WO2022146864A1

WO2022146864A1 - Pellet extruder for additive manufacturing

Info

Publication number: WO2022146864A1
Application number: PCT/US2021/065048
Authority: WO
Inventors: Nelson ZAMBRANA
Original assignee: Metallum3D, Inc.
Priority date: 2020-12-30
Filing date: 2021-12-23
Publication date: 2022-07-07

Abstract

A pellet extruder for additive manufacturing comprises a barrel, a short feed screw, one or more heater elements, a melt pump, and a nozzle. The pellet extruder is adapted to form a granular column of material inside the barrel that progressively melts and pushes material inside the barrel within a material temperature transition zone and a material melt zone. Melted material is extruded through the nozzle.

Description

PELLET EXTRUDER FOR ADDITIVE MANUFACTURING

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63/132,187, entitled “PELLET EXTRUDER FOR ADDITIVE MANUFACTURING”, filed December 30, 2020. The entire contents of the foregoing application is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present application relates to extruders for additive manufacturing, and more particularly, a pellet extruder.

BACKGROUND

[0003] Fused Deposition Modeling (FDM) is an additive manufacturing method where successive layers of a thermoplastic material are extruded to build a three-dimensional object. FDM can be performed using piston extruders, filament extruders, or screw extruders. Some extruders utilize a positive displacement pump to provide precise control of material extrusion through a nozzle. Conventional extruders can be problematic, including by way of interrupted material feeding during material replenishment or during the 3D printing process, high-cost materials, heat creep, and limited material flow rates of the extruders.

SUMMARY

[0004] In one example embodiment, the present disclosure is directed to a pellet extruder for additive manufacturing. The pellet extruder can include a barrel, a short feed screw, one or more heater elements, a melt pump, and a nozzle. The barrel can comprise a barrel inlet that defines a material feed zone, and a barrel outlet that defines a material melt zone. The barrel can define a material temperature transition zone. The melt pump can define a material extrusion zone associated with the nozzle.

[0005] In the foregoing pellet extruder, the barrel outlet can be connected to a melt pump inlet of the melt pump. The one or more heater elements can be mounted to the barrel within the material melt zone. The melt pump can be configured to be actively heated. The pellet extruder can comprise a heat sink mounted to the barrel within the material temperature transition zone.

[0006] A granular column of material can form inside the barrel and substantially act as a piston by progressively melting and pushing material inside the barrel within the material temperature transition zone and the material melt zone. The pellet extruder can be adapted to generate a positive pressure associated with the melt pump based at least in part on a volumetric material input flow associated with the material feed zone and a volumetric material output flow associated with the material extrusion zone. The positive pressure can be at a melt pump inlet of the melt pump. The volumetric material input flow can be of the short feed screw, and the volumetric material output flow can be through the nozzle.

[0007] In one example embodiment, the present disclosure is directed to a method that comprises feeding, by a short feed screw, pelletized material into a barrel that is adapted to form a granular column of the pelletized material; heating, by one or more heater elements, the pelletized material in the barrel to form a melted material, wherein the granular column pushes the melted material into a melt pump; and extruding the melted material through a nozzle in a material extrusion zone.

[0008] In the foregoing method, the short feed screw can be configured to operate so that it does not operate beyond a material temperature transition zone. The granular column can be divided between the material temperature transition zone and a material melt zone.

[0009] In the foregoing method, the one or more heater elements cause the material melt zone to be heated. The method can include generating a positive pressure associated with the melt pump based at least in part on a volumetric material input flow associated with a material feed zone and a volumetric material output flow associated with the material extrusion zone. In some examples, generating the positive pressure associated with the melt pump comprises: causing, by a first motor, the short feed screw to be driven; and causing, by a second motor, the melt pump to be driven.

[00010] The foregoing example embodiments and other example embodiments will be explained in further detail in the follow description.

BRIEF DESCRIPTION OF THE DRAWINGS

[00011] The accompanying drawings illustrate only example embodiments of a pellet extruder and method and therefore are not to be considered limiting of the scope of this disclosure. The principles illustrated in the example embodiments of the drawings can be applied to alternate extruder and methods. Additionally, the elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Certain dimensions or positions may be exaggerated to help visually convey such principles. In the drawings, the same reference numerals used in different embodiments designate like or corresponding, but not necessarily identical, elements.

[00012] FIG. 1 shows an example of a piston extruder in accordance with various embodiments of the present disclosure.

[00013] FIG. 2 shows an example of a piston extruder with a positive displacement pump in accordance with various embodiments of the present disclosure.

