Abstract:
Disclosed is a 3D printer with a build platform configured to quickly and easily release a build object with no damage to the object. The build platform comprises a rigid frame; an adhesion surface configured to detachably attach to the upper side of the rigid frame; and rack assembly configured to attach to the bottom side of the rigid frame. The rigid frame includes a substantially planar plate of steel, while the adhesion surface comprises a flexible sheet material with an inherent concave curvature with the center biased toward the steel plate. Sets of clips and tabs integral to either the rigid frame or adhesion surface may be employed to releasable lock the frame and adhesion surface together. Sets of protrusions and dimples integral to either the rigid frame or adhesion surface may be employed to releasable lock the frame and adhesion surface together. To release a printed object, the user need only detach the adhesion surface from the rigid frame, and then twist the adhesion surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/187,099 filed Jun. 30, 2015, titled “3D printer with removeable release layer,” which is hereby incorporated by reference herein for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a 3D printer with a detachable build platform. In particular, the invention relates to a build platform configured to easily release objects built with the 3D printer. 
       BACKGROUND 
       [0003]    One type of 3D printer extrudes thermoplastic onto a build platform as the extruder and build platform move laterally relative to one another. When the object being built is completed, the user must remove the object from the build platform by pulling at the object. If the object is delicate, or if the object is stuck to the build platform, the object may be damaged when the user attempts to remove the object from the build platform. There is therefore a need for a 3D printer in which the object can easily be release from the build platform without any damage to the object. 
       SUMMARY 
       [0004]    The invention in the preferred embodiment features a build platform for a 3D printer. The platform comprises a rigid frame; an adhesion surface configured to detachably attach to the top side of the rigid frame; and rack assembly configured to attach to the bottom side of the rigid frame. The rigid frame includes a substantially planar plate of steel, while the adhesion surface comprises a flexible sheet material with an inherent concave curvature with the center biased toward the steel plate. Sets of clips and tabs integral to either the rigid frame or adhesion surface may be employed to detachably attach the frame and adhesion surface together. Sets of protrusions and dimples integral to either the rigid frame or adhesion surface may be employed to detachably attach the frame and adhesion surface together. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, and in which: 
           [0006]      FIG. 1  is a perspective view of an extruder-based 3D printer with moveable build platform, in accordance with a first embodiment of the present invention; 
           [0007]      FIG. 2  is a perspective view of the top side of a positioning mechanism with a moveable build platform, in accordance with a first embodiment of the present invention; 
           [0008]      FIG. 3  is a perspective view of the underside of the moveable build platform, in accordance with a first embodiment of the present invention; 
           [0009]      FIG. 4  is an exploded view of the moveable build platform, in accordance with a first embodiment of the present invention; 
           [0010]      FIG. 5  is a bottom view of the detachable adhesion surface, in accordance with a first embodiment of the present invention; 
           [0011]      FIG. 6  is a side view of the detachable adhesion surface, in accordance with a first embodiment of the present invention; and 
           [0012]      FIG. 7  is a side view of the detachable adhesion surface, in accordance with a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    The present invention pertains to a 3D printer with a build platform and extruder that move relative to one another in three dimensions. The printer includes a positioning mechanism configured to move the build platform horizontally in two directions and move the extruder vertically in response to a computer, processor, or other type of controller. A layer of object is printed or otherwise constructed by shifting the platform in the horizontal plane while simultaneously extruding thermoplastic material at a precise location onto the object being constructed. The build platform is shifted horizontally along the x-axis and/or y-axis to precisely position the object under a nozzle that extrudes the thermoplastic material. After a layer is printed, the nozzle and build platform are moved apart a small distance and the process of printing a layer repeated. 
         [0014]    Illustrated in  FIG. 1  is a preferred embodiment of a 3D printer  100  a thermoplastic extruder assembly  150 , a moveable build platform or build platform  110 , and a positioning mechanism. The positioning mechanism includes a frame  160 , at least one actuator (not shown) for moving the extruder assembly vertically, at least two actuators (not shown) for moving the build platform laterally, and position controller (not shown) for energizing the actuators. The build platform  110  moves relative to the frame  160  in response to rotation of the pinion wires  120  and  140 . The extruder assembly  150  includes a material feeder (not shown) for inputting raw thermoplastic material, a heating element (not shown) for melting the thermoplastic material, and an extruder head  152  for dispensing the thermoplastic material onto an object being constructed on the build platform  110 . The position controller moves the platform in two dimensions as thermoplastic is dispensed from the extruder head to form a layer in the form of a 2D cross-section of the object, in the preferred embodiment. Successive layers are built by raising the extruder assembly relative to the build platform  110  using stanchions or arms  154 . 
