instance, pulsed laser beams or continuous laser beams may be desired to melt the powder. It is also understood that by interchanging the two energy source devices  62 ,  64 , the secondary energy source device  64  may be used to pre-heat the desired region to be melted as oppose to post heating. Yet further the heat gun  28  may have two secondary energy source devices that both follow the primary source device for pre-heating and post-heating, respectively. 
         [0040]    Referring to  FIG. 3 , the energy gun  28  may be further capable of moving the energy source devices  62 ,  64  in a tilting movement with respect to the housing  60  (see arrows  78 ) and generally along the same imaginary plane that contains the respective hot spots  72 ,  74 . Controlled tilting of the devices  62 ,  64  may then adjust the distance  76  between the hot spots  72 ,  74  for any given parameters. With devices  62 ,  64  have adjustable tilt capability, the distance  76  is not (or is less) dependent upon the choice of lenses  70 . It is further contemplated and understood that with a three dimensional lens  70 , the movement of the energy source devices  62 ,  64  may also be three dimensional, thus enabling move complex operations of the system  20 . Yet further, it is contemplated that movement of the energy source devices  62 ,  66  may be limited to the fiber optic outputs  76 , thereby relying on the routing capability and flexibility of the fiber optic technology. 
         [0041]    Referring to  FIG. 4 , a second, non-limiting, embodiment of the energy gun is illustrated wherein like components to the first embodiment have like identifying numerals except with the addition of a prime symbol. The energy gun  28 ′ of the second embodiment has a first lens  70 ′ for focusing a primary energy beam  64 ′ of a primary energy source device  62 ′. A second lens  80  focuses an energy beam  68 ′ of a secondary energy source device  66 ′. Both lenses  70 ′,  80  are supported by, and may be stationary with respect to, a housing  60 ′ and the devices  62 ′,  66 ′ are constructed and arranged to move or pivot to adjust a distance  76 ′ between hot spots  72 ′,  74 ′. 
         [0042]    Referring to  FIGS. 5 and 6 , a third, non-limiting, embodiment of the energy gun is illustrated wherein like components to the first embodiment have like identifying numerals except with the addition of a double prime symbol. The energy gun  28 ″ of the third embodiment has a beam combinator  82  positioned between a lens  70 ″ and primary and secondary energy source devices  62 ″,  66 ″. The combinator  82  is supported by a housing  60 ″ and is positioned at a prescribed angle  84  with respect to the lens  70 ″ and/or a powder layer  44 ″. The angle  84  may be about forty-five degrees with the primary energy source  62 ″ located above the combinator  82  such that an energy beam  64 ″ emitted from the device  62 ″ is directed downward and refracted, first through the combinator  82  and then through the lens  70 ″. The device  62 ″, the combinator  82  and the lens  70 ″ may be supported by and stationary with respect to the housing  60 ″. The secondary energy source device  66 ″ may be positioned such that a secondary energy beam  68 ″ is adjustably directed horizontally to reflect off of the combinator  82  and then refracted through the lens  70 ″. 
         [0043]    Device  66 ″ may be supported by the housing  60 ″ and may also be constructed and arranged to pivot, tilt, or move with respect to the housing such that the beam  68 ″ is adjustably reflected off of the beam combinator  82 . As best shown in  FIG. 6 , a distance  76 ″ between hot spots  72 ″,  74 ″ may be adjusted by changing the incident reflection angle upon the combinator  82 . More specifically, the beam  68 ″ may have a large reflection angle  86  producing a large distance between hot spots  72 ″,  74 ″. Moving or pivoting the energy source device  66 ″ to produce a smaller reflection angle  88  will reduce the distance  76 ″ between hot spots  72 ″,  74 ″. It is further contemplated and understood that the reflected beam  68 ″ may be held stationary and the energy source device  62 ″ emitting the energy beam  64 ″ may be adjustably pivoted or moved to adjust the refraction angle thereby adjusting the distance  76 ″. 
         [0044]    Referring to  FIG. 7 , a fourth, non-limiting embodiment of an energy gun is illustrated wherein like elements to the second and third embodiments have like identifying numerals except with the addition of a triple prime symbol. In the fourth embodiment, an energy gun  28 ′″ has a primary energy beam  64 ′″ that is first focused through a lens  70 ′″ and then refracted through a beam combinator  82 ′″. A secondary energy beam  68 ′″ is first focused through a second lens  80 ′″ and then reflected off of the combinator  82 ′″. A secondary energy source device  66 ′″, emitting the secondary energy beam  68 ′″, may be constructed and arranged to pivot or move with respect to a housing  60 ′″ to adjust a distance  76 ′″ between respective hot spots  72 ′″,  74 ′″. 
         [0045]    Referring to  FIG. 6  and in operation as step  100 , a CAD system as part of the controller  38  models the workpiece  36  in a slice-by-slice, stacked orientation. As step  102 , a powder bed layer  44  is spread directly over the build table  22  per signals  48  sent from the controller  38 . As step  104 , the energy gun  28  then melts on a melt pool by melt pool basis a pattern upon the layer  44  mimicking the contour of a bottom slice  76  of the plurality of slices  40  as dictated by the controller  38 . As step  106 , the melted portion of the powder layer solidifies over a pre-designated time interval thereby completing the formation of a bottom slice  76 . As step  108 , the controller  38  communicates with the controller  96  of the ultrasonic inspection system  34  and the controller  96  initiates performance of an inspection to detect defects  66  in the bottom slice  76 . As step  110  and if a defect is detected, the controllers communicate electronically with one-another and the bottom slice  76  is reformed by re-melting and re-solidification. 
         [0046]    As step  112 , a powder bed layer  44  is spread over the defect-free bottom slice  76 . As step  114 , at least a portion of the layer is melted by the energy gun  28  along with a meltback region of the solidified bottom layer  76  in accordance with a CAD pattern of a top slice dictated by the controller  38 . As step  116  the melted layer solidifies forming the top slice  88  and a uniform and homogeneous interface  64 . As step  118 , the controller  38  communicates with the controller  96  and another ultrasonic inspection is initiated sending ultrasonic waves  82  through the bottom slice  76  and into the top slice  88 . As step  120 , the ultrasonic waves are in-part reflected off of any defects and in-part off of the build surface  46  of the top layer  88 , received by the array  70  and processed by computer software. As step  122  and if a defect is detected, such as a delamination defect at the interface  64 , the top slice  88  along with the meltback region is re-melted and re-solidified to remove the defects. The system  20  may then repeat itself forming yet additional slices in the same manner described and until the workpiece  36  is completed. 
         [0047]    It is understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude and should not be considered otherwise limiting. It is also understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will also benefit. Although particular step sequences may be shown, described, and claimed, it is understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
         [0048]    The foregoing description is exemplary rather than defined by the limitations described. Various non-limiting embodiments are disclosed; however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims It is therefore understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For this reason, the appended claims should be studied to determine true scope and content.