Patent Publication Number: US-2021187847-A1

Title: Three-Dimensional Printer Having Platform Section Removable From Actuation in Printer Chassis

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional patent application claims priority to U.S. Provisional Application Ser. No. 62/950,481, Entitled “Three-Dimensional Printer Having Platform section Removable From Actuation in Printer Chassis” by James Francis Smith III, filed on Dec. 19, 2019, incorporated herein by reference under the benefit of U.S.C. 119(e). 
    
    
     FIELD OF THE INVENTION 
     The present disclosure concerns an apparatus and method for a layer-by-layer fabrication of three dimensional (3D) articles utilizing powder materials. More particularly, the present disclosure concerns an optimal build platform design for minimizing a use of powder material. 
     BACKGROUND 
     Three dimensional (3D) printing systems are in rapidly increasing use for purposes such as prototyping and manufacturing. One type of three dimensional printer utilizes a layer-by-layer process to form a three dimensional article of manufacture from powdered materials. Each layer of powdered material is selectively fused at a build plane using an energy beam such as a laser, electron, or particle beam. In other systems the powder is selectively fused by selectively printing or dispensing an absorber onto the powder and then using a blanket exposure of radiation to selectively fuse the powder. One issue with such printers is the high cost of the powder materials. Another issue is with a temperature of a build volume around the article being fabricated. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic diagram of an embodiment of a three-dimensional printing system for manufacturing or fabricating a three-dimensional article. 
         FIG. 2  is an isometric view of an embodiment of a closed three-dimensional printing system. 
         FIG. 3  is an isometric view of an embodiment of a closed three-dimensional printing system with an access door open to allow access to a build chamber. 
         FIG. 4  is an isometric view of a portion of a build platform assembly (hereinafter referred to as a build platform assembly for convenience). 
         FIG. 5  is a top view of an embodiment of a build platform assembly. 
         FIG. 6  is a side isometric view of a build platform assembly positioned above an array of motors. 
         FIG. 7  is an isometric view an array of platen sections mounted in a chassis and coupled to an array of motors. 
         FIG. 8  is a cutaway view of the build platform assembly attached to an array of motors. 
         FIG. 8A  is an upper portion of the cutaway view of  FIG. 8 . 
         FIG. 9  is an isometric view that depicts the chassis  32  supporting a single platen section. 
         FIG. 10  is a side cutaway view of a single platen section. 
         FIG. 11  is a top cutaway view of an array of platen sections with added detail for a central platen section. 
         FIG. 12A  is a cutaway view of a lower portion of a chassis and motor in a disconnected configuration. 
         FIG. 12B  is a cutaway view of a lower portion of a chassis and motor in a connected configuration. 
     
    
    
     SUMMARY 
     In a first aspect of the disclosure, a three-dimensional printer includes a printer housing enclosing a chamber, an array of actuators, a build platform assembly, a powder dispenser, and an energy beam for selectively fusing layers of the powder at the build plane. The array of actuators are mounted above a lower portion of the build chamber. The actuators individually include an upward extending shaft. The build platform assembly includes a chassis, an array of platen sections, and an array of shanks. The array of shanks and the array of platen sections correspond to the array of actuators. The array of platen sections are mounted in the chassis for guided vertical movement and define a corresponding array of top surfaces of a build platen having a selectively configurable geometry. The array of shanks individually have an upper end coupled to one of the array of platen sections and a lower end positioned to receive the upward extending shaft when the lower end of the shank is lowered into the build chamber. The powder dispenser is configured to dispense layers of powder at a build plane above the array of platen sections. The energy beam source is for selectively fusing layers of the powder at the build plane. The array of actuators can include an array of motors for controllably and individually turning the array of shanks. 
     In one implementation, the platen sections individually include an upper wall, a plurality of vertical walls coupled to the upper wall, and define a recess with a lower opening. One or more linear bearings are mounted in the recess. The chassis supports one or more rails or shafts that are received within the one or more linear bearings to vertically guide the platform section. 
