Abstract:
An apparatus and method for additive manufacturing components. Build powder is deposited on a build platform in accordance with CAD data, and surrogate powder is deposited in regions where the build powder is not located in order to conserve build powder. An energy source traces over the build powder fusing the build powder into a first layer of the component. The build platform is then lowered so that another layer of powder may be deposited on top of the first layer. This process is repeated until a final component is completed. The surrogate powder is then removed; thus, conserving build powder.

Description:
BACKGROUND 
       [0001]    Additive manufacturing is a method used for producing geometrically complex components. This type of manufacturing utilizes directed energy to melt powder that is deposited on a platform. A first layer of powder is uniformly deposited on the build platform, and then the directed energy melts a first layer of the component. Then another layer of powder is uniformly deposited onto the first layer. The directed energy fuses this layer to the first layer. This process is repeated until a three-dimensional component is complete. Once the process is complete, the component is removed from the build platform, and the remaining powder left and not melted on the build platform is ideally recycled to be used again for another part. However, the recycling of the unused powder is often time-consuming, tedious, and labor intensive. It currently requires a manual reclamation of the powder via vacuuming or sweeping. The powder must then go through a sifting process in sieves in an attempt to ensure that no large particulates were collected in the vacuuming or sweeping. Then the powder is reloaded into an additive manufacturing machine to be used again to build another component. The additional and costly labor required to recycle the powder is typically substantial in relation to the operation time and cost incurred by the additive manufacturing machine. Additionally, the additive manufacturing machine cannot be used during the recycling process, so the turn-around time for an additive manufacturing machine is increased, allowing for fewer components to be made in a given period of time. 
         [0002]    Another disadvantage of current systems and methods of additive manufacturing is the quality of recycled powder. The quality of an additively manufactured component is directly related to the quality of the powder. It is wasteful to throw unused powder away, but often the quality of the recycled powder is diminished after going through the additive manufacturing process and recycling. Each time the powder is recycled, the recycled powder&#39;s size distribution, chemistry, and morphology are inferior compared to the original powder. It is currently unknown how many times powder can be recycled before its quality is decreased to the point that it cannot be used again. This raises concerns with respect to the ability to use recycled powder for critical components. Thus, additive manufacturing for these types of applications may require additional, stringent powder recycling procedures, such as recertification of any recycled powder before being reloaded into an additive manufacturing machine for subsequent use. The recertification process can be lengthy and expensive. 
         [0003]    This background discussion is intended to provide information related to the present invention which is not necessarily prior art. 
       SUMMARY 
       [0004]    Embodiments of the present invention solve the above-mentioned problems and provide a distinct advance in the art of additive manufacturing using recycled powders. An additive manufacturing apparatus constructed in accordance with embodiments of the invention may be used in a method of additive manufacturing that does not waste powder and does not rely on a quality of powder remaining constant after being recycled several times. The method may include a step of selectively depositing various types of powder, such as build powder and surrogate powder, in separate regions on a build platform. Then the method may include a step of selectively melting the build powder, while not tracing over or melting the surrogate powder, creating a first layer of a component being formed. This process is repeated one or more times, sequentially forming and fusing a plurality of layers of the component together until the component is finished. Then the method may include a step of removing the surrogate powder from the build platform. 
         [0005]    In some embodiments of the invention, the deposition of the powders and/or the selective melting described above may be computer-controlled in accordance with a computer-aided design (CAD) model, or other technical model or drawing. Furthermore, a plurality of components may also be simultaneously manufactured using the methods described herein. The surrogate powder may include, for example, casting sand, which is then recycled and used in subsequent additive manufacturing processes. The build powder may be any number of materials such as metals, metal alloys, ceramics, plastics, etc. 
         [0006]    According to another embodiment of the invention, the additive manufacturing apparatus may include a powder deposition device, a build platform, a directed energy source a first actuator, a second actuator, a third actuator, and a controller. The powder deposition device may have at least two chambers and at least one nozzle for dispensing various types of powder, including a surrogate powder and a build powder. The build platform may include a horizontally-extending base and vertical-extending walls surrounding the base. The first actuator may actuate the base relative to the wall along a center axis of the base, the second actuator may actuate movement of the directed energy source relative to the build platform, and the third actuator may actuate movement of the nozzle relative to the build platform. The controller may be communicably coupled with various other components of the additive manufacturing apparatus, and may command the actuators. Specifically, the controller may command the third actuator and the powder deposition device to selectively deposit the surrogate powder and the build powder in different regions on the build platform, and then command the directed energy source and the second actuator to selectively melt only the build powder on the build platform. The selective melting is performed without fusing any surrogate powder by tracing the directed energy source over the regions on the build platform having the build powder deposited thereon, thereby forming a layer of the component. Then the controller may command the first actuator to lower the build platform relative to the wall, and may repeat the forming of another layer of the component, thus sequentially forming and fusing a plurality of layers of the component together. 
         [0007]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures. 
     
    
     
       DRAWINGS 
         [0008]    Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein: 
           [0009]      FIG. 1  is an apparatus in accordance with an embodiment of the present invention; 
           [0010]      FIG. 2  is a top view of the apparatus of  FIG. 1 ; 
           [0011]      FIG. 3  is a perspective view of a build platform of the apparatus of  FIG. 1 ; 
           [0012]      FIG. 4  is a side view of a powder deposition device of the apparatus of  FIG. 1 , moving relative to the build platform; 
           [0013]      FIG. 5  is a top view of the powder deposition device of  FIG. 4 ; and 
           [0014]      FIG. 6  is a flowchart of a method of additive manufacturing in accordance with an embodiment of the present invention. 
       
    
    
       [0015]    The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. 
       DETAILED DESCRIPTION 
       [0016]    The following detailed description of embodiments of the invention references the accompanying figures. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those with ordinary skill in the art to practice the invention. Other embodiments may be utilized and changes may be made without departing from the scope of the claims. The following description is, therefore, not limiting. The scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
         [0017]    In this description, references to “one embodiment”, “an embodiment”, or “embodiments” mean that the feature or features referred to are included in at least one embodiment of the invention. Separate references to “one embodiment”, “an embodiment”, or “embodiments” in this description do not necessarily refer to the same embodiment and are not mutually exclusive unless so stated. Specifically, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, particular implementations of the present invention can include a variety of combinations and/or integrations of the embodiments described herein. 
         [0018]    Embodiments of the invention, illustrated in  FIGS. 1-6 , include surrogate powder  10  used in an additive manufacturing apparatus  12  and a method  100  of additive manufacturing using the surrogate powder  10 . As illustrated in  FIG. 1 , the additive manufacturing apparatus  12  may comprise a multi-material powder hopper  16 , a plurality of actuators  20 , a powder deposition device  18 , a build platform  24 , a directed energy source  32 , and a controller  36 , as described in detail below. The surrogate powder  10  may comprise any number of materials including material that has a high melting point or low melting point, or a combination of both. For example, the surrogate powder  10  may be comprised of casting sand, metal, metal alloys, carbon fiber, silicon, plastic, or other material in powder form. A build powder  14  is also used and may also be comprised of metal, metal alloys, carbon fiber, silicon, plastic, or other material in powder form. The surrogate powder  10  and build powder  14  are stored in separate compartments of a multi-material powder hopper  16 , as illustrated in  FIG. 1 . 
         [0019]    The multi-material powder hopper  16  may contain a plurality of types of powder, including the build powder  14  and surrogate powder  10 . The powder hopper  16  may house the different types of powder in separate containers or compartments, or use walls to keep the powders separate. The powder hopper  16  also comprises a nozzle, or plurality of nozzles, through which powder is selectively supplied. The nozzle or plurality of nozzles can supply powder using solenoids, actuators, or a combination thereof. In one preferred embodiment, the nozzle, or plurality of nozzles, supply powder to a powder deposition device  18  positioned below the nozzle, or plurality of nozzles. 
         [0020]    The actuators  20  may be controlled hydraulically, electrically, or manually. For example, the actuators  20  may comprise electric motors, pumps, circuits, robotic components, mechanical actuation components, hydro-mechanical components, electro-mechanical components, and the like. In some embodiments of the invention, the actuators  20  may comprise a first actuator configured to actuate travel of a portion of the build platform  24 , a second actuator configured to actuate travel of the directed energy source  32  relative to the build platform  24 , and a third actuator configured to actuate travel of at least a portion of the powder deposition device  18  relative to the build platform  24 , as illustrated in  FIG. 2 . In some embodiments of the invention, the first actuator may be configured to actuate travel in directions  42  substantially perpendicular to directions  44 , 46  of travel provided by the second and third actuators, respectively. Furthermore, in some embodiments of the invention, the actuators may be configured to provide travel in two or more directions. Note that the actuators described herein are merely exemplary and do not limit the scope of the invention. For example, the build platform could remain stationary while only the directed energy source  32  and the deposition device  18  are actuated. Alternatively, the directed energy source  32  may remain stationary while the build platform is actuated toward and/or away from the directed energy source  32 . 
         [0021]    In some preferred embodiments of the invention, the deposition device  18  contains multiple selectively openable compartments in which it stores powder supplied by the powder hopper  16 . In another preferred embodiment, the deposition device  18  contains only one powder compartment that stores the type of powder to be immediately deposited. In yet another preferred embodiment, the deposition device  18  is coupled to the hopper  16  so that it deposits the type of powder selectively supplied by the hopper  16 . Furthermore, the powder deposition device  18  may comprise a nozzle, or plurality of nozzles, which may be turned on or off according to commands received by the controller  36 , thereby applying a desired amount and pattern of powder on the build platform  24 , as later described herein. As noted above, the nozzle or plurality of nozzles can supply powder using solenoids, actuators, or a combination thereof. 
         [0022]    The powder deposition device  18  may comprise at least one of the actuators  20  (such as the third actuator) and/or a track  22  upon which the deposition device  18  may move to selectively deposit the powder. The actuators  20  may actuate the movement of the deposition device  18  on the track  22 , moving the position of the deposition device  18  over any region above a build platform  24 . As illustrated in  FIG. 4 , in one embodiment the deposition device  18  may be a multi-material dispensing rake  18 . 
         [0023]    The build platform  24  broadly comprises a horizontal build plate  26  or base plate and at least one vertical wall surrounding the build plate  26 . In one preferred embodiment the build plate  26  sits on top of a rectangular, horizontal elevator plate  28 , where four vertical walls  30  enclose the elevator plate  28 , as illustrated in  FIG. 1 . The elevator plate  28  is vertically movable using actuators  20  (such as the first actuator above), where the elevator plate  28  is vertically movable relative to the four vertical walls  30 . 
         [0024]    The directed energy source  32  may be any kind as is known in the art including but not limited to a laser, electron beam, or other source of directed energy. The energy source  32  may be movably attached to a track  34  such that the energy source  32  can move anywhere in the three-dimensional space above the build platform  24 . In one embodiment, the energy source  32  may be movable within a two-dimensional plane parallel to and above the build platform  24 . The energy source  32  may also be movable such that it can direct its energy in any direction or angle relative to the plane parallel to the build platform  24 . The movement, position, and direction of the energy source  32  may be manually controlled or caused by one or more of the actuators  20  of the types described above (such as the second actuator above). The actuators  20  of the directed energy source  32  may be controlled by the controller  36 . 
         [0025]    The controller  36  may comprise any number of combination of controllers, circuits, integrated circuits, programmable logic devices such as programmable logic controllers (PLC) or motion programmable logic controllers (MPLC), computers, processors, microcontrollers, transmitters, receivers, other electrical and computing devices, and/or residential or external memory for storing data and other information accessed and/or generated by the apparatus  12 . The controller  36  may control operational sequences, power, speed, motion, or movement of the actuators  20  and/or temperature of the directed energy source  32 . 
