Patent Publication Number: US-10780612-B2

Title: Method for generating and dispensing a powdered release agent

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a divisional of, and claims priority to, U.S. patent application Ser. No. 14/960,647, filed 7 Dec. 2015, and entitled, “Apparatus for Generating and Dispensing a Powdered Release Agent”, now U.S. Pat. No. 10,105,876, the entire content of which is incorporated herein by reference as if included at length. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     This invention was made with government support under Contract No. DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in the invention. 
    
    
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     None. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC OR AS A TEXT FILE VIA THE OFFICE ELECTRONIC FILING SYSTEM (EFS-WEB) 
     None. 
     STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT INVENTOR 
     None. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to additive manufacturing and more specifically to machines and methods for generating and dispensing a powdered release agent material between layers of a part as it is being built. The powdered release agent significantly improves the process of separating supports from a part after it is built. 
     2. Description of the Related Art 
     Additive manufacturing is a process used to efficiently manufacture three-dimensional parts layer-by-layer. Unlike subtractive technologies that require additional time and energy to remove excess material from oversized raw stock, additive manufacturing deposits material only where it is needed, making very efficient use of time, energy and raw materials. Additive manufacturing may be accomplished using polymers, alloys, resins or other materials that transition from a liquid or powder to a solid. 
     The Manufacturing Demonstration Facility (MDF) at Oak Ridge National Laboratory (ORNL) pioneered the Big Area Additive Manufacturing (BAAM) technology, which is based on extruding thermoplastic pellets through a screw extruder in very large-scale. In order to construct features such as cantilevered beams, overhangs, and arches, sacrificial supports must be built to counteract gravity. Once the part is complete, the sacrificial supports are removed using various mechanical and/or chemical means. The removal of support structures is time-consuming and the part can be unintentionally damaged. The removal of supports becomes increasingly more difficult when large-scale parts are built due to the size and weight of the parts and the support structure. 
     Improvements are needed to advance additive manufacturing beyond the current state of the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Disclosed are several examples of additive manufacturing machines and methods for generating and dispensing a powdered release agent material between layers of a part made using additive manufacturing. 
     The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed can be gained by taking the entire specification, drawings, claims and abstract as a whole. 
     Provided is an apparatus for generating and dispensing a powdered release agent material on a surface of a part that is being built with an additive manufacturing machine. A housing includes an attachment for fastening the apparatus to the additive manufacturing machine. A magazine affixed to the housing feeds a solid body of release agent material into a grinding chamber defined by the housing. A grinder disposed inside of the grinding chamber powderizes the release agent material. Finally, a nozzle dispenses the powdered release agent material on a surface of the part. 
     Provided is a method for generating and dispensing a powdered release agent material on a surface of a part that is being built with an additive manufacturing machine. First, an apparatus as described above is provided. Second, at least one solid body of release agent material is loaded into the magazine. Third, a solid body of release agent material is fed from the magazine into the grinding chamber. Fourth, the apparatus is positioned with the additive manufacturing machine so that the nozzle is adjacent to the surface to receive powdered release agent. Fifth, the grinder is rotated to generate a powdered release agent. Sixth, the powder is dispensed from the nozzle onto the surface of the part. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The apparatuses, methods and articles may be better understood with reference to the following drawings and description. Non-limiting and non-exhaustive descriptions are described with reference to the following drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating principles. In the figures, like referenced numerals may refer to like parts throughout the different figures unless otherwise specified. 
         FIG. 1  is an isometric view of an exemplary apparatus with portions of an additive manufacturing machine illustrated with phantom lines. 
         FIG. 2  is an exploded view of the exemplary apparatus of  FIG. 1  with the attachment removed for clarity. 
         FIG. 3  is a top view of an exemplary magazine. 
         FIG. 4  is a front view of the exemplary magazine of  FIG. 3 . 
         FIG. 5  is a side view of another exemplary magazine. 
         FIG. 6  is a side view of an exemplary grinder assembly. 
         FIG. 7  is a sectional view of the exemplary grinder assembly of  FIG. 6  taken along line  7 - 7 . 
         FIG. 8  is a side view of the exemplary grinder assembly of  FIG. 6 . 
         FIG. 9  is a sectional view of the exemplary grinder assembly of  FIG. 8  taken along line  9 - 9 . 
         FIG. 10  is a flow chart illustrating exemplary method steps for generating and dispensing a powdered release agent material. 
         FIG. 11  is a sectional schematic representation of a 3D article of manufacture. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference first to  FIGS. 1-2 , the major assemblies of an apparatus  20  for generating and dispensing a powdered release agent will now be described. An attachment  22  mounts the apparatus  20  to a component of the additive manufacturing machine  24  that provides up to six axes of controlled movements. For example, the apparatus  20  may be mounted to a nozzle assembly of the additive manufacturing machine  24  and its functions managed by a common controller. In another example, the apparatus  20  is mounted to a dedicated arm of the additive manufacturing machine  24  that is managed by a common controller. In other examples, the apparatus  20  is separately managed by a dedicated controller. A magazine  26  stores one or more solid bodies  28  of release agent material which, in turn, are powderized insitu in a grinder assembly  30 . Other features of the major assemblies will now be described in greater detail. 