     In another implementation, the shank includes a lead screw. The platform recess includes a nut mounted within the recess. The lead screw is received within the nut. Control of the shank by one of the array of actuators (motors) induces vertical movement of the platform section. 
     In yet another implementation, a single platform is removable by lifting the single platform section from the chassis. Lifting the single platform section lifts the lower end of the shank off of the upward extending shaft. 
     In a further implementation, the chassis and the array of platen sections can be removed from the array of upward extending shafts by vertically lifting the chassis. This lifting of the chassis will disconnect a corresponding array of shanks from the upward extending shafts. 
     In a yet further implementation, the shank includes a lead screw and an adapter. The lead screw couples to a nut within the platform section. The adapter has an upper portion for coupling to the lead screw and a lower portion for coupling to the upward extending shaft. 
     In another implementation, the build platform assembly includes a platform housing that laterally surrounds the array of platen sections. The platform housing includes a lower portion that is coupled to the chassis. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic diagram of an embodiment of a three-dimensional printing system  2 . In describing system  2 , mutually orthogonal axes X, Y, and Z can be used. Axes X and Y are lateral axes and generally horizontal. Axis Z is a vertical axis that is generally aligned with a gravitational reference. By “generally” we mean that a measure such as a quantity, a dimensional comparison, or an orientation comparison is by design and within manufacturing tolerances but as such may not be exact. In the description X may be referred to as a first lateral axis and Y may be referred to as a second lateral axis. 
     System  2  has a printer housing  4  for enclosing an internal build chamber  6  within which a three-dimensional article  8  is to be fabricated in a layer-by-layer deposition and fusion of powder material  10 . Within the internal build chamber  6  is a build platform assembly  12  coupled to an array of actuators  14  which are coupled to an actuator driver  15 . The build platform assembly  12  includes an array of platen sections  16  that collectively form a segmented or sectioned build platen  18 . In the diagram of  FIG. 1 , six such platen sections  16  are shown in a linear array, but it is to be understood that the platen sections  16  can be disposed along two lateral dimensions. 
     A gas handling system  20  is coupled to the build chamber  6 . The gas handling system  20  is for managing a pressure and composition of gas inside the build chamber  6 . Gas handling system  20  can include a vacuum pump for removing ambient air or other gas from the build chamber  6 . Gas handling system  20  can also include gas sources for backfilling and pressurizing the build chamber  6  with a non-oxidizing gas such as argon or nitrogen. 
     A powder dispenser  22  is for dispensing and coating layers of powder  10  at a build plane  24  above the build platen  18 . The build plane  24  is defined as an upper surface of a just dispensed layer of powder  10 . In an illustrative embodiment, the powder can include one or more of a polymer, a metal, metal alloy, or a ceramic. Metals can include titanium, stainless steel, or an aluminum alloy to name some examples. A metallic material such as zirconium silicate can be used. 
     A beam system  26  is for generating one or more energy beams  28  and to scan the beam(s) over the build plane  24  to selectively fuse a layer of powder  10 . Energy beam(s)  28  can include one or more of a laser radiation beam, an electron beam, or a particle (other than electrons) beam. In an illustrative embodiment, the beam  28  can include laser radiation with a power level of more than 100 watts, more than 500 watts, about 1000 watts, or more than 1000 watts. For polymer powder systems a radiation beam  28  can have powers that are lower than 100 watts. 
     A controller  30  is controllably coupled to various portions of system  2  including the actuator driver  15 , gas handling system  20 , the powder dispenser  22 , the beam system  26 , and other portions of system  2 . The controller includes a processor coupled to an information storage device which further includes a non-volatile or non-transient information storage device. The non-transient storage device stores software instructions. When executed by the processor, the software instructions control the various portions of system  2 . 