[00014] FIG. 3 shows an example of a filament extruder in accordance with various embodiments of the present disclosure.

[00015] FIG. 4 shows an example of a filament extruder with a positive displacement pump in accordance with various embodiments of the present disclosure.

[00016] FIG. 5 shows an example of a screw extruder in accordance with various embodiments of the present disclosure.

[00017] FIG. 6 shows an example of a screw extruder with a positive displacement pump in accordance with various embodiments of the present disclosure.

[00018] FIGS. 7A and 7B show examples of a pellet extruder in accordance with various embodiments of the present disclosure.

[00019] FIG. 8 shows a flow chart of a method for additive manufacturing in accordance with example embodiments of the present disclosure.

DETAILED DESCRIPTION

[00020] The present disclosure relates to a pellet extruder for additive manufacturing that can utilize a granular column of pelletized material within a barrel to substantially act as a piston and push material into a melt pump for extrusion. The volumetric input flow of material and the volumetric output flow through the nozzle can be set such that there is a positive pressure generated at a melt pump inlet of the melt pump.

[00021] In some examples, the pellet extruder can be used for Fused Deposition Modeling (FDM). FDM is an additive manufacturing method where successive layers of a thermoplastic material can be extruded to build a three-dimensional object. Several examples of thermoplastic extruders are described below.

[00022] A first example of 3D printing extruder is the piston extruder 100a as shown in FIG. 1. In the piston extruder 100a pelletized thermoplastic material can be heated inside a heated chamber and pushed out the extruder through a nozzle.

[00023] A second example of 3D printing extruder is the piston extruder with a positive displacement pump 100b as shown in FIG. 2. This type of extruder adds a positive displacement pump to the piston extruder 100a to provide precise control of the material extrusion.

[00024] A third example of 3D printing extruder is the filament extruder 100c as shown in FIG. 3. In the filament extruder 100c, the thermoplastic material can be pre-formed into a continuous filament of circular cross section. The filament effectively becomes a continuously melting piston which pushes the material through the nozzle.

[00025] A fourth example of 3d printer extruder is the filament extruder with a positive displacement pump lOOd as shown in FIG. 4. This type of extruder adds a positive displacement pump to the filament extruder 100c to increase the volumetric flow of material through the nozzle.

[00026] A fifth example of 3D printer extruder is the screw extruder lOOe as shown in FIG. 5. In the screw extruder lOOe, pelletized thermoplastic material can be continually fed into a heated barrel that contains a rotating compression screw. The screw can push the thermoplastic material through the barrel progressively melting and pushing it through the nozzle.

[00027] A sixth example of 3D printing extruder is the screw extruder with a positive displacement pump lOOf as shown in FIG. 6. This type of extruder adds a positive displacement pump to the screw extruder lOOe to provide precise control of the material extrusion through the nozzle. Some advantages and disadvantages of the six examples of extruders are summarized below.

EXTRUDER TYPE ADVANTAGES DISADVANTAGES

Piston Extruder 1-Uses low cost pelletized 1 -Difficult to precisely control materials material extrusion.

2-Interruption of the 3D printing process for material replenishment

Piston Extruder with 1-Uses low cost pelletized 1 -Interruption of 3D printing

Positive Displacement Pump materials process for material

2-Precise control of material replenishment extrusion

Filament Extruder 1 -Precise control of material 1- Uses higher cost filament extrusion materials

2-Interruption of the 3D printing process to replenish filament material

3 -Maximum material flow rate limited by strength of filament material

Filament Extruder with 1 -Precise control of material 1-Uses higher cost filament

Positive Displacement Pump extrusion conditions, materials

2-Provides for high material 2-Interruption of the 3D flow rates printing process to replenish filament material

Screw extruder 1-Uses low cost pelletized 1 -Length of extrusion feed materials screw

2-Provides for high material 2-Screw performance depends flow rates on material shear flow

3 -Allows for continuous properties uninterrupted 3D printing 3 -Difficult to precisely control material extrusion

4-Heat creep to material feed zone requires cooling of the extrusion feed screw

Screw extruder with 1-Uses low cost pelletized 1 -Length of extrusion feed

Positive Displacement Pump material screw

2-Precise control of materials of 2-Screw performance depends material extrusion on material shear flow

3 -Provides for high material properties flow rates 3 -Heat creep to material feed

4-Allows for continuous zone requires cooling of the uninterrupted 3D printing extrusion feed screw

[00028] The present disclosure can combine elements of the piston extruders 100a, 100b, the filament extruders 100c, lOOd, and the screw extruders lOOe, lOOf, among other things. Additionally, the present disclosure describes the use of a zero compression short feed screw to create a granular column of material within a barrel that has an actively cooled material temperature transition zone, and a heated material melt zone. The granular column of material can act as a piston which can feed material with positive pressure to the melt pump for extrusion through the nozzle.

