CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 63/231 ,879 filed on August 11 , 2021 .

TECHNICAL FIELD

[0001] The present disclosure relates to an additive manufacturing process with discharge plasma based heating, and more particularly to a disk holder assembly for attaching a plasma field applicator to a print head for plasma heating a printed part during the manufacturing process.

BACKGROUND

[0002] The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.

[0003] Three-dimensional printing, which is also referred to as additive manufacturing, creates printed components based on computer models. In one example, a printed component may be created by depositing a feedstock, such as a thermoplastic filament, through a heated nozzle in successive layers upon a base plate. Additive manufacturing techniques may be used to create large, relatively complex components. However, since additive manufacturing techniques involve building parts layer by layer, the resulting printed components exhibit an anisotropic tensile strength. That is, the tensile strength measured in the build direction of the printed component may be significantly less when compared to the tensile strength measured in a direction perpendicular to the build direction. [0004] In one approach to improve the tensile strength of a printed component in the build direction, electromagnetic energy may be used to fuse the successive layers of the printed component together. Specifically, the three-dimensional printer may include a plasma field applicator including a dielectric barrier discharge (DBD) based electrode that generates plasma. The plasma provides a conductive pathway between a point of extrusion located below the nozzle and the printed component. The conductive pathway enables heating of the printed component, or at least portions of the printed component proximate to the point of extrusion. The heat welds successive layers of the printed component together, thereby improving the tensile strength in the build direction. However, it is to be appreciated that DBD plasma-based heating requires accurate placement and alignment of the plasma field applicator around a print head of the three- dimensional printer.

SUMMARY

[0005] According to several aspects of the disclosure, a disk holder assembly for attaching a plasma field applicator to a print head for plasma heating a part during an additive manufacturing process is disclosed. The disk holder assembly includes a bracket for attaching to the print head, a carrier configured to hold a plasma field applicator in a fixed position for applying a plasma heat to a layer of filament being dispensed from the print head during the additive manufacturing process and a joint attaching the carrier and the bracket to one another. The joint moves the carrier relative to the bracket in at least one degree of freedom. [0006] In another aspect, the joint comprises a ball bearing, and at least one of the carrier and the bracket has a recess for receiving the ball bearing such that the carrier is movable on the ball bearing in two degrees of freedom.

[0007] In yet another aspect, the disk holder assembly includes a plurality of fasteners positioned around a perimeter of the carrier, wherein the fasteners fixedly hold the carrier in a position relative to the bracket.

[0008] In an aspect, the plurality of fasteners include at least one threaded fastener and at least one associated Belleville washer. The at least one threaded fastener and the at least one associated Belleville washer absorb vibration and deforming created by at least one of the carrier, the bracket, and the at least one threaded fastener thermally expanding.

[0009] In another aspect, the plurality of fasteners comprise of at least one pair of opposing threaded fasteners, where one of the pair of opposing threaded fasteners is a push screw that urges the bracket and the carrier away from one another and a remaining one of the pair of opposing threaded fasteners is pull screw that urges the bracket and the carrier toward one another.

[0010] In yet another aspect, the carrier comprises a first support member and a second support member that holds the plasma field applicator therebetween in the fixed position.

[0011] In an aspect, the first support member comprises a collar has an axis and an annular surface facing the axis. The annular surface of the collar surrounds and supports a peripheral surface of the plasma field applicator that faces radially outward from the axis of the collar. [0012] In another aspect, the collar comprises at least one flange extending radially inward from the annular surface toward the axis, wherein the at least one flange of the collar supports a bottom face of the plasma field applicator.

[0013] In yet another aspect, the second support member comprises a retaining ring with a shoulder that engages a top face of the plasma field applicator to retain the plasma field applicator within the collar.

[0014] In an aspect, the carrier includes a plurality of bolt fasteners for attaching the collar and the retaining ring together to clamp the plasma field applicator therebetween.