     By executing software instructions, the controller  30  operates the system to fabricate or manufacture the three dimensional article  8  according to the following steps: (1) The array of actuators  14  selectively vertically position the array of platen sections  16 ; (2) The powder dispenser  22  dispenses a layer of powder  10  over the array of platen sections  16 ; (3) The beam system  26  generates and steers beam(s)  28  to selectively fuse the dispensed layer of powder  10  at the build plane  24 ; (4) Steps (1)-(3) are repeated to complete fabrication of the three dimensional article  8  in a layer-by-layer manner. During this process, some of the platen sections  16  are incrementally lowered. Others can be stopped initially or after a certain number of layers to reduce a use of powder  10  required for fabrication. By operating through the actuator driver  15 , the controller  30  can selectively control a height of the platen sections  16  to therefore adjust a topographical geometry of the build platen  18 . In particular, the platen sections  16  that are under the article  8  will move incrementally downward during fabrication and platen sections  16  that are not under article  8  will remain in a top starting position. For some geometries of an article  8 , the platen sections  16  can be vertically staggered. 
     Prior to steps (1)-(4) above, the controller  30  can also operate the gas handling system  20  and a door lock system (not shown) in order to evacuate the build chamber  6  (pump out air) and to backfill the build chamber  6  with an inert gas such as nitrogen or argon. After the steps (1)-(4), the controller can operate the gas handling system  20 , the door lock system, and other portions of system  2  to prepare for unloading part or all of the build platform assembly  12  with a fabricated or manufactured article  8 . 
       FIG. 2  is an isometric view of an embodiment of a three-dimensional printing system  2 . System  2  has outer housing  4  including an access door  5 . The access door  5  can be opened to allow access to the build chamber  6 .  FIG. 3  is an isometric view of the embodiment of the three-dimensional printing system  2  of  FIG. 2  with the access door  5  open. With door  5  open, access to the build chamber  6  enables removal or replacement of the build platform assembly  12 . 
       FIG. 4  is an isometric view of an embodiment of a portion of a build platform assembly  12  (hereinafter referred to as a build platform assembly  12  for convenience) and array of actuators  14 . The build platform assembly  12  includes a chassis  32  that supports the array of platen sections  16 . In the illustrated embodiment, a middle one of the platen sections  16  is shown raised while other platen sections  16  are lowered. Laterally surrounding the platen sections  16  is a platform housing  34 . The chassis  32  includes a lower end  36  with an upward facing surface  38 . A lower end  40  of the platform housing  34  rests upon the upward facing surface  38  and is coupled to the lower end  36  of the chassis  32 . The platen sections  16  individually have a horizontal top surface  42  and a plurality of vertical side surfaces  44  intersecting the top surface  42 . In the illustrated embodiment, the platen section  16  includes six such vertical side surfaces  44 . 
       FIG. 5  depicts a top view of the build platform assembly  12 . In the illustrated embodiment, the platen sections  16  have a top surface  42  defining a hexagonal shape. The hexagonal shape has advantages over squares or rectangles for minimizing use of powder material  10 . However, in alternative embodiments, the top surface can define other shapes such as square, rectangular, triangular or other polygonal shapes. In viewing  FIGS. 3 and 4 , adjacent pairs of platen sections  16  have a vertical gap  46  between them which is filled with a compressible sheet  48 . For a vertical gap  46  there are two opposing and facing vertical side surfaces  44  corresponding to an adjacent pair of platen sections  16 . The compressible sheet  48  is fixedly attached to one of the opposing surfaces  44  and vertically slidingly engages the other opposing and facing surface  44 . 
     In the illustrated embodiment, a platen section  16  has three non-adjacent vertical side surfaces  44  having an attached compressive sheet  48 . The remaining vertical side surfaces  44  of the platen section  16  do not have a compressive sheet  48 , so that all of the vertical gaps  46  can be filled with compressive sheets  48 . Stated another way, a compressive sheet  48  is attached to every other vertical side surface  44  of a platen section  16 . 
     The platform housing  34  has a plurality of inward facing vertical surfaces  50 . Between one of the vertical surfaces  50  of the platform housing  34  and an adjacent platen section  16  is a vertical gap  46 . Between the opposing surfaces  50  and  44  is a compressive sheet  48 . The compressive sheet  48  can either be attached to the vertical surface  50  of the platform housing  34  or to the vertical side surface  44  of the platen section  16  that is facing or in opposition to the vertical surface  50 . In the illustrated embodiment, the compressive sheets  48  are attached to alternating ones of the vertical surfaces  50 . 