[00029] In the following paragraphs, particular embodiments will be described in further detail by way of example with reference to the drawings. In the description, well-known components, methods, and/or processing techniques are omitted or briefly described. Furthermore, reference to various feature(s) of the embodiments is not to suggest that all embodiments must include the referenced feature(s).

[00030] Referring now to FIGS. 7A and 7B, shown is a pellet extruder 200 in accordance with various embodiments of the present disclosure. The pellet extruder 200 can include a pellet material hopper 203, a pellet material feed box 206, a short feed screw 209, a heat sink 212, one or more heater element(s) 215, a barrel 218, a melt pump 221, and a nozzle 224. One or more motor(s) 227, for example a motor 227a or a motor 227b, can be provided as shown in FIG. 7B.

[00031] The pellet material hopper 203 can be configured for loading of pelletized material 201 (e.g., material in pelletized form) and to discharge the pelletized material 201 to the pellet material feed box 206. The pellet material feed box 206 can be coupled to the pellet material hopper 203.

[00032] The short feed screw 209 can comprise a suitable screw for feeding the pelletized material 201 to the barrel 218. The short feed screw 209 can comprise a screw diameter, a screw circumference, a screw pitch, and a number of helical flights. Operation of the short feed screw 209 can comprise a screw swept area, a swept helix distance, a screw fill factor, a screw volume output per revolution, or a screw volume output per screw revolution. In some examples, the short feed screw 209 is a zero compression screw.

[00033] The heat sink 212 can be provided for reducing heat in one or more zones defined by the pellet extruder 200. In some examples, the heat sink 212 comprises a number of fins for conducting heat. The one or more heater element(s) 215 can comprise a cartridge heater or other suitable heater for heating the pelletized material 201.

[00034] The barrel 218 can comprise a barrel inlet 219 and a barrel outlet 220. The barrel inlet 219 can be sized and shaped to receive the short feed screw 209. The barrel outlet 220 can be mechanically connected to the melt pump 221 (e.g., at a melt pump inlet 222 of the melt pump 221).

[00035] The melt pump 221 can be configured to be actively heated, for example with elements that actively surround the melt pump 221 with heat energy rather than relying solely on conduction from other heated bodies. The melt pump 221 can comprise one or more gear(s). The one or more gear(s) can comprise a gear pitch, one or more teeth, a pitch diameter, an outside diameter, a gear thickness, a gear face area without teeth, a gear face area with teeth, a gear tooth cavity total area, a gear tooth cavity total volume, and a cavity volume per tooth. Operation of the melt pump 221 can comprise a melt pump volume output per revolution.

[00036] The nozzle 224 can be configured to extrude small amounts of thermoplastic or other material to form layers. The one or more motor(s) 227, including the motor 227a or the motor 227b, can be configured to drive various components of the pellet extruder 200. For example, the motor 227a can drive the short feed screw 209 and the motor 227b can drive the melt pump 221.

[00037] In operation, the pellet extruder 200 can be configured to create or define a material feed zone 233, a material temperature transition zone 236, a material melt zone 239, and a material extrusion zone 242. The barrel inlet 219 can be associated with or define the material feed zone 233. The barrel 218 can be associated with or define the material temperature transition zone 236. The barrel outlet 220 can be associated with or define the material melt zone 239. The heat sink 212 can be mounted to the barrel 218 within the material temperature transition zone 236. The melt pump 221, when connected to the nozzle 224, can be associated with or define the wherein the material extrusion zone 242.

[00038] The short feed screw 209 can feed the pelletized material 201 from the pellet material feed box 206 into the barrel 218. The short feed screw 209 can be configured to operate so that it does not extend or operate beyond a material temperature transition zone 236 that is actively cooled. The short feed screw 209 can operate without cooling. [00039] The pellet extruder 200 can be configured to feed the pelletized material 201 into the barrel 218 to form a granular column 207. The pellet extruder 200 can substantially create a granular column 207 that can push a melted material into the melt pump 221 for extrusion through the nozzle 224 in the material extrusion zone 242. In some examples, the short feed screw 209 comprises a zero compression screw that feeds the granular column 207 without compressing the granular column 207.