         [0015]    Illustrated in  FIG. 2  is a perspective view of the upper side of the build platform  110  and frame  160 . The build platform  110  includes a planar surface on the top and plurality of gear racks  130 A,  150 A underneath. The gear racks  130 A,  150 A each comprise a plurality of teeth arrayed in rows across the length and width of the build platform. The gear racks  130 A and  150 A, in turn, engage pinion wires  120  and  140 , respectively, which carry the weight of the build platform as well as move the build platform laterally. The first gear rack  130 A and pinion wire  120  serve as a first rack and pinion for moving the platform in the x-direction. The second gear rack  150 A and pinion wire  140  serve as a second rack and pinion for moving the platform in the y-direction. The first rack  130 A and pinion wire  120  operate substantially orthogonal to the second rack  150 A and pinion wire  140 . The pinion wires  120 ,  140  are independently driven by motors as disclosed in U.S. patent application Ser. No. 14/508,808 filed Oct. 7, 2014, which is hereby incorporated by reference herein. 
         [0016]    The underside of the build platform  110  and pinion wires are illustrated in  FIG. 3 . The first pinion wire  120  engages a first set of gear racks  130 A,  130 B. Similarly, the second pinion wire  140  engages a second set of gear racks  150 A,  150 B. To move to the upper right, for example, the first pinion wire  120  is rotated clockwise which drives the first set of gear racks  130 A,  130 B. While moving to the right, the second set of gear racks  150 A,  150 B are configured to slide along the pinion wire  140  in a direction parallel to the pinion wire  140 . Similarly, to move the build platform  110  to the upper left, the second pinion wired  140  is rotated counter-clockwise which also causes the first set of gear racks  130 A,  130 B to slide over and against the first pinion wire  120 . Because the two pinion wires are orthogonal, the build platform  110  can be driven in any direction in the horizontal plane by turning the two pinion wires at the appropriate rates. 
         [0017]      FIG. 3  also illustrates an alignment rack, in accordance with one embodiment of the present invention. The alignment rack  300  is configured to ensure that the build platform  110  is properly aligned with the gear racks  130 A,  130 B,  150 A,  150 B when the user sets the build platform onto the pinion wires  120 ,  140 . The build platform is properly aligned when the pinion wires  120 ,  140  are fully seated into the proper teeth of their respective gear racks. That is, the first pinion wire  120  seats with the nth tooth of both gear racks  130 A and  130 B, and the second pinon wire  140  seats with the mth tooth of both gear racks  150 A and  150 B. 
         [0018]      FIG. 4  is an exploded view of the moveable build platform, which consists of a rigid frame, a rack assembly, fasteners, and a detachable adhesion surface. In the preferred embodiment, the rigid frame  420  comprises at least one a metal plate or other planar member to which other structures can be securely attached. In the preferred embodiment, the metal plate is two millimeters thick and uniformly planar to within approximately 100 microns across the upper side of the plate. One skilled in the art will appreciate that the level of uniformity may vary depending on the application. In the preferred embodiment, the rigid frame comprises steel due to the fact that it is stiff and exhibits good thermal conductivity. The edges of the steel plate  420  include a pattern configured to attach to the adhesion surface  410 . In the preferred embodiment, the adhesion surface includes clips  412  that drop through recesses  422  and slide under tabs  424  to secure the steel plate and adhesion surface together by means of a friction fit. 
         [0019]    The steel plate  420  further includes a locking feature configured secure and level the adhesion surface over the steel plate. The locking feature includes a plurality of protrusions  428  on the top surface of the steel plate that coincide with dimples in the underside of the adhesion surface. The friction fit between the protrusions and the dimples prevents slippage of the adhesion surface and provides the user a tactile experience when locking the two pieces together. 