     Stated differently for further clarity: The platform housing  34  laterally surrounds the array of platen sections  16 . The platform housing  34  includes a perimeter of inward facing surfaces  50  that face toward the array of platform sections  16 . A plurality of peripheral vertical gaps  46  are defined between the inward facing surfaces  50  and the vertical side surfaces  44  of the platen sections  16 . A peripheral arrangement of the compressible sheets  48  fill the plurality of peripheral vertical gaps  46 . 
     In various embodiments, the compressible sheets  48  are formed from strong, heat-resistant, and compressible materials such as synthetic fibers. Heat resistance is important for metal powder melting systems. The synthetic fibers can be aramid fibers. One example of an aramid fiber is chemically known as Poly-paraphenylene terephthalamide which was branded “Kevlar®” by DuPont (E.I. du Pont de Nemours and Company, Wilmington, Del.). Another aramid fiber is known by a trade name of “Nomex®” also branded by DuPont. Other possible materials could be polyester, wool, carbon fiber, ceramic, and fiberglass. 
     The compressible sheets  48  can have a thickness of about 2 to 10 millimeters, 3 to 7 millimeters, 4 to 6 millimeters or about 5 millimeters. The thickness would depend partly upon compressibility and lateral mechanical tolerances of the vertical gaps  46 . 
     In an illustrative embodiment, the compressible sheets  48  would be formed from a fibrous material such as felt. An example of such a material is known as “DEFENDER™ DURAFIBER BOARD” provided by Albarrie Canada Ltd., located in Barrie, ON, Canada. The material is a felt pad that can be formed from Kevlar® (available in thicknesses from about 1.5 to 10.0 millimeters) and Nomex® (available in thicknesses from about 1.6 to 5.0 millimeters). 
     In the illustrated embodiment, the compressible sheets  48  are attached directly to the vertical side surfaces  44  of the platen sections  16  using fastening means such as screws, rivets, or adhesives. The compressible sheets have a lateral width that is slightly greater than the lateral width of the vertical side surfaces  44  so that three way intersections of the vertical gaps  46  are filled and prevent leakage. In an alternative embodiment, the platen sections  16  can contain spring loaded mechanisms for supporting the sheets  48 . 
       FIG. 6  is an isometric side view of an embodiment of the build platform assembly  12  positioned above an array of actuators or motors  14 . The array of motors  14  are positioned above a lower portion  7  of the build chamber  6  and individually include an upward extending shaft  52 . When the build platform assembly  12  is lowered into the build chamber  6 , the build platform assembly  12  couples to the array of motors  14 , allowing the motors to controllably and selectively raise and lower the platen sections  16  under control of controller  30 . 
       FIG. 7  is an isometric view of an array of platen sections  16  mounted in chassis  32  without the platform housing  34 . Each of the platen sections  16  have a compressible sheet  48  mounted on every other vertical side surface  44 . The platen sections  16  are mounted to the chassis  32  via vertically oriented rails  54 . An array of the motors  14  corresponds to the array of platen sections  16  and raise and lower the platen sections  16  through motor rotation of vertical shanks  56 . 
       FIG. 8  is a cutaway view of the build platform assembly  12 . The platform housing  34  is supported by the chassis  32 . In the illustrated embodiment, the lower end  40  of the platform housing  34  is directly coupled to the chassis  32 . In the illustrated embodiment, the lower end  40  of platform housing  34  also rests on the upward facing surface  38  of the lower end  36  of chassis  32 . 
     Each of the platen sections  16  is coupled to a corresponding motor  14  by a shank  56 . The shank  56  includes a lead screw  62  and an adapter  64 . The adapter  64  couples the lead screw  62  to the upward extending shaft  52  of the motor  14 . 
