METHODS AND APPARATUS FOR COMPRESSING MATERIAL DURING ADDITIVE MANUFACTURING

Abstract

An additive manufacturing device and method for delivering a flowable material from a nozzle of a programmable computer numeric control (CNC) machine, and compressing the flowable material with a compression roller. In one embodiment, the device includes a nozzle configured to deposit a flowable material on a surface; and a roller configured to compress the deposited flowable material, wherein the roller comprises: a flat center portion having a constant diameter; and opposed end portions, wherein each end portion extends outwardly from the flat center portion, and wherein a radially outermost surface of each end portion is angled relative a rotational axis of the roller.

Claims

1.-18. (canceled)

19. An additive manufacturing device, the device comprising: an applicator head configured to deposit material on horizontal worktable along a path that includes a non-linear portion; and a roller having an axial length and configured to follow the path to compress the material as the material is deposited on the horizontal worktable; and wherein the roller includes a center portion formed about a midpoint of the axial length of the roller, the center portion coming into contact with the material as the material is being compressed, while end portions on either side of the center portion of the roller overlap a portion of the material without contacting the portion of the material.

20. The device of claim 19, wherein the material is a thermoplastic material.

21. The device of claim 19, wherein the center portion is cylindrical and has a constant diameter.

22. The device of claim 19, wherein the roller is connected to the applicator head via a support structure.

23. The device of claim 22, wherein the support structure extends outwardly with respect to the end portions of the roller and positions the roller on the path behind the material being deposited.

24. The device of claim 19, wherein the applicator head further comprises an opening for depositing the material.

25. The device of claim 24, wherein the opening overlaps the center portion of the roller along a direction parallel to a radial direction defined by the center portion.

26. The device of claim 24, wherein compressing the material includes rolling the roller such that only the center portion contacts and rolls upon an upward-facing surface of the material after it has been deposited through the opening.

27. The device of claim 19, wherein a gap is formed between the end portions of the roller and an upward-facing surface of the material.

28. An additive manufacturing device, the device comprising: a nozzle configured to deposit material along a path that includes a non-linear portion; and a roller configured to follow the path and compress the material as the material is deposited; and wherein the roller has an axial length and includes a center portion formed about a midpoint of the axial length of the roller, the center portion coming into contact with the material as the material is being compressed, while end portions on either side of the center portion of the roller overlap a portion of the material without contacting the portion of the material.

29. The device of claim 28, wherein the material is deposited on a worktable.

30. The device of claim 28, wherein the material is a thermoplastic material.

31. The device of claim 28, wherein the nozzle and the roller are connected to an applicator head.

32. The device of claim 31, wherein the roller is connected to the applicator head via a support structure.

33. The device of claim 32, wherein the support structure extends outwardly with respect to the end portions of the roller and positions the roller on the path behind the material being deposited.

34. The device of claim 28, wherein the nozzle overlaps the center portion of the roller along a direction parallel to a radial direction defined by the center portion.

35. The device of claim 28, wherein compressing the material includes rolling the roller such that the center portion contacts and rolls upon an upward-facing surface of the material after it has been deposited through the nozzle.

36. An additive manufacturing device, the device comprising: an applicator head including a nozzle opening configured to deposit a thermoplastic material on a horizontal worktable along a path that includes a non-linear portion; and a roller connected to the applicator head via a support structure and configured to follow the path; and wherein the roller has an axial length and includes a cylindrical center portion formed about a midpoint of the axial length of the roller, the cylindrical center portion configured to contact the thermoplastic material and cause the thermoplastic material to be compressed, while end portions on either side of the cylindrical center portion of the roller overlap a portion of the thermoplastic material without contacting the portion of the thermoplastic material.

37. The device of claim 36, wherein the support structure extends outwardly with respect to the end portions of the roller and positions the roller on the path behind the thermoplastic material being deposited.

38. The device of claim 36, wherein causing the thermoplastic material to be compressed includes rolling the roller such that the cylindrical center portion contacts and rolls upon an upward-facing surface of the thermoplastic material after it has been deposited through the nozzle opening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary aspects of the present disclosure and together with the description, serve to explain the principles of the disclosure.