[00040] Some examples of the pellet extruder 200 can operate without requiring a piston or a screw that compresses material within the barrel 218. The barrel 218 can form the granular column 207 inside the barrel 218. Operation of the pellet extruder 200 can allow the progressive melting and pushing of material inside the barrel 218 within the material temperature transition zone 236 and the material melt zone 239. In some examples, the pellet extruder 200 is configured so the granular column 207 can substantially act as a piston.

[00041] The pellet extruder 200 can be adapted to generate a positive pressure associated with the melt pump 221. The positive pressure can be based at least in part on a volumetric material input flow associated with the material feed zone 233 and a volumetric material output flow associated with the material extrusion zone 242.

[00042] A volumetric material input flow of the short feed screw 209 and a volumetric material output flow through the nozzle 224 can be set such that there is a positive pressure generated at the melt pump inlet 222 of the melt pump 221. Examples for volumetric flow rates of the short feed screw 209 and the melt pump 221 are described herein.

Short Feed Screw 209

Short Feed Screw 209 Volume Output Per Screw Revolution = screw swept area) x (swept helix distance) x (screw fill factor) (1)

Melt Pump

Melt Pump 221 Volume Output Per Screw Revolution =

(# of gears) x ( # of teeth per gear) x (cavity volume per tooth) (2)

[00043] The disclosed calculations show that the volumetric output (per revolution) of the melt pump 221 can be greater than the volumetric output (per revolution) of the short feed screw 209. The motors 227 can separately and independently cause the short feed screw 209 and the melt pump 221 to be driven. In some examples, the motor 227a can drive the short feed screw 209 and the motor 227b can drive the melt pump 221. The speed of the one or more motor(s) 227 can be set to equalize the output volumes or slightly increase the output of the volume of the short feed screw 209 over the output volume of the melt pump 221 to cause a volumetric flow differential resulting in a positive pressure at the melt pump inlet 222 of the melt pump 221.

[00044] The granular column can be divided between the material temperature transition zone 236 and the material melt zone 239. Operation of the one or more heater element(s) 215 can cause the material melt zone 239 to be heated. For example, the one or more heater element(s) 215 can be mounted to the barrel 218 within the material melt zone 239. The one or more heater element(s) 215 can be configured to actively apply heat energy to the barrel 218.

[00045] Referring now to FIG. 8, an example method 800 is illustrated in accordance with the embodiments of this disclosure. Example method 800 comprises operations for additive manufacturing using the example pellet extruder 200 described herein. In alternate embodiments, certain steps of the method 800 may be performed in parallel, in a different order, or may be eliminated and other steps may be added to the example method.

[00046] At box 805, the short feed screw 209 can feed the pelletized material 201 into the barrel 218. The barrel 218 can be adapted to form a granular column 207 of the pelletized material 201. The granular column 207 can be divided between the material temperature transition zone 236 and the material melt zone 239. The short feed screw 209 can be configured to operate so that it does not operate beyond the material temperature transition zone 236.

[00047] At box 810, the one or more heater element(s) 215 can cause the material melt zone 239 to be heated. The one or more heater element(s) 215 can heat the pelletized material 201 in the barrel 218 to form a melted material. The granular column 207 can push the melted material into the melt pump 221.

[00048] At box 815, the method 800 can include generating a positive pressure associated with the melt pump 221 based at least in part on a volumetric material input flow associated with the material feed zone 233 and a volumetric material output flow associated with the material extrusion zone 242. Generating the positive pressure associated with the melt pump 221 can include causing, by the one or more motors 227, at least one of the short feed screw 209 or the melt pump 221 to be driven. In some examples, the first motor 227a causes the short feed screw 209 to be driven, and the second motor 227b causes the melt pump 221 to be driven. The volumetric material input flow can be, in some examples, associated with the volume output per screw revolution of the short feed screw 209.

[00049] At box 820, the melted material can be extruded through the nozzle 224 in the material extrusion zone 242. Thereafter, the operations can proceed to completion.

[00050] With respect to the example methods described herein, it should be understood that in alternate embodiments, certain steps of the methods may be performed in a different order, may be performed in parallel, or may be omitted. Moreover, in alternate embodiments additional steps may be added to the example methods described herein. Accordingly, the example methods provided herein should be viewed as illustrative and not limiting of the disclosure.