       FIG. 8A  is an upper portion of the cutaway view of  FIG. 8 . The platen sections  16  are individually hollow and include upper wall  66 , side walls  68 , and define an inner recess  69  and an opening at a lower end. Side walls  68  depend downward from upper walls  66 . Mounted inside each platen section  16  is a nut  70  with inner threads. The lead screw  62  is received within the nut  70 . Inner threads of the nut  70  therefore engage outer threads of the lead screw. Rotation of the lead screw  62  will drive the platen section  16  up or down at a rate that is proportional to an angular rate of rotation and a pitch of threads  63  on the lead screw  62 . In the illustrated embodiment, nut  70  is an anti-backlash lead nut. 
       FIG. 9  is an isometric view that depicts the chassis  32  supporting a single platen section  16  for illustrative purposes. The chassis  32  defines a plurality of vertically extending slots  72  that extend upward from the lower end  36  of the chassis  32 . For the hexagonal-shaped platen sections  16 , the chassis  32  defines six vertically extending slots  72  for each platen section  16 . The vertically extending slots  72  support the rails  54 . 
       FIG. 10  is a side cutaway view of a single platen section  16  that is supported by rails  54  and vertically driven by lead screw  62 . Mounted within the platen section  16  are linear bearings  74  that receive the rails  54 . The linear bearings  74  slidingly engage the rails  54  to guide the platen section  16  vertically. In the illustrated embodiment, six vertical side walls  68  depend downward from the upper wall  66 . A compressible sheet  48  is attached to every other vertical side wall  68 . The compressible sheets  48  can be attached via mechanical fasteners (e.g., screws, rivets, etc.), adhesives, or a thermal compression or welding process. Using small screws has an advantage of making the felt easily replaceable. 
       FIG. 11  is a top cutaway view of an array of platen sections  16  with added detail for a central platen section  16 . In the illustrated embodiment, a single platen section  16  has six linear bearings  74  that are attached within the six side walls  68 . The platen section  16  includes an inner wall  76  within an outer wall  78  is defined by the six side walls  68 . In the illustrated embodiment, the inner  76  and outer  78  walls each define a hexagonal shape. The linear bearings  74  are mounted to an outside surface of the inner wall  76  and are between the inner wall  76  and outer wall  78 . The nut  70  is mounted to an inside surface of the inner wall  76  and is inside the inner wall  76 . Also shown are six rails  54  that slidingly engage the six linear bearings  74 . 
     In another embodiment (not shown) the rails  54  can be metal rods  54  having a solid circular cross-section. In this embodiment, three rods  54  can be used, with a rod for every other side of the hexagonal shape of the outer wall  78 . The linear bearings  74  for engaging the rods  54  would be high temperature linear bearings. A rigid rail  54  and bearing  74  system is important to maintain accurate vertical gaps  46  to have a consistent compression of the compressible sheets  48 . 
       FIGS. 12A and 12B  are cutaway views of a lower portion of the chassis  32  and motor  14  in disconnected ( 12 A) and connected ( 12 B) configurations. In the illustrated embodiment of  FIG. 12A , the adapter  64  defines a lower opening  80  for receiving the upward extending shaft  52 . The connection between the adapter  64  and shaft  52  can vary as can the designs of shaft  52  and opening  80 . For example, some designs may have a detent lock arrangement for coupling shaft  52  and opening  80  together. In one embodiment, the shaft  52  is a splined male shaft (not shown) and the opening is a splined female coupling (not shown). In some embodiments, the actuator  14  may include a sensor (not shown) for verifying proper mechanical coupling. 
     In the illustrative embodiment of  FIG. 12B , the shank  56  is defined as including the lead screw  62  and adapter  64 . In the illustrated embodiment, the adapter  64  is clamped to the lead screw  62  by tightening a screw. Other designs are possible such as a lead screw  62  with a machined lower end that mechanically locks into an adapter  64 . 
     The specific embodiments and applications thereof described above are for illustrative purposes only and do not preclude modifications and variations encompassed by the scope of the following claims.