[0015] In another aspect, the disk holder assembly includes at least one bolt fastener that attaches the bracket to the print head and at least one dowel and at least one associated spring washer that couple the bracket and the print head to one another. [0016] In yet another aspect, a method for attaching a disk holder assembly to a plasma field applicator is disclosed. The plasma field applicator is attached to a print head. The method includes mounting the plasma field applicator to a carrier, wherein the disk holder assembly includes a bracket, the carrier, and a joint. The method also includes attaching the carrier to the bracket. The method also includes attaching the bracket to the print head. The method further includes moving the carrier to a predetermined position relative to the bracket to apply a plasma heat to a layer of filament being dispensed from the print head. Finally, the method includes applying a plurality of fasteners for holding the carrier in the predetermined position relative to the bracket.

[0017] In another aspect, the method further includes pivoting the carrier relative to the bracket by the joint of the disk holder assembly. [0018] In yet another aspect, the method includes absorbing, by at least one threaded fastener and at least one associated Belleville washer, a vibration and deforming created by thermal expansion of at least one of the carrier, the bracket, and the at least one threaded fastener.

[0019] In an aspect, the method includes urging, by at least one push screw, the bracket and the carrier away from one another, and urging, by at least one pull screw, the bracket and the carrier toward one another.

[0020] In another aspect, the method includes supporting a peripheral surface of the plasma field applicator that faces radially outward from an axis of a nozzle by an annular surface of a collar.

[0021] In yet another aspect, the method includes supporting, by at least one flange of the collar extending radially inward from the annular surface of the collar, a bottom face of the plasma field applicator.

[0022] In an aspect, the method includes engaging, by a retaining ring, a top face of the plasma field applicator to clamp the plasma field applicator within the collar.

[0023] In another aspect, the method includes attaching the collar and the retaining ring together to clamp the plasma field applicator therebetween by a plurality of bolt fasteners.

[0024] In yet another aspect, the method includes attaching, by at least one bolt fastener, the bracket to the print head, and coupling the bracket and the print head to one another by at least one dowel and at least one associated spring washer. DRAWINGS

[0025] FIG. 1 is a bottom perspective view of a gantry for a three-dimensional printer, illustrating a bottom portion of a print head carried by the gantry, with a disk holder assembly attaching a plasma field applicator to the print head.

[0026] FIG. 2 is an enlarged bottom perspective view of the bottom portion of the print head of FIG. 1 .

[0027] FIG. 3 is an upper perspective view of the print head of FIG. 1 , illustrating the print head having a nozzle for dispensing filament and the disk holder assembly.

[0028] FIG. 4 is an enlarged perspective cross-sectional view of the disk holder assembly and plasma field applicator of FIG. 3, illustrating the disk holder assembly having a bracket for attaching to the print head and a carrier for holding the plasma field applicator in a predetermined position relative to the bracket and the print head.

[0029] FIG. 5 is a schematic cross-sectional representation of a three-dimensional printer having the print head and the plasma field applicator of FIG. 3, illustrating the disk holder assembly positioning the plasma field applicator in the predetermined position for plasma heating the part while the nozzle applies filament during a layer build-up process. [0030] FIG. 6 is an upper perspective view of the disk holder assembly of FIG. 3.

[0031] FIG. 7 is a top plan view of the disk holder assembly of FIG. 3.

[0032] FIG. 8 is an exploded view of the disk holder assembly of FIG. 3.

[0033] FIG. 9 is a cross-sectional view of the disk holder assembly of FIG. 7 as taken along line 9-9, illustrating the disk holder assembly having a joint for moving the carrier about X and Y axes relative to the bracket, and the bracket having a height adjustment mechanism for moving the disk hold assembly linearly along a Z axis. [0034] FIG. 10 is a cross-sectional view of the disk holder assembly of FIG. 7 as taken along line 10-10, illustrating the disk holder assembly having fasteners for holding the carrier in the fixed predetermined position relative to the bracket.

[0035] FIG. 11 is a cross-sectional view of the disk holder assembly of FIG. 7 as taken along line 11-11 , illustrating the disk holder assembly having additional fasteners for holding the carrier in the fixed predetermined position relative to the bracket.

[0036] FIG. 12 is a flow chart of one example of a method for operating the disk holder assembly of FIG. 1 .