         [0020]    The rack assembly  430  is configured to mount to the underside of the steel plate  420 . In the preferred embodiment, the rack assembly includes apertures  432  configured to receive four threaded studs (not shown) that are pressed into holes  426 , pass through apertures  432 , and receive nuts  440 . As described above, the rack assembly includes gear racks  130 A and  130 B (not shown) as well as racks  150 A and  150 B (not shown). A plurality of legs  434  are also configured to extend below the racks  130 A,  150  where they protect the racks and provide a stop to limit the lateral range of the build platform. 
         [0021]    The adhesion surface  410 , the bottom side of which is shown in  FIG. 5  and side view in  FIG. 6 , is configured to receive molten thermoplastic directly from the extruder head  152 . 
         [0022]    The particular material from which the adhesion surface is made is selected to provide sufficient adhesion to hold the object being constructed to the build platform during product, in the preferred embodiment, the adhesion surface includes a polycarbonate-acrylonitrile butadiene styrene (PC/ABS) blend for use with PLA (polylactic acid) filaments. 
         [0023]    The adhesion surface is, in turn, configured to clip to the steel plate by means of flanges  412  that capture tabs  424 . As described above, the three protrusions  428  in the steel are configured to seat into dimples  418  to effectively lock the assembly together by means of a friction fit. 
         [0024]    As illustrated in side view in  FIG. 6 , the adhesion surface in some embodiments includes a concave curvature to bias the center of the adhesion surface toward the steel plate. The concave curvature is molded into the adhesion surface at time of manufacture. When clipped to the steel plate, the adhesion surface is forced to flatten out and take the shape of the steel plate, thereby enabling the steel plate to control the flatness of the upper side of the adhesion surface. 
         [0025]    When the 3D print operation is complete, the user has two options to remove the print from the adhesion surface. First, the user may simply grab the 3D object and pry it off the adhesion surface. Second, the user may slide the adhesion surface off of the steel plate and twist the opposing ends of the adhesion surface in opposite directions, as shown in  FIG. 7 . The twisting motion releases the 3D object with little effort and no damage to the part. In the preferred embodiment, the adhesion surface is configured to twist approximately three degrees per lineal length of the tray in response to a torque of about 15 to 20 lbf-in (pound force inches). 
         [0026]    In some embodiments, the upper side of the adhesion surface  410  is textured to enhance the adhesion between the extruded material and the surface. A surface textured with peaks and valleys, for example, provides a larger surface than a flat, planar surface. In some additional embodiments, the adhesion surface includes a LEGO pattern of studs, tubes, and/or bars that serve as a mold for the bottom surface of the object being constructed, thus enabling the object to be mounted to LEGO blocks upon completion. 
         [0027]    One or more embodiments of the present invention may be implemented with one or more computer readable media, wherein each medium may be configured to include thereon data or computer executable instructions for manipulating data. The computer executable instructions include data structures, objects, programs, routines, or other program modules that may be accessed by a processing system, such as one associated with a general-purpose computer or processor capable of performing various different functions or one associated with a special-purpose computer capable of performing a limited number of functions. Computer executable instructions cause the processing system to perform a particular function or group of functions and are examples of program code means for implementing steps for methods disclosed herein. Furthermore, a particular sequence of the executable instructions provides an example of corresponding acts that may be used to implement such steps. Examples of computer readable media include random-access memory (“RAM”), read-only memory (“ROM”), programmable read-only memory (“PROM”), erasable programmable read-only memory (“EPROM”), electrically erasable programmable read-only memory (“EEPROM”), compact disk read-only memory (“CD-ROM”), or any other device or component that is capable of providing data or executable instructions that may be accessed by a processing system. Examples of mass storage devices incorporating computer readable media include hard disk drives, magnetic disk drives, tape drives, optical disk drives, and solid state memory chips, for example. The term processor as used herein refers to a number of processing devices including personal computing devices, servers, general purpose computers, special purpose computers, application-specific integrated circuit (ASIC), and digital/analog circuits with discrete components, for example. 
         [0028]    Although the description above contains many specifications, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. 
         [0029]    Therefore, the invention has been disclosed by way of example and not limitation, and reference should be made to the following claims to determine the scope of the present invention.