         [0026]    The controller  36  may be configured to implement any combination of algorithms, subroutines, computer programs, or code corresponding to method steps and functions described herein. The controller  36  and computer programs described herein are merely examples of computer equipment and programs that may be used to implement the present invention and may be replaced with or supplemented with other controllers and computer programs without departing from the scope of the present invention. While certain features are described as residing in the controller  36 , the invention is not so limited, and those features may be implemented elsewhere. For example, databases may be accessed by the controller  36  for retrieving CAD data or other operational data without departing from the scope of the invention. 
         [0027]    The controller  36  may implement the computer programs and/or code segments to perform various method steps described herein. The computer programs may comprise an ordered listing of executable instructions for implementing logical functions in the controller  36 . The computer programs can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, and execute the instructions. In the context of this application, a “computer-readable medium” can be any physical medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be, for example, but not limited to, an electronic, magnetic, optical, electro-magnetic, infrared, or semi-conductor system, apparatus, or device. More specific, although not inclusive, examples of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable, programmable, read-only memory (EPROM or Flash memory), a portable compact disk read-only memory (CDROM), an optical fiber, multi-media card (MMC), reduced-size multi-media card (RS MMC), secure digital (SD) cards such as microSD or miniSD, and a subscriber identity module (SIM) card. 
         [0028]    The residential or external memory may be integral with the controller  36 , stand alone memory, or a combination of both. The memory may include, for example, removable and non removable memory elements such as RAM, ROM, flash, magnetic, optical, USB memory devices, MMC cards, RS MMC cards, SD cards such as microSD or miniSD, SIM cards, and/or other memory elements. As illustrated in  FIG. 1 , electrical conduits  38  and/or communication conduits  38  may also provide electrical power to the actuators  20 , the powder hopper  16 , the deposition device  18 , the nozzles or nozzle solenoids, the build platform  24 , and/or the directed energy source  32 . Additionally or alternatively, the conduits  38  may be configured to provide communication links between the controller  36  and any of the actuators  20 , the powder hopper  16 , the deposition device  18 , the nozzles or nozzle solenoids, the build platform  24 , and the directed energy source  32 . 
         [0029]    In use, the additive manufacturing apparatus  12  may selectively deposit both the build powder  14  and the surrogate powder  10  using the deposition device  18  and selectively melt the build powder  14  using the directed energy source  32  to form a component  40 , layer by layer. Specifically, the depositing and melting steps are repeated one or more times, until the component  40  is complete. The surrogate powder  10  is then removed and may be used again in another additive manufacturing process. The surrogate powder  10  provides structural support to the component  40  during additive manufacturing, helps reduce waste of the build powder  14 , and allows for efficiently recycling of unused powder. 
         [0030]    The flow chart of  FIG. 6  depicts the steps of an exemplary method  100  for additive manufacturing the component  40  using the surrogate powder  10  to provide structural support during formation of the component  40 . In some alternative implementations, the functions noted in the various blocks may occur out of the order depicted in  FIG. 6 . For example, two blocks shown in succession in  FIG. 6  may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order depending upon the functionality involved. Some or all of the steps described below and illustrated in  FIG. 6  may also represent executable code segments stored on the computer-readable medium described above and/or executable by the controller  36 . 
         [0031]    The method  100  may comprise a step of selectively depositing different types of powder on the build platform  24 , as shown in block  102 , including the surrogate powder  10  and build powder  14 . The build powder  14  may be used to build the component  40  and is placed in various regions on the build platform  24 . The surrogate powder  10  may be deposited in regions where the build powder  14  has not been placed. This forms one layer of the component  40  in powder form on the build platform  24 . Additionally or alternatively, this may form one layer of a plurality of components in powder form on the build platform  24  simultaneously, as illustrated in  FIGS. 1-5 . 