DETAILED DESCRIPTION

[0037] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0038] FIGS. 1 and 2 illustrate a bottom perspective view of a Cartesian gantry 100 with a side 102 for facing a build volume of a three-dimensional printer, and further with a print head apparatus 104 (“print head”) mounted to the gantry 100. FIG. 3 illustrates an upper perspective view of the print head 104 of FIGS. 1 and 2. As described in detail below, the print head 104 includes a disk holder assembly 106 for holding a plasma field applicator 108 in a predetermined position relative to the print head 104 and a part, such that plasma field applicator 108 transfers plasma heat to the part while the print head simultaneously prints the part during an additive manufacturing process. FIG. 4 illustrates an enlarged perspective cross-sectional view of the disk holder assembly 106 and the plasma field applicator 108 of FIG. 3. It is contemplated that other examples of the disk holder assembly can be used to hold the plasma field applicator in a predetermined position for transferring plasma heat to the part after the print head has printed the entire part.

[0039] Referring now to FIG. 5, a three-dimensional printer 110 includes a nozzle 112 and a part carrier 114 for supporting the printed part 118, in addition to the gantry 100 (FIGS. 1 and 2) and a delta-style structure or a robotic arm 120 (FIG. 3) that supports and moves the nozzle 112. The nozzle 112 defines a bore 122 extending along an axis 124 between first and second ends 126, 128.

[0040] The nozzle 112 deposits a filament 130 on the part carrier 114 or a previous layer 132 of the three-dimensional part 118. One of or both the nozzle 112 and the part carrier 114 are capable of movement in the X, Y, and Z directions, or a combination of these directions composing circular or curved patterns, for depositing the heated filament onto the previous layers 132 of the three-dimensional part 118.

[0041] The plasma field applicator 108 includes a high voltage electrode 134 encapsulated by a dielectric insulator 136. In this example, the plasma field applicator 108 is an octagonal-shaped silicon disk 138 that defines a centrally located aperture 140 with the second end 128 of the nozzle 112 extending through the aperture 140. The part carrier 114 grounds the three-dimensional part 118 to complete conduction pathways 146 that includes the plasma field applicator 108, an air gap 142 between the three- dimensional part 118 and the plasma field applicator 108, the grounded three-dimensional part 118, and the part carrier 114. The nozzle 112 is also grounded. As layers of the three- dimensional part 118 are fully or at least partially completed, the disk holder assembly 106 holds the plasma field applicator 108 in a predetermined position relative to the three- dimensional part 118 and the print head 104, such that the plasma field applicator 108 moves in sufficiently close proximity to the three-dimensional part 118 to place the three- dimensional part 118 under or incident with a plasma field 144 created by the plasma field applicator 108. The plasma field 144 completes the conduction pathway to directly couple the high voltage electrode 134 with the three-dimensional part 118. An electromagnetic field and induced conduction pathway 146 is, in addition to the plasma field 144, produced by the plasma field applicator 108. The plasma field 144 conductively couples the high voltage electrode 134 to the three-dimensional part 118 creating the electromagnetic field and induced conduction pathway 146 as shown emanating from the face of the plasma field applicator 108 traveling to the nozzle 112 of the print head 104.

[0042] The printer 110 further includes a controller 148, such as an electronic control device having a preprogrammed digital computer or processor, control logic, memory used to store data, and at least one I/O peripheral. The control logic includes a plurality of logic routines for monitoring, manipulating, and generating data. The controller 148 controls the operation the three-dimensional printer 110 and the plasma field applicator 108. The control logic may be implemented in hardware, software, or a combination of hardware and software. For example, control logic may be in the form of program code that is stored on the electronic memory storage and executable by the processor. The controller 148 provides control signals, generated by special software that creates pathways for the nozzle based on specific cross-section geometry that comes from a CAD model data program to the gantry, the nozzle 112, the plasma field applicator 108, and the part carrier 114 thus producing the three-dimensional part 118. The controller 148 may also modify the frequency, voltage, current, and waveform shape of the plasma. A further feature of the controller 148 is a signal generator 150 that outputs a high potential electromagnetic signal to the plasma field applicator 108. The signal generator 150 preferably provides an alternating current signal between 10-100 kHz to eliminate radiation and maximize conduction heating efficiency. However, any signal frequency or waveform shape may be used, including but not limited to continuous waves, square waves, triangle waves, short duration pulses, and rectified signals.