     With reference now to  FIGS. 3-4 , an exemplary magazine  26  with horizontal stacking will now be described. A frame  32  defines a track  34  for accepting a slider  36  and one or more solid bodies  28  of release agent material. In this example, the solid bodies  28  are cylindrical shaped, but other shapes, such as square or hexagonal, for example, may be used. The slider  36  contacts the last solid body  28  and loads the first solid body  28  against an escapement plunger  38 . When a solid body  28  is requested by the controller, the escapement plunger  38  retracts via one or more pneumatic cylinders  40  ( FIG. 2 ) and constant force springs  42  pull the slider  36  forward, loading the next available solid body  28  in front of the retracted escapement plunger  38 . The escapement plunger  38  then extends into the track  34  via the one or more cylinders  40 , feeding the loaded solid body  28  and blocking the remaining solid bodies  28 . Miniature pneumatic cylinders PN sdr-05-12 from Clippard Instrument Laboratory, Inc., were used for the cylinders  40  for example. A handle  44  affixed to the slider  36  allows it to be manually retracted for loading additional solid bodies  28  into the track  34 . The escapement plunger  38  function is managed by the controller, automatically with a switch or manually with a switch. 
     With reference now to  FIG. 5 , an exemplary magazine  26  with vertical stacking will be described. In this embodiment, the slider  36 , constant force springs  42  and handle  44  are not necessary. A frame  32  defining a converging track  34  allows the solid bodies  28  to be automatically fed by gravity against the escapement plunger  38 . Upon command, the escapement plunger  38  retracts to load the next available solid body  28  and then extends into the track  34  to feed the loaded solid body  28  from the magazine  26 . A transparent frame  32  or windows in the frame  32  allow the inventory of solid bodies  28  to be visually monitored. 
     Referring now to  FIGS. 6-9  further details of an exemplary grinder assembly  30  will be described. A housing  46  defines a grinding chamber  48 , which accepts a rotatable grinder  50 . A tight tolerance between the housing  46  and the grinder  50  must be maintained to prevent small pieces of release agent material from becoming wedged between the housing  46  and the grinder  50 . An inlet  52  receives a solid body  28  of release material fed from the magazine  26  and positions it at the center and perpendicular to the grinder  50 . The inlet  52  may be open to the top or a side of the housing  46 , depending on the positioning of the magazine  26 . The grinder  50  includes an abrasive surface  54 , having protruding teeth, knife edges, burrs and the like. A sharp-tooth grinding bit or wheel, PN 4257A831 from McMaster Carr Supply company, was used for the grinder  50  for example. A variable speed electric motor  56  ( FIGS. 1-2 ) turns the grinder  50  directly or through a drive  58  such as a toothed belt and pulleys as shown. Please note that the direction of the grinder  50  is counter clockwise as shown in  FIG. 7  to effectively direct the powdered  60  release agent to an outlet nozzle  62 . The outlet nozzle  62  may be straight or curved and includes an orifice  64  that may be sized and shaped to control the pattern of powdered  60  release agent dispensed. The volume of powdered  60  release agent is controlled by the speed of the motor  56  with a greater volume of powder released at the rotational speed increases. A device  66  for applying a load, such as a pneumatic cylinder ( FIGS. 1-2 ), drives the solid body  28  into the grinder  50 . A miniature pneumatic cylinder, PN sdr-05-4 from Clippard Instrument Laboratory, Inc. was used as the loading device  66  for example. An adjustable brush  68  contacts the abrasive surface  54  and dislodges any accumulated powdered  60  release agent as the grinder  50  turns. 
     The powdered  60  release agent impedes adhesion and cross linking between adjacent layers of a base material  70  of an article  72  made by additive manufacturing. By generating the powdered  60  release agent from a solid body  28 , insitu, the powder  60  can be dispensed in the exact location, in the exact amount and at the exact time needed. Since no powder  60  is actually loaded or stored in the apparatus  20 , the potential for spillage, waste, inconsistent dispensing, inadvertent dispensing, and clumping due to humidity is eliminated. The powder  60  grain size is consistent and depends on the grinder  50  chosen. The preferred release agent material is Chalk, which is a form of Calcium Carbonate (CaCO 3 ), although Talc, Limestone, Cornstarch, Corn meal, Graphite, Gypsum, or other solid release agents may be used. The preferred size of the solid bodies  28  is approximately 0.35 of an inch (9 millimeters) in diameter and 3.15 inches (80 millimeters) long. 
     A method  100  for dispensing a powdered release agent is schematically shown in  FIG. 10 . In step  101 , an apparatus as described above is provided. In step  102 , a solid body  28  is loaded into a magazine  26 . In step  103 , the solid body  28  is fed into a grinding chamber  48 . In step  104 , the apparatus  20  is positioned over the surface of the part. In step  105 , the grinder  50  is rotated. In step  106 , the powdered  60  release agent is dispensed from the outlet nozzle  62 . In some examples, steps  104 - 106  are performed simultaneously. 
       FIG. 11  illustrates an exemplary part, build or article of manufacture  72  that is manufactured by additive manufacturing while using the disclosed apparatus  20  and method  100 . A base material  70 , such as polymer plastic for example, is deposited by a nozzle in layers on a build platform  74 . Features such as cantilevered beams, arches, holes and the like require a support structure  76  to counteract the effect of gravity. The support structure  76  may be made of the base material  70  or another material. After the support structure  76  is complete and before a subsequent and/or an adjacent layer of base material  70  is deposited by the nozzle, the powdered  60  release agent material is dispensed by the apparatus  20 . With the addition of the powdered  60  release agent, the support structure  76  is easily separated from the base material  70  when the part is complete, saving time and preventing the part  72  from sustaining unintentional damage. Note that the powdered  60  release agent material may also be dispensed on portions of the platform  74  to simplify the removal of the part  72 . 
     While this disclosure describes and enables several examples of apparatuses and methods for generating and dispensing a powdered release agent, other examples and applications are also contemplated. Accordingly, the invention is intended to embrace those alternatives, modifications, equivalents, and variations as fall within the broad scope of the appended claims. The technology disclosed and claimed herein may be available for licensing in specific fields of use by the assignee of record.