[0020] FIG. 1 is a perspective view of an exemplary CNC machine operable pursuant to an additive manufacturing process to form articles, according to an aspect of the present disclosure;

[0021] FIG. 2 is an enlarged perspective view of an exemplary carrier and applicator assembly of the exemplary CNC machine shown in FIG. 1;

[0022] FIG. 3 is an enlarged cross-sectional view of an exemplary applicator head assembly shown in FIG. 2;

[0023] FIG. 4 is an enlarged cross-sectional view of an exemplary deposition head and compression roller assembly, illustrating the slight decompression of a deposited layer, which occurs immediately after the compression roller passes over the deposited bead of molten material;

[0024] FIG. 5a is an enlarged plan view of an exemplary carrier and applicator assembly of the exemplary CNC additive manufacturing machine shown in FIG. 1;

[0025] FIG. 5b is an enlarged plan view of an exemplary bead compression roller, illustrating the different surface features of the roller;

[0026] FIG. 6a is an enlarged cross-sectional view of an exemplary compression roller, with an elliptically tapered outer surface feature, compressing a molten material bead alongside a previously-deposited and compressed layer of material; and

[0027] FIG. 6b is an enlarged cross-sectional perspective view of an exemplary material compression roller, with an elliptically tapered outer surface feature, executing a tool-path directional change.

DETAIL DESCRIPTION OF THE INVENTION

[0028] The present disclosure is drawn to, among other things, methods and apparatus for fabricating multiple components via additive manufacturing techniques, such as, e.g., 3D printing. More particularly, the methods and apparatus described herein comprise a method and apparatus for eliminating, or otherwise substantially reducing damage to the surface of deposited and compressed molten material bead(s) during the stratification process of additive manufacturing by, e.g., providing a compression roller that can flatten and level layers of molten material in the additive manufacturing process, without gouging into, or dragging the previously-deposited material.

[0029] For purposes of brevity, the methods and apparatus described herein will be discussed in connection with fabricating parts from thermoplastic materials. However, those of ordinary skill in the art will readily recognize that the disclosed apparatus and methods may be used with any flowable material suitable for additive manufacturing, such as, e.g., 3D printing.

[0030] In one aspect, the present disclosure is directed to an extruder-based 3D printing head including a compression roller having a shape that facilitates compressing a bead of flowable material (e.g., a thermoplastic material) by eliminating distortion of the layered and compressed surface. With reference now to FIG. 1 of the drawings, there is illustrated a programmable computer numeric control (CNC) machine 1 embodying aspects of the present disclosure. A controller (not shown) may be operatively connected to machine 1 for displacing an application nozzle along a longitudinal line of travel or x-axis, a transverse line of travel or a y-axis, and a vertical line of travel or z-axis, in accordance with a program inputted or loaded into the controller for performing an additive manufacturing process to replicate a desired component. CNC machine 1 may be configured to print or otherwise build 3D parts from digital representations of the 3D parts (e.g., AMF and STL format files) programmed into the controller. For example, in an extrusion-based additive manufacturing system, a 3D part may be printed from a digital representation of the 3D part in a layer-by-layer manner by extruding a flowable material. The flowable material may be extruded through an extrusion tip carried by a print head of the system, and is deposited as a sequence of beads or layers on a substrate in an x-y plane. The extruded flowable material may fuse to previously deposited material, and may solidify upon a drop in temperature. The position of the print head relative to the substrate is then incrementally advanced along a z-axis (perpendicular to the x-y plane), and the process is then repeated to form a 3D part resembling the digital representation.

[0031] Machine 1 includes a bed 20 provided with a pair of transversely spaced side walls 21 and 22, a gantry 23 supported on side walls 21 and 22, carriage 24 mounted on gantry 23, a carrier 25 mounted on carriage 24, an extruder 61, and an applicator assembly 43 mounted on carrier 25. Supported on bed 20 between side walls 21 and 22 is a worktable 27 provided with a support surface disposed in an x-y plane, which may be fixed or displaceable along an x-axis. In the displaceable version, the worktable may be displaceable along a set of rails mounted on the bed 20 by means of servomotors and rails 28 and 29 mounted on the bed 20 and operatively connected to the worktable 27. Gantry 23 is disposed along a y-axis, supported at the ends thereof on end walls 21 and 22, either fixedly or displaceably along an x-axis on a set of guide rails 28 and 29 provided on the upper ends of side walls 21 and 22. In the displaceable version, the gantry 23 may be displaceable by a set of servomotors mounted on the gantry 23 and operatively connected to tracks provided on the side walls 21 and 22 of the bed 20. Carriage 24 is supported on gantry 23 and is provided with a support member 30 mounted on and displaceable along one or more guide rails 31, 32 and 33 provided on the gantry 23. Carriage 24 may be displaceable along a y-axis on one or more guide rails 31, 32 and 33 by a servomotor mounted on the gantry 23 and operatively connected to support member 30. Carrier 25 is mounted on a set of spaced, vertically disposed guide rails 34 and 35 supported on the carriage 24 for displacement of the carrier 25 relative to the carriage 24 along a z-axis. Carrier 25 may be displaceable along the z-axis by a servomotor mounted on the carriage 24 and operatively connected to the carrier 25.

[0032] As best shown in FIG. 2, fixedly mount to carrier 25 is a positive displacement gear pump 74, driven by a servomotor 75, through a gearbox 76. Gear pump 74 receives molten plastic from extruder 61 shown in FIG. 1. As shown in FIG. 2, a tangentially compensated bead-shaping compression roller 59, rotatably mounted in carrier bracket 47, provides a means for flattening and leveling a bead of flowable material (e.g., a thermoplastic material), as also shown in FIG. 3. Carrier bracket 47 may be adapted to be rotationally displaced by means of a servomotor 60, as shown in FIG. 2), through a sprocket 56 and drive-chain 65 arrangement.

[0033] With continuing reference to FIG. 3, applicator head 43 may include a housing 46 with a roller bearing 49 mounted therein. Carrier bracket 47 is fixedly mounted to an adaptor sleeve 50, journaled in bearing 49. As best shown in FIGS. 2-3, a bead of a flowable material (e.g., a thermoplastic material) under pressure from a source (e.g., one or more extruder 61 and an associated polymer or gear pump) disposed on carrier 25, to applicator head 43, may be fixedly (or removably) connected to, and in communication with nozzle 51. In use, the flowable material 53 (e.g., melted thermoplastic) may be heated sufficiently to form a molten bead thereof, delivered through applicator nozzle 51, to form uniform, smooth multiple rows of deposited material free of trapped air on to surface 27. Such beads of molten material may be flattened, leveled, and/or fused to adjoining layers by bead-shaping compression roller 59, to form an article. Even though compression roller 59 is depicted as being integral with application head 43, compression roller 59 may be separate and discrete from applicator head 43.

[0034] In some embodiments, the deposited material 53 may be provided with a suitable reinforcing material, such as, e.g., fibers that facilitate and enhance the fusion of adjacent layers of extruded flowable material 53.

[0035] In some embodiments, machine 1 may include a velocimetry assembly (or multiple velocimetry assemblies) configured to determine flow rates (e.g., velocities and/or volumetric flow rates) of material 53 being delivered from applicator head 43. The velocimetry assembly preferably transmits signals relating to the determined flow rates to the aforementioned controller coupled to machine 1, which may then utilize the received information to compensate for variations in the material flow rates.

[0036] In the course of fabricating a component, pursuant to the methods described herein, the control system of the machine 1, in executing the inputted program, may control several servomotors described above to displace the gantry 23 along the x-axis, displace the carriage 24 along the y-axis, displace the carrier 25 along a z-axis, and rotates bracket 47 about a z-axis while compression roller 59 forms uniform, smooth rows of deposited material 52 free of trapped air to create an article.

[0037] With reference now to FIG. 4, there is illustrated a cross-sectional schematic representation of a flowable material (e.g., melted thermoplastic) extrusion and application system. During an additive manufacturing process, there is a slight decompression of the deposited layer 53, which occurs immediately after the compression roller 59 passes over the bead of flowable material (e.g., melted thermoplastic material). Such a decompression results in the surface of the final flattened layer rising up, and remaining slightly higher than the bottom of the compression roller 59. This decompression is best shown FIG. 4, where distance A illustrates a difference in height between the bottom apex of the compression roller 59, and the top of the decompressed material bead 53. Owing to this decompression, when the applicator head 43 rotates to execute a change in tool-path direction, the edges, as well as the outer regions, of the roller 59 tend to engage the surface of the final flattened layer, since it is slightly higher than the bottom apex of the roller, resulting in the roller gouging and/or dragging the deposited material during the transition.

[0038] With reference now to FIGS. 5a and 5b, the surface-contour of compression roller 59 can be seen in both enlarged plan views. Compression roller 59 comprises a flat center portion C for engaging and flattening the deposited bead, with the outer extremities of said roller gradually tapering to the ends in a slight elliptical curve, as shown as portions A and B in FIG. 5b. The flat surface C of roller 59 provides smooth compression and bonding of the deposited material layer, while the gradually-curved outer surfaces facilitates destruction-free tracking along curved portions of the deposited layer, as well as during directional changes in the tool path.

[0039] In FIG. 5b, the surface features are annotated as A, B, and C for descriptive purpose. A and B show the elliptically-tapered outer segments of the roller, while C shows the flat middle feature of the roller. The gradual outer taper of roller 59 prevents the roller 59 from gouging and dragging molten thermoplastic material from the surface of the flattened layer when the roller is advanced in a non-linear direction (e.g., when the roller turns a corner) during the stratification process, as well as when depositing and compressing a bead of flowable material (e.g., melted thermoplastic) adjacent to a previously-deposited adjoining layer, which may still be molten. By comparison, a completely cylindrical compression roller (e.g., a roller without the tapered segments A and B depicted in FIG. 5b) would gouge and drag the material while navigating around corners and curves, as the entire roller surface would be engaged with the slightly-decompressed and raised material surface. Compression roller 59 smooths and bonds the layer with the flat portion of the roller, and the gradual tapering of the outer surfaces allows it to negotiate around the corners without producing objectionable surface imperfections.

[0040] FIG. 6a, which depicts a cut-away end view of deposited strata, exemplifies the bead compression process, using the described compression roller 59 during the deposition of a bead of flowable material (e.g., melted thermoplastic) adjacent to a previously deposited and compressed bead. Tapered end 63 of the compression roller 59 does not substantially engage a previously deposited layer 72, and therefore has minimal or no effect on the surface of layer 72. In some embodiments, the tapered end 63 of the compression roller 59 may be tapered at both ends, as shown in FIG. 6a. In other embodiments, compression roller 59 may include only a single tapered end 63. In some embodiments, the tapered end 63 may be angled “a” approximately 1 to 15 degrees relative to the surface of the center, flat portion of roller 59. In some other embodiments, tapered end 63 may include a non-linear relief (e.g., the relief is not a straight line, but a taper curving away from the radially outermost surface of compression roller 59).

[0041] With reference now to FIG. 6b, which is a cut-away view of strata deposited in two directions, there is shown, an exemplary view of the compression roller 59, executing a change of direction in the bead deposition process. The tapered portion 63 of roller 59 does not engage the material on the adjoining side of the article, because roller 59 is slightly tapered to prevent any substantial contact with the surface of that side of the deposited strata of previously deposited layers. After deposition of a flowable material (e.g., melted thermoplastic) on surface 27, as shown in FIG. 3, and while the topmost layer of deposited strata 72, as shown in FIG. 6a, is cooling (e.g., the melted material has not completely solidified), compression roller 59 is used to flatten deposited strata 72 to create a uniform deposited layer. In some examples, however, compression roller 59 must be used to flatten deposited strata 72 in a non-linear manner (e.g., when navigating a corner or curve). In such instances, compression roller 59 is used to compress the unsolidified top-most layer of deposited strata 72, while navigating around the corner or curve, such that any flowable material of the top most layer of deposited strata 72 is not gouged and/or dragged. Moreover, when roller 59 navigates a corner or curve, the roller 59 would be engaged with the slightly-decompressed and raised material surface, as previously described above.

[0042] While principles of the present disclosure are described herein with reference to illustrative embodiments for particular applications, it should be understood that the disclosure is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, embodiments, and substitution of equivalents all fall within the scope of the embodiments described herein. Accordingly, the inventions described herein are not to be considered as limited by the foregoing description.