[0043] Referring generally to FIGS. 5-8, the disk holder assembly 106 includes a carrier 152 configured to hold the plasma field applicator 108 (FIGS. 4 and 5) in a fixed position relative to the print head 104 and the three-dimensional part 118 for applying the plasma heat to a layer 132 (FIG. 5) of the three-dimensional part 118. In this non-limiting example as described in detail below, the disk holder assembly 106 moves the plasma field applicator 108 in a linear direction vertically along the Z-axis and pivots about the X and Y axes until the plasma field applicator 108 is moved to the predetermined position. However, it is contemplated that other examples of the disk holder assembly can move the plasma field applicator along any linear or non-linear path and/or pivot the disk holder assembly relative to any one or more axes.

[0044] As best shown in FIGS. 4 and 5, in this non-limiting example, the carrier 152 includes first and second support members 156, 158 for holding the plasma field applicator 108 therebetween in the fixed position. The first support member 156 is a collar 160 having an axis 161 and an annular surface 162 surrounding and facing the axis 161. The annular surface 162 engages and supports a peripheral surface 164 of the plasma field applicator 108. The collar 160 includes one or more flanges 166 extending radially inward from the annular surface 162 and toward the axis 124, with the flanges 166 supporting a bottom face 168 of the plasma field applicator 108. Also, in this example, the second support member 158 is a retaining ring 170 with a shoulder 172 for engaging a top face 174 of the plasma field applicator 108 to retain the plasma field applicator 108 within the collar 160.

[0045] Each one of the collar 160 and the retaining ring 170 defines a plurality of holes 176 aligned with one another, and the carrier 152 includes a plurality of bolt fasteners 178 received in an associated one of the holes 176 for attaching the collar 160 and the retaining ring 170 together to clamp the plasma field applicator therebetween. The retaining ring 170 can include a carrier surface 180 that defines a first recess 182 (FIG. 9) and faces a bracket 184 for a joint as described below.

[0046] In this non-limiting example, the disk holder assembly 106 further includes a bracket 184 for attaching to the print head 104, and the bracket 184 includes one or more bolt fasteners 186 (FIG. 8) for attaching the bracket 184 to the print head 104. In this non-limiting example, the bracket 184 further includes one or more dowels 188 and one or more associated spring washers 190 for moving the disk holder assembly 106 and the plasma field applicator 108 linearly along the Z axis relative to the print head 104 to place the plasma field applicator 108 in the predetermined position for applying plasma heat to the part. In addition, the spring washers 190 can reduce vibration, decrease bolt creep, and deform in response to thermal expansion of any one or more components of the disk holder assembly. The bracket 184 includes first and second braces 192, 194 attached to one another by a plurality of threaded bolts 196 received in holes 197 formed in the associated first and second braces 192, 194. In this example, the first brace 192 can be a Y-shaped arm 198 defining holes 200 (FIG. 9) that receive an associated one of the bolt fastener 186 and the dowels 188 for attaching the bracket 184 to the print head 104 and moving the disk holder assembly 106 linearly along the Z-axis to the predetermined position. The second brace 194 can be a base ring 202 with a bracket surface 204 that faces the carrier 152 and defines a second recess 206 (FIG. 9). It is contemplated that other examples of the bracket can consist of a single piece or include more than 2 components, e.g., the first and second braces.

[0047] Referring to FIG. 9, the disk holder assembly 106 further includes a joint 208 attaching the carrier 152 and bracket 184 to one another for moving the carrier 152 relative to the bracket 184 in one or more degrees of freedom. In this non-limiting example, the joint 208 is a ball bearing 210, with at least one of the carrier 152 and the bracket 184 having a recess for receiving the ball bearing 210, such that the carrier 152 is movable on the ball bearing 210 in two degrees of freedom. Continuing with the previous example, the retaining ring 170 of the carrier 152 includes the carrier surface 180 with the first recess 182 facing the bracket 184, and the base ring 202 of the bracket 184 includes the bracket surface 204 with the second recess 206 that facing the carrier 152. The joint 208 further includes a plurality of fasteners 212 received within holes 213 formed along a perimeter 214 of the carrier 152 and the bracket 184 for fixedly holding the carrier 152 in a position relative to the bracket 184 when, for example, the plasma field applicator 108 is moved to the predetermined position for applying plasma heat to the part.