         [0032]    The depositing of the different types of powders can be done in any order, including but not limited to placing each type of powder separately or placing both types at once as the deposition device  18  moves in any direction along the plane of the build platform  24 . The build powder  14  and surrogate powder  10  may be deposited in separate regions forming the first layer in powder form. The build powder  14  may be partially or completely surrounded by the surrogate powder  10 , the surrogate powder  10  being useful for lateral support during the additive manufacturing process. Further, the surrogate powder  10  may be deposited in a region partially or completely surrounded by the build powder  14 , the surrogate powder  10  being useful for lateral and vertical support during the additive manufacturing process. The placement of the various regions of the different types of powder in the one layer, or location of these regions&#39; deposition on the build platform  24 , may be according to computer-aided design (CAD) data, or other technical model or drawing, as followed manually by a user or as directed in an automated or semi-automated fashion via control signals provided from the controller  36  to the deposition device  18  and its associated actuators  20  (such as the third actuator). 
         [0033]    Next, the method  100  may include a step of tracing over the build powder  14  with the directed energy source  32 , fusing the first layer of the component  40 , as depicted in block  104 . Specifically, after the first layer of powder has been deposited on the build platform  24 , the directed energy source  32  may be selectively actuated to travel over the build powder regions and/or may be selectively turned on and off, thus melting the build powder  14  only in the regions exclusively containing build powder  14 . For example, a laser beam emitted from the directed energy source  32  may be directed to trace or travel over/through the build powder  14  and its corresponding regions on the build platform  24 . The tracing of the energy source  32  can be done according to CAD data, models, drawings, or other technical resources. The tracing of the energy source  32  over the build powder  14  causes the powder to fuse together, forming one layer of the component  40  in solid form. The energy source  32  may be configured and/or instructed to not trace over the surrogate powder  10 . Additionally or alternatively, the energy source  32  may be configured to output heat that is high enough to fuse the build powder  14  together but not high enough to cause the surrogate powder  10  to fuse with itself, the build powder  14 , or the component  40 . 
         [0034]    Then the method  100  may comprise repeating the steps  102  and  104  one or more times, as depicted in block  106 , until the component  40  is complete, as depicted in block  108 . Specifically, once one layer of the component  40  has been fused, a next layer of powder can be deposited. This is may be accomplished through first lowering the build platform  24  relative to the energy source  32  or deposition device  18 . The lowering may also comprise lowering the base or build plate  26  relative to the walls  30 . Once the lowering has occurred, the process may repeat in that the next layer of powder may be deposited onto a previous layer of the component  40 . This deposition may also include the use of surrogate powder  10  or build powder  14  in the same way as in step  102 . During the fusing step  104 , the build powder  14  fuses together and also fuses to adjacent previous layers of the component  40 . When subsequent layers are fused to the component  40 , the surrogate powder  10  may act as lateral support to layers of the build material adjacent to the surrogate powder  10 . The surrogate powder  10  may also serve as vertical support for layers of build powder  14  that may have been deposited on top of surrogate powder  10  layers during manufacturing of subsequent layers. This process may produce a single component  40 , or a plurality of components  40  manufactured simultaneously. 
         [0035]    Next, the method  100  may include the steps of removing the surrogate powder  10  from the component and/or build platform, as depicted in block  110 , and recycling the removed powder for use in subsequent additive manufacturing, as depicted in block  112 . Because the surrogate powder  10  was not fused to the component  40  or to itself, it is easily removed from any orifices or crevices of the component  40  or components  40 . Further, because the surrogate powder  10  remains in powder form, it can easily be recycled for use in a subsequent additive manufacturing of another component, or set of components. This reduces the waste of build powder  14 , while also increasing the efficiency in recycling used powder in additive manufacturing. 
         [0036]    Although the invention has been described with reference to the one or more embodiments illustrated in the figures, it is understood that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.