[00051] Similarly, for any apparatus shown and described herein, one or more of the components may be omitted, added, repeated, and/or substituted. Accordingly, embodiments shown in a particular figure should not be considered limited to the specific arrangements of components shown in such figure. Further, if a component of a figure is described but not expressly shown or labeled in that figure, the label used for a corresponding component in another figure can be inferred to that component. Conversely, if a component in a figure is labeled but not described, the description for such component can be substantially the same as the description for the corresponding component in another figure.

[00052] Referring generally to the examples herein, any components of the pellet extruder described herein can be made from a single piece (e.g., as from a mold, injection mold, die cast, 3-D printing process, extrusion process, stamping process, or other prototype methods). In addition, or in the alternative, a component of the pellet extruder can be made from multiple pieces that are mechanically coupled to each other. In such a case, the multiple pieces can be mechanically coupled to each other using one or more of a number of coupling methods, including but not limited to epoxy, welding, fastening devices, compression fittings, mating threads, and slotted fittings. One or more pieces that are mechanically coupled to each other can be coupled to each other in one or more of a number of ways, including but not limited to couplings that are fixed, hinged, removeable, slidable, and threaded.

[00053] Terms such as “first”, “second”, “top”, “bottom”, “side”, “distal”, “proximal”, and “within” are used merely to distinguish one component (or part of a component or state of a component) from another. Such terms are not meant to denote a preference or a particular orientation, and are not meant to limit the embodiments described herein. In the example embodiments described herein, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[00054] Although example embodiments are described herein, it should be appreciated by those skilled in the art that various modifications are well within the scope of this disclosure. Those skilled in the art will appreciate that the example embodiments described herein are not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the example embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments using the present disclosure will suggest themselves to practitioners of the art. Therefore, the scope of the example embodiments is not limited herein.

Claims

1. A pellet extruder for additive manufacturing, comprising: a barrel; a short feed screw; one or more heater elements; a melt pump; and a nozzle.

2. The pellet extruder of claim 1, wherein the melt pump is configured to be heated.

3. The pellet extruder of claim 1, wherein the barrel comprises a barrel inlet and a barrel outlet, wherein the barrel defines: a material feed zone with the barrel inlet; a material temperature transition zone; and a material melt zone with the barrel outlet.

4. The pellet extruder of claim 3, wherein the short feed screw does not extend beyond the material temperature transition zone.

5. The pellet extruder of claim 3, wherein the barrel outlet is connected to a melt pump inlet of the melt pump.

6. The pellet extruder of claim 3, further comprising a heat sink mounted to the barrel within the material temperature transition zone.

7. The pellet extruder of claim 3, wherein the one or more heater elements are mounted to the barrel within the material melt zone and are actively heated.

8. The pellet extruder of claim 3, wherein a granular column of material forms inside the barrel and substantially acts as a piston by progressively melting and pushing material inside the barrel within the material temperature transition zone and the material melt zone.

9. The pellet extruder of claim 3, wherein the melt pump defines a material extrusion zone.

10. The pellet extruder of claim 9, wherein the pellet extruder is adapted to generate a positive pressure associated with the melt pump based at least in part on a volumetric material input flow associated with the material feed zone and a volumetric material output flow associated with the material extrusion zone.

11. The pellet extruder of claim 10, wherein the positive pressure is at a melt pump inlet of the melt pump.

12. The pellet extruder of claim 10, wherein the volumetric material input flow is of the short feed screw.

13. The pellet extruder of claim 10, wherein the volumetric material output flow is through the nozzle.

14. The pellet extruder of claim 1, wherein the short feed screw is a zero compression screw.

15. A method, comprising: feeding, by a short feed screw, pelletized material into a barrel that is adapted to form a granular column of the pelletized material; heating, by one or more heater elements, the pelletized material in the barrel to form a melted material, wherein the granular column pushes the melted material into a melt pump; and extruding the melted material through a nozzle in a material extrusion zone.

16. The method of claim 15, wherein the short feed screw is configured to operate so that it does not operate beyond a material temperature transition zone.

17. The method of claim 16, wherein the granular column is divided between the material temperature transition zone and a material melt zone.

18. The method of claim 17, wherein the one or more heater elements cause the material melt zone to be heated.

19. The method of claim 15, further comprising: generating a positive pressure associated with the melt pump based at least in part on a volumetric material input flow associated with a material feed zone and a volumetric material output flow associated with the material extrusion zone.

20. The method of claim 19, wherein generating the positive pressure associated with the melt pump comprises: causing, by a first motor, the short feed screw to be driven; and causing, by a second motor, the melt pump to be driven.

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