[0048] Referring to FIG. 10, in this non-limiting example, the fasteners 212 include one or more threaded fasteners 216 and one or more associated Belleville washers 218 for maintaining pressure on the joint 208, maintaining tension on the fasteners 216 to prevent bolt creep, and/or deform in response to thermal expansion of any components of the disk holder assembly. In this example, the fasteners include two threaded fasteners 216 and two associated sets of Belleville washers 218. However, it is contemplated that the fasteners can include more or fewer than two threaded fasteners and associated Belleville washers attaching any portion of the carrier to any portion of the bracket and/or adjusting the position of the carrier.

[0049] Referring to FIG. 11 , the fasteners 212 can further include one or more pairs of opposing threaded fasteners 220. Each pair of opposing threaded fasteners 220 can include a push screw 222 for urging the bracket 184 and the carrier 152 away from one another and a pull screw 224 for urging the bracket 184 and the carrier 152 toward one another. In this example, the fasteners 212 include two pairs of opposing threaded fasteners 220 (FIG. 8). However, it is contemplated that the fasteners can include more or fewer than two pairs of opposing threaded fasteners 220. In other examples, the disk holder assembly can include an articulated joint or any other suitable joint for moving the carrier and the plasma field applicator in any suitable direction relative to the bracket.

[0050] Referring to FIG. 12, a method 300 for using the disk holder assembly 106 of FIG. 1 to attach the plasma field applicator 108 to the print head 104 begins at block 302 with the plasma field applicator 108 being mounted to the carrier 152. The annular surface 162 of the collar 160 engages and supports the peripheral surface 164 of the plasma field applicator 108 that faces radially outward from the axis 124. The flanges 166 of the collar 160 support the bottom face 168 of the plasma field applicator 108. The retaining ring 170 engages the top face 174 of the plasma field applicator 108 to retain the plasma field applicator 108 within the collar 160. The bolt fasteners 178 are threadably received within the holes 176 to attach the collar 160 and the retaining ring 170 together and clamp the plasma field applicator 108 therebetween.

[0051] At block 304, the carrier 152 is attached to the bracket 184. Continuing with the previous non-limiting example, the threaded fasteners 216, the Belleville washers 218, the two pair of opposing threaded fasteners 220 attach the carrier 152 to the bracket 184. It is contemplated other suitable fasteners or joints can connect the bracket and carrier to one another.

[0052] At block 306, the bracket is attached to the print head. One or more bolt fasteners 186 attach the bracket 184 to the print head 104, and one or more dowels 188 and one associated spring washers 190 couple the bracket 184 and the print head 104 to one another. It is contemplated other suitable fasteners or joints can mount the bracket 184 to the print head 104.

[0053] At block 308, the carrier 152 is moved to a predetermined position relative to the bracket 184 for applying a plasma heat to the layer 132 of the three-dimensional part 118 being dispensed from the print head 104. In particular, the joint 208 pivots the carrier 152 relative to the bracket 184.

[0054] At block 310, the fasteners 212 are applied to the carrier 152 and the bracket 184 for holding the carrier 152 in the predetermined position relative to the bracket 184. One or more push screws 222 urge the bracket 184 and the carrier 152 away from one another, and one or more pull screws 224 urge the bracket 184 and the carrier 152 toward one another so as to prevent bolt creep and maintain the predetermined position of the carrier. Similarly, the Belleville washers 218 and the spring washers 190 prevent bolt creep and maintain the predetermined position of the carrier. [0055] At block 312, the Belleville washer 218 and the spring washers 190 absorb vibration and deform, in response to the carrier 152, the bracket 184, and/or the threaded fastener 216 thermally expanding.

[0056] The description of the present disclosure is merely exemplary in nature and variations that do not depart from the general sense of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.

[0057] Embodiments of the disclosure can be described with reference to the following numbered clauses, with specific features laid out in the dependent clauses: