Extruder head assembly and extruder screws for additive manufacturing machines

Abstract

An extruder head assembly for an additive manufacturing machine includes a supporting member defining a feed zone for receiving input material, a barrel defining a channel generally aligned with the feed zone, a heater assembly, a nozzle connected to the barrel, an extruder screw partially disposed in the channel and a motor operatively connected to the extruder screw. The extruder screw defines a screw axis, and includes an agitating portion that is disposed in the feed zone and that has an engaging surface, and an extruding portion that is disposed in the channel of the barrel, and that has a helical flight. The engaging surface is configured to engage input material, extends radially outwardly from the screw axis, and is oriented such that an angle between the engaging surface and a plane generally orthogonal to the screw axis is greater than a critical angle.

Description

EXTRUDER HEAD ASSEMBLY AND EXTRUDER SCREWS FOR ADDITIVE MANUFACTURING MACHINESCROSS-REFERENCE

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 570,860, entitled “Extruder Head Assembly and Extruder Screws for Additive Manufacturing Machines,” filed March 28, 2024, the entirety of which is incorporated by reference herein.TECHNICAL FIELD

[0002] The present technology relates to extruder head assemblies for additive manufacturing machines and extruder screws for additive manufacturing machines.BACKGROUND

[0003] Additive manufacturing machines, also referred to as 3D printers, have extruder head assemblies for outputting fabrication material. Fabrication material, for example in the form of pellets, is received in the extruder head assembly, and is heated until melted. The melted material is then extruded from the extruder head assembly to manufacture an item.

[0004] Conventionally, pellets have been used with larger additive manufacturing machines, in which extruder head assemblies have relatively powerful motors coupled to extruder screws. However, as pellets have become more accessible, there has been an interest in using this type of fabrication material with smaller additive manufacturing machines.

[0005] Downsizing conventional extruder head assemblies does present some challenges. Smaller extruder head assemblies can have less powerful motors. As a result, the extruder screw may be configured to apply less torque, which can make it more difficult for extruder screw to extrude material. In some instances, this may even lead to the extruder screw toget jammed by the fabrication material. Additionally, smaller extruder screws may get damaged when subjected to high loads. Furthermore, downsizing may limit the maximum size of the pellets that can be used.

[0006] Therefore, there is a desire for a technology that can overcome at least some of the above-described drawbacks.SUMMARY

[0007] It is an object of the present technology to ameliorate at least some of the inconveniences present in the prior art.

[0008] According to an aspect of the present technology, there is provided an extruder head assembly for an additive manufacturing machine. The extruder head assembly includes a supporting member, a barrel, a heater assembly, a nozzle, an extruder screw and a motor. The supporting member defines a feed zone configured to receive input material. The barrel defines a channel generally aligned with the feed zone, a proximate end portion of the barrel being connected to the supporting member. The heater assembly is in thermal communication with the barrel, and is selectively operable for heating the barrel. The nozzle is connected to a distal end of the barrel. The extruder screw is partially disposed in the channel of the barrel, and defines a screw axis. The extruder screw includes an agitating portion and an extruding portion. The agitating portion is disposed in the feed zone, and has an engaging surface configured to engage input material within the feed zone. The engaging surface extends radially outwardly from the screw axis. The engaging surface is oriented such that an angle between the engaging surface and a plane generally orthogonal to the screw axis is greater than a critical angle. The extruding portion extends below the agitating portion, is disposed in the channel of the barrel, and has a helical flight winding around the screw axis. The motor is operatively connected to the extruder screw for selectively causing the extruder screw to rotate about the screw axis.

[0009] In some embodiments, the engaging surface extends generally parallel to the screw axis.

[0010] In some embodiments, a radial width of the engaging surface is constant along a height thereof.

[0011] In some embodiments, a distal edge of the agitating portion is tapered.

[0012] In some embodiments, an upper end of the engaging surface has a first radial width, a lower end of the engaging surface has a second radial width, and the first radial width is greater than the second radial width.

[0013] In some embodiments, the barrel further defines a tapered inlet, and the engaging surface is shaped to be at least partially complementary to the tapered inlet.

[0014] In some embodiments, the engaging surface is a first engaging surface, and the agitating portion further includes a second engaging surface.

[0015] In some embodiments, the first and second engaging surfaces are spaced from one another by about 90 degrees.

[0016] In some embodiments, the first and second engaging surfaces are spaced from one another by about 180 degrees.

[0017] In some embodiments, a radial width of the first engaging surface is constant along a height thereof, and a radial width of the second engaging surface varies along a height thereof.

[0018] In some embodiments, the engaging surface is part of an agitator, the agitator being selectively connected to the extruder screw in the agitating portion.

[0019] In some embodiments, the engaging surface is integral with the helical flight.

[0020] In some embodiments, the extruder screw has a central shaft extending along at least a portion of the screw axis.

[0021] In some embodiments, the central shaft extends from a proximate end portion of the extruder screw to a distal end portion of the extruder screw, through the agitating portion and the extruding portion.

[0022] In some embodiments, a diameter of the central shaft varies between the proximate end portion of the extruder screw and the distal end portion of the extruder screw.

[0023] In some embodiments, the diameter of the central shaft has a minimum value in the agitating portion.

[0024] In some embodiments, the central shaft extends along a lower part of the extruding portion.

[0025] In some embodiments, the central shaft extends along all of the extruding portion.

[0026] In some embodiments, the diameter of the central shaft increases as a distance from the agitator portion increases.

[0027] In some embodiments, the diameter of the central shaft is constant through at least a distal end portion of the extruder screw.

[0028] In some embodiments, the helical flight defines an inner channel.

[0029] In some embodiments, a thickness of the helical flight around the inner channel is increased relative to a thickness of the helical flight around the central shaft.

[0030] In some embodiments, an angle between the helical flight and a plane orthogonal to the screw axis is greater than the critical angle.

[0031] In some embodiments, the input material is one of: standard pellets, micro-pellets, and chopped filaments.

[0032] In some embodiments, the nozzle is selectively connected to the barrel.

[0033] In some embodiments, the supporting member further comprises a filling funnel portion connected to the supporting member, the filling funnel portion being configured to funnel the input material toward the feed zone.

[0034] In some embodiments, the extruder head assembly measures / weighs about 1.5 kg.

[0035] According to another aspect of the present technology, there is provided an additive manufacturing machine including a frame, a printer bed supported by the frame, and an extruder head assembly according to the above aspect or according to the above aspect and one or more of the above embodiments, the extruder head assembly being connected to the frame, and a controller supported by the frame, and operatively connected to the extruder head assembly.

[0036] In some embodiments, the extruder head assembly is moveable such that input material is configured to flow in a generally vertically downward direction.

[0037] According to another aspect of the present technology, there is provided an extruder screw for an additive manufacturing machine, the extruder screw defines a screw axis, and includes an agitating portion and an extruding portion. The agitating portion has an engaging surface extending radially outwardly from the screw axis. The engaging surface is oriented such that an angle between the engaging surface and a plane generally orthogonal to the screw axis is greater than a critical angle. The extruding portion extends below the agitating portion, and has a helical flight winding around the screw axis.

[0038] In some embodiments, the engaging surface extends generally parallel to the screw axis.

[0039] In some embodiments, a radial width of the engaging surface is constant along a height thereof.

[0040] In some embodiments, a distal edge of the agitating portion is tapered.

[0041] In some embodiments, an upper end of the engaging surface has a first radial width, a lower end of the engaging surface has a second radial width, and the first radial width is greater than the second radial width.

[0042] In some embodiments, the engaging surface is a first engaging surface, and the agitating portion further includes a second engaging surface.

[0043] In some embodiments, the first and second engaging surfaces are spaced from one another by about 90 degrees.

[0044] In some embodiments, the first and second engaging surfaces are spaced from one another by about 180 degrees.

[0045] In some embodiments, a radial width of the first engaging surface is constant along a height thereof; and a radial width of the second engaging surface varies along a height thereof.

[0046] In some embodiments, the extruder screw has a central shaft extending along at least a portion of the screw axis

[0047] In the context of the present specification, unless expressly provided otherwise, the words “first”, “second”, “third”, etc. have been used as adjectives only for the purpose of allowing for distinction between the nouns that they modify from one another, and not for the purpose of describing any particular relationship between those nouns.

[0048] It must be noted that, as used in this specification and the appended claims, the singular form “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0049] As used herein, the term “about” in the context of a given value or range refers to a value or range that is within 20%, preferably within 10%, and more preferably within 5% of the given value or range.

[0050] As used herein, the term “and / or” is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example, “A and / or B” is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

[0051] For purposes of the present application, terms related to spatial orientation when referring to an additive manufacturing machine and components in relation to the additive manufacturing machine, such as “vertical”, “horizontal”, “forwardly”, “rearwardly”, “above” and “below”, are as they would be understood by a person standing in front of the additive manufacturing machine.

[0052] Embodiments of the present technology each have at least one of the above- mentioned objects and / or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and / or may satisfy other objects not specifically recited herein.

[0053] Additional and / or alternative features, aspects, and advantages of embodiments of the present technology will become apparent from the following description, the accompanying drawings, and the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0054] For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0055] Figure 1 is a top plan view of an extruder head assembly;

[0056] Figure 2 is a cross-sectional view of the extruder head assembly of Figure 1 taken along the line 2-2 of Figure 1;

[0057] Figure 3 is a close-up of part of the extruder head assembly of Figure 2;

[0058] Figure 4 is a perspective view taken from a top, front, left side of an additive manufacturing machine having an extruder head assembly according to an embodiment of the present technology;

[0059] Figure 5 is a perspective view taken from a top, front, left side of an alternative additive manufacturing machine having an extruder head assembly according to an embodiment of the present technology;

[0060] Figure 6 is a perspective view taken from a top, front, right side of the extruder head assembly of Figure 4;

[0061] Figure 7 is a front elevation view of the extruder head assembly of Figure 4;

[0062] Figure 8 is a cross-sectional view of the extruder head assembly of Figure 4 taken along the line 8-8 of Figure 7;

[0063] Figures 9, 10 and 11 are close-up, cross-sectional views of portions of the extruder head assembly of Figure 4;

[0064] Figure 12A is a front elevation view of part of a heater assembly, a barrel, a nozzle and an extruder screw of the extruder head assembly of Figure 4;

[0065] Figure 12B is a cross-sectional view of the part of the heater assembly, the barrel, the nozzle and the extruder screw of Figure 12A taken along the line 12B-12B of Figure 12 A;

[0066] Figure 13 A is a perspective view taken from a bottom front side of the extruder screw of Figure 12 A;

[0067] Figure 13B is a front elevation view of the extruder screw of Figure 13A;

[0068] Figure 13C is a side elevation view of the extruder screw of Figure 13A;

[0069] Figure 13D is a cross-sectional view of the extruder screw of Figure 13A taken along the line 13D-13D of Figure 13C;

[0070] Figure 13E is a perspective view taken from bottom, rear, left side of an upper portion of the extruder screw of Figure 13 A;

[0071] Figure 13F is a perspective view taken from bottom, front, right side of the upper portion of the extruder screw of Figure 13 A;

[0072] Figure 14A is a perspective view taken from a bottom, front side of an extruder screw according to an alternative embodiment of the present technology;

[0073] Figure 14B is a front elevation view of the extruder screw of Figure 14A;

[0074] Figure 14C is a side elevation view of the extruder screw of Figure 14A;

[0075] Figure 14D is a cross-sectional view of the extruder screw of Figure 14A taken along the line 14D-14D of Figure 14C;

[0076] Figure 15A is a perspective view taken from a bottom, front side of an extruder screw according to another embodiment of the present technology;

[0077] Figure 15B is a front elevation view of the extruder screw of Figure 15 A;

[0078] Figure 15C is a side elevation view of the extruder screw of Figure 15 A;

[0079] Figure 15D is a cross-sectional view of the extruder screw of Figure 15A taken along the line 15D-15D of Figure 15C;

[0080] Figure 16A is a perspective view taken from a bottom, front side of an extruder screw according to yet another embodiment of the present technology;

[0081] Figure 16B is a front elevation view of the extruder screw of Figure 16 A;

[0082] Figure 16C is a side elevation view of the extruder screw of Figure 16A;

[0083] Figure 16D is a cross-sectional view of the extruder screw of Figure 16A taken along the line 16D-16D of Figure 16C;

[0084] Figure 17A is a perspective view taken from a bottom, front side of an extruder screw according to yet another embodiment of the present technology;

[0085] Figure 17B is a right side elevation view of the extruder screw of Figure 17 A;

[0086] Figure 17C is a left side elevation view of the extruder screw of Figure 17A;

[0087] Figure 17D is a cross-sectional view of the extruder screw of Figure 17A taken along the line 17D-17D of Figure 17B;

[0088] Figure 18A is a perspective view taken from a bottom, front side of an extruder screw according to yet another embodiment of the present technology;

[0089] Figure 18B is a right side elevation view of the extruder screw of Figure 18 A;

[0090] Figure 18C is a left side elevation view of the extruder screw of Figure 18 A;

[0091] Figure 18D is a cross-sectional view of the extruder screw of Figure 18A taken along the line 18D-18D of Figure 18B;

[0092] Figure 19A is a perspective view taken from a bottom, front side of an extruder screw according to yet another embodiment of the present technology;

[0093] Figure 19B is a rear elevation view of the extruder screw of Figure 19A;

[0094] Figure 19C is a front elevation view of the extruder screw of Figure 19 A;

[0095] Figure 19D is a cross-sectional view of the extruder screw of Figure 19A taken along the line 19D-19D of Figure 19B;

[0096] Figure 20A is a perspective view taken from a bottom, front side of an extruder screw according to yet another embodiment of the present technology;

[0097] Figure 20B is a rear elevation view of the extruder screw of Figure 20A;

[0098] Figure 20C is a front elevation view of the extruder screw of Figure 20 A;

[0099] Figure 20D is a cross-sectional view of the extruder screw of Figure 20A taken along the line 20D-20D of Figure 20B;

[0100] Figure 21A is a perspective view taken from a bottom, front side of an extruder screw according to yet another embodiment of the present technology;

[0101] Figure 2 IB is a front elevation view of the extruder screw of Figure 21 A;

[0102] Figure 21C is a side elevation view of the extruder screw of Figure 21 A; and

[0103] Figure 21D is a cross-sectional view of the extruder screw of Figure 21 A taken along the line 21D-21D of Figure 21C.

[0104] Unless otherwise noted, the Figures may not be drawn to scale.DETAILED DESCRIPTION

[0105] The present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including". "comprising", or "having", "containing", "involving" and variations thereof herein, is meant to encompass the items listed thereafter as well as, optionally, additional items. In the following description, the same numerical references refer to similar elements.

[0106] Referring to Figures 1 to 3, an extruder head assembly 20 having an extruder screw 22 is shown. To overcome some limitations of the prior art, a helical flight 24 of the extruder screw 22 has been shortened along a height of the extruder screw 22. More specifically, the helical flight 24 has been shortened such that a top of the helical flight 24 does not extend into a feed zone 26 of the extruder head assembly 20. This can assist limiting likelihood of the extruder screw 22 from jamming or shearing pellets in the feed zone 26. However, this can lead to additional problems. For example, the input material 116 can form a self-supporting structure, which may be referred to as a “bridge” (shown in Figure 3) around a shaft 28 of the extruder screw 22, which can prevent input material from flowing toward a bottom of the extruder screw 22.

[0107] Referring to Figure 4, an additive manufacturing machine 50 having an extruder head assembly 100 according to a non-limiting embodiment of the present technology is shown. More specifically, the additive manufacturing machine 50 is a three- dimensional printer (3D printer) 50. The 3D printer 50 includes a frame 52, a printer bed 54 supported by the frame 52, the extruder head assembly 100, which is operatively connected to the frame 52, and a controller 58 (schematically shown) supported by the frame 52 and operatively connected to the extruder head assembly 100. The extruder head assembly 100, the illustrated embodiment, has been scaled down such that it weighs about 1.5 kg, and measures about 250 mm in height. It is contemplated that a weight and size ofthe extruder head assembly 100 may vary from one embodiment to another. For instance, the current technology could be additionally implemented in larger machines than the present examples.

[0108] The frame 52 has a base 60, a front wall 62, side walls 64, a rear wall 66, and a top wall 68. The base 60 and the front, side, rear and top walls 60, 62, 64, 66 and 68 define an enclosed printing space. The front wall 62 has a window 63 which allows to look at the enclosed printing space. It is contemplated that in some embodiments, the window 63 could be omitted, and the front wall 62 could simply define an aperture. The top wall 68 defines an aperture 69, which, inter alia, enables the extruder head assembly 100 to move relative to the frame 52. It is also contemplated that in some embodiments, the front, side, rear and top walls 60, 62, 64, 66 and 68 could be omitted, and the frame 52 could have columns disposed at each corner thereof. The frame 52 also includes a moveable member 70, which generally extends between the side walls 64. The moveable member 70 is moveable between the front and rear walls 60, 66 by actuator as (not shown) which are communicatively connected to the controller 58. It is contemplated that in some embodiments, the frame 52 could include additional moveable members. The moveable member 70 is connected to the extruder head assembly 100 via a carriage (not shown), which enables the extruder head assembly 100 to move along the moveable member 70.

[0109] The printer bed 54, as mentioned above, is supported by the frame 52. More specifically, the printer bed 54 is moveably connected to the rear wall 66. In some embodiments, the printer bed 54 could be moveably connected to the base 60. Indeed, the printer bed 54, which has a flat upper surface, is moveable in the vertical direction by actuators (not shown) that are communicatively connected to the controller 58. It is contemplated that in some embodiments, the printer bed 54 could be generally fixed relative to the frame 52. For instance, the printer bed 54 could be connected to the base 60 such that the printer bed 54 would only be vertically moveable to adjust a horizontal level thereof (e.g., raising or lowering a corner of the printer bed 54). In such instances, the extruder head assembly 100 would be moveable in the vertical direction.

[0110] The controller 58, which is communicatively or operatively connected to a number of components of the 3D printer 50, is configured to control various elements of the 3D printer 50, including operation of the extruder head assembly 100.

[0111] Referring now to Figure 5, another additive manufacturing machine 51 having the extrusion head assembly 100 is shown. The additive manufacturing machine 51 is an articulated robot arm 51. In the illustrated embodiment, the articulated robot arm 51 has six degrees of freedom, but it is contemplated that this may vary from one embodiment of the articulated robot arm to another.

[0112] With reference to Figures 6 to 11, the extruder head assembly 100 according to an embodiment of the present technology will now be described in greater detail. The extruder head assembly 100 includes a supporting member 102 having a filling funnel portion 104, a motor 106, a barrel 110, a heater assembly 112, a nozzle 114 and an extruder screw 200.

[0113] The supporting member 102, as will become apparent from the below description, supports various components of the extruder head assembly 100. The supporting member 102 defines a feed zone 130. The feed zone 130 is an internal chamber that is configured to receive the input material 116 therein. In the illustrated embodiment, the feed zone 130 is depicted as a cylindrical chamber, but it is contemplated that the feed zone 130 may vary in shape, size and orientation.

[0114] The input material 116, also referred to as fabrication material, is a plurality of pellets 116 (schematically shown as circles in Figure 8). In some implementations of the 3D printer 50, the input material 116 may be standard pellets, micro-pellets, chopped filaments or flakes. Thus, it is understood that the shape and / or size of the input material 116 may vary from one embodiment to another. Henceforth, the input material 116 will be referred to as pellets 116.

[0115] The pellets 116 can be guided into the feed zone 130 of the supporting member 102 from the filling funnel portion 104 due to gravity. The filling funnel portion 104, which is connected to the supporting member 102, may in turn receive the pellets 116from a container (not shown) disposed vertically higher than the filling funnel portion 104 or from a pneumatic distribution system (not shown).

[0116] The motor 106 is connected to supporting member 102. In some instances, the motor 106 may be disposed in and / or supported by the supporting member 102. The motor 106 is further operatively connected to the extruder screw 200, for, as will be described below, selectively causing rotation of the extruder screw 200 about a screw axis 201.

[0117] The barrel 110 is also connected to the supporting member 102. More specifically, the barrel 110 has a proximate end portion 142 and a distal end portion 144. The proximate end portion 142 is connected to the supporting member 102 and is thus disposed closer to the supporting member 102 than the distal end portion 144. At a top of the proximate end portion 142, the barrel 110 defines a tapered inlet 145 (see Figure 10). A top of the tapered inlet 145 is wider than a bottom of the tapered inlet 145. The top of the tapered inlet 145 is the same size as a bottom of the feed zone 130. In some embodiments, the top of the tapered inlet 145 and a bottom of the feed zone 130 may not be the same size. Below the tapered inlet 145, the barrel 110 defines a channel 146. As will be described in greater detail below, the channel 146 is configured to receive part of the extruder screw 200 therein.

[0118] The barrel 110 is positioned, relative to the supporting member 102, so that the channel 146 is operationally aligned with the feed zone 130. This enables the pellets 116 to flow from the feed zone 130 to the channel 146 via, inter alia, gravity. In the present embodiment, a center of the channel 146 is aligned with a center of the feed zone 130. However, it is contemplated that while the channel 146 and the feed zone 130 may be operationally aligned with one another, the center of the channel 146 may be offset from a center of the feed zone 130. For example, in one embodiment, the feed zone 130 could be larger than the top of the tapered inlet 145, and the channel 146 could be offset from a center of the feed zone 130.

[0119] With additional reference to Figures 12A and 12B, the heater assembly 112 is operatively connected to the supporting member 102 and in thermal contact with thebarrel 110. Specifically, the heater assembly 112 surrounds the barrel 110 in the illustrated embodiment. It is contemplated that the configuration and form of the heater assembly 112 could vary in different embodiments. In the illustrated embodiment, the heater assembly 112 has two heating elements 113 that are selectively operable to heat the barrel 110 for melting the pellets 116 received in the channel 146. It is contemplated that there could be more or fewer heating elements. The heating elements 113 are configured to provide two heating zones in order to better control the melting process of the pellets 116. It is contemplated there could be one or three or more heating zones. In some embodiments, the heating assembly 112 may include sensors communicatively connected to the controller 58 for sensing a temperature of the barrel 110. In some instances, a number of sensors could be greater than a number of heating elements 113, for obtaining abetter temperature profile.

[0120] The nozzle 114 is connected to the barrel 110, at the distal end portion 144 thereof. In the illustrated embodiment, the nozzle 114 is selectively fastened to the nozzle 114 via threads. The nozzle 114 can thus be replaced by another nozzle if desired. In other embodiments, the nozzle 114 may be fixedly connected to the barrel 110 (e.g., the nozzle 114 may be integral with the barrel 110). The nozzle 114 defines an aperture 115. During operation, melted pellets 116 flow out of the aperture 115.

[0121] With additional reference to Figures 13A to 13F, the extruder screw 200 will now be described in greater detail.

[0122] The extruder screw 200 defines the screw axis 201 about which the extruder screw 200 turns. In the accompanying Figures, the extruder head assembly 100, and thus the extruder screw 200, is positioned such that screw axis 201 extends generally vertically. When the extruder head assembly 100 is installed in the 3D printer 50, the screw axis 201 will remain in the vertical orientation. When the extruder head assembly 100 is connected to the articulated robot arm 51, it is noted that the extruder head assembly 100 may be tilted such that the screw axis 201 may be angled relative to the vertical at some points during operation. During standard operation, however, the screw axis 201 will remain vertical, or near vertical, in orientation.

[0123] The extruder screw 200 has a proximal end portion 202 and a distal end portion 203, both of which are generally aligned with one another along the screw axis 201. In more detail, the extruder screw 200 has an agitating portion 204, an extruding portion 206 extending along the screw axis 201 below the agitating portion 204 and a shank portion 208 extending along the screw axis 201 above the agitating portion 204. The extruding portion 206 includes a feeding section Fs, a compression section Cs and the metering section Ms. In some instances, the presence and / or size of the feeding, compression and metering sections could be omitted.

[0124] The extruder screw 200 further has a central shaft 210 that extends along a portion of the screw axis 201. More specifically, the central shaft 210 extends from the proximate end portion 202 to the distal end portion 203. Thus, the central shaft 210 extends through the agitating portion 204 and the extruding portion 206. In some embodiments, the central shaft 210 can also be said to extend through the shank portion 208. As will be described below, it is contemplated that the central shaft 210 may only extend along part of the extruder screw 200 (e.g., the central shaft 210 may only extend along the extruding portion 206).

[0125] A diameter of the central shaft 210 varies along the screw axis 201, i.e., the central shaft 210 is tapered between the proximate end portion 202 and the distal end portion 203. More specifically, the diameter of the central shaft 210 increases from the proximate end portion 202 toward the distal end portion 203, and then remains constant at a lower end of the distal end portion 203. Thus the central shaft 210 has a tapered section and a uniform section. The central shaft 210 has a minimum shaft diameter at theproximate end portion 202 and a maximum shaft diameter Dmax near the distal end portion 203. The extremity of the distal end portion 203 has conic point, but the specific end shape could vary. The tapered configuration (i.e., the smaller diameter toward the proximate end portion 202) provides space between central shaft 210 and an inner surface of the barrel 110 such that input material larger in size can be used. As the pellets 116 melt during operation, the increase in the diameter of the central shaft 210 reduces the space for material received therein and thus assists in compressing the melting pellets 116. Finally, the centralshaft 210 having a constant diameter assists in effective metering of the melted pellets 116 out of the nozzle 114 during operation.

[0126] The extruding portion 206, which is received in the channel 146, has a helical flight 220 that winds around the screw axis 201 and the central shaft 210. It is contemplated that in some embodiments, there may be two or more helical flights. In some embodiments, the one of the additional helical flights may be a barrier flight. In the illustrated embodiment, the helical flight 220 extends radially outwardly from the central shaft 210. The helical flight 220 spans all of a height of the extruding portion 206. The extruder screw 200 and the extruding portion 206 are configured such that the helical flight 220 begins at a top of the channel 146 (i.e., at a bottom of the tapered inlet 145) and extends generally to a bottom of the extruding portion 206. Thus, the helical flight 220 does not substantially extend into the feed zone 130. This aids in reducing the possibility of the pellets 116 jamming or shearing by the helical flight 220 in the larger feed zone 130.

[0127] The helical flight 220 is oriented so as to have a surface along a helix angle a. Referring to Figure 13B, the helix angle a is defined between part of the helical flight 220 and a horizontal plane HP. In the present technology, the helix angle a is greater than a critical angle. The critical angle corresponds to the angle below which the helical flight 220 begins applying shearing forces to the pellets 116 while the extruder screw 200 is rotating. Thus, during rotation of the extruder screw 200, if a surface has an angle greater than the critical angle, then the pellets 116 can generally be driven downward through the barrel 110 without experiencing shearing forces or the pellets 116 can rotate with the extruder screw 200 without being stuck (jammed) or pinched between the helical flight 220 and an inner surface of the barrel. In some instances, the pellets 116 can, in part, be guided downward via gravity. If the surface has an angle less than the critical angle, the pellets 116 may undergo shearing forces during operation. By the present technology, the helix angle a is limited to be greater than the critical angle to minimize shearing. Shearing exerts torque on the extruder screw 200. As the present technology aims to reduce the size and weight of the extruder head assembly 100, the extruder screw 200 is smaller than screws of the prior art, and thus more susceptible to be stuck (e.g., a blockage of the pellets 116between the helical flight 220 and the inner surface of the barrel 110 prevents rotation of the extruder screw 200) and / or be damaged from shearing melt material.

[0128] Still referring to Figures 12A, 12B and 13A to 13F, the agitating portion 204, which is mostly received in the feed zone 130, will now be described in greater detail. The agitating portion 204 has an engaging surface 252 and an engaging surface 254. It is contemplated that in other embodiments, the agitating portion 204 could have more than two engaging surfaces. In the present embodiment, the engaging surfaces 252, 254 are, with respect to the screw axis 201, angularly spaced from one another by about 90 degrees (and alternatively by 270 degrees). As will be described below, it is contemplated that the engaging surfaces 252, 254 may be angularly spaced from one another by more or less than 90 degrees. The engaging surfaces 252, 254 are continuous with corresponding surfaces of the helical flight 220. It can thus be said that the engaging surfaces 252, 254 are integral with the helical flight 220.

[0129] The engaging surfaces 252, 254 extend radially outwardly from the central shaft 210 (and thus from the screw axis 201). In the present embodiment, the engaging surfaces 252, 254 extend radially outwardly from the central shaft 210 by the same amount across a whole height thereof. That is, the engaging surfaces 252, 254 have a constant radial width Wr. Additionally, the engaging surfaces 252, 254 are oriented such that they are both parallel to the screw axis 201. Thus, the engaging surfaces 252, 254 are oriented generally vertically. As a result, an angle between the engaging surfaces 252, 254 and a corresponding horizontal plane is 90 degrees, and therefore greater than the critical angle such that the engaging surfaces 252, 254 are configured to not apply shearing forces on pellets 116.

[0130] It will be noted that the configuration of the agitating portion 204, namely the presence of the engaging surfaces 252, 254 can strengthen portions of the extruder screw 200, which can, in some instances, aid in preventing damage to the extruder screw 200 when the extruder screw 200 is jammed.

[0131] The shank portion 208 is configured to operatively connect to the motor 106, such that in response to the motor 106 being actuated, the extruder screw 200 rotatesabout the screw axis 201. It is contemplated that various types of gearing and the like may be implemented in different embodiments to operatively connect the shank portion 208 to the motor 106. In some embodiments, the shank portion 208 may be omitted, and a top of the agitating portion 204 may be operatively connected to the motor 106.

[0132] With reference to Figures 14A to 14D, an alternative embodiment of the extruder screw 200, namely an extruder screw 300, will now be described. Features of the extruder screw 300 similar to those of the extruder screw 200 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0133] The extruder screw 300 notably differs from the extruder 200 in that the central shaft 210 has a larger diameter along the screw axis 201. The central shaft 210 is still tapered, and still has a constant diameter at a lower end of the distal end portion 203. The Dmin of the extruder screw 300 is greater than the Dmin of the extruder screw 200, and the Dmax of the extruder screw 300 is greater than the Dmax of the extruder screw 200. An increase in size of the central shaft 210, can assist in reinforcing the extruder screw 300 so that it can withstand higher stresses, which can occur, for example, when the extruder screw 300 applies shearing forces to the pellets 116 via the helical flight 220. However, as a result of an increase in the diameter of the central shaft 210, a clearance area provided between central shaft 210 and the inner surface of the barrel 110 is reduced, such that the size of the pellets 116 that can be used may also be reduced.

[0134] With reference to Figures 15A to 15D, another embodiment of an extruder screw 400 according to the present technology will now be described. Features of the extruder screw 400 similar to those of the extruder screw 300 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0135] The extruder screw 400 includes an agitator 402. The agitator 402, which has the engaging surfaces 252, 254, is selectively connected to the extruder screw 400 in the agitating portion 204. In some instances, the agitator 402 could be retrofitted onto existing extruder screws that do not have an agitator portion. It is contemplated that the agitator 402 may be connected to the extruder screw 200 in a variety of ways, including welding, fastening, by interference fit or brazing.

[0136] With reference to Figures 16A to 16D, another embodiment of an extruder screw 500 according to the present technology will now be described. Features of the extruder screw 500 similar to those of the extruder screw 200 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0137] In this embodiment, the central shaft 210 is only defined along a portion of the extruding portion 206. That is, the central shaft 210 does not extend along the entirety from the proximal end portion 202 to the distal end portion 203. Thus, the central shaft 210 is not defined in the agitating portion 204, nor at the top of the extruding portion 206. Instead, an inner channel 502, which is generally aligned with the screw axis 201, is defined from a top of the extruder portion 206 to, approximately, a top end of the central shaft 210. The inner channel 502 is defined in part by the helical flight 220. A thickness of the helical flight 220 can be increased around the inner channel 502 for reinforcing the extruder screw 500 the inner channel 502 in some embodiments, thereby compensating for the partial absence of the central shaft 210. The presence of the inner channel 502 (and the partial absence of the central shaft 210) may enable the use of larger pellets 116 in some cases. Likewise, a thickness of the agitating portion 204 may also be increased to compensate for the absence of the central shaft 210 therein.

[0138] With reference to Figures 17A to 17D, another embodiment of an extruder screw 600 according to the present technology will now be described. Features of the extruder screw 600 similar to those of the extruder screw 200 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0139] The extruder screw 600 has an engaging surface 652 and an engaging surface 654. The engaging surface 652 is the same as the engaging surface 252 and will thus not be described herewith. The engaging surface 654, on the other hand, differs from the engaging surface 254 notably in that the engaging surface 654 is tapered, such that a width of the engaging surface 654 varies along a height of the agitating portion 204.

[0140] A top of the engaging surface 654 has an upper width Wu. In some embodiments, the upper width Wu is sized such that the engaging surface 654 almost engages an inner wall of the feed zone 130, i.e. the outer edge of the engaging surface 654creates a scraping effect to move pellets 116 from the inner wall of the feed zone 130. A bottom of the engaging surface 654 has a lower width Wl. In some embodiments, the lower width Wl is generally equal to a width of the helical flight 220. The upper width Wu is greater than the lower width Wl. In some embodiments, part of the engaging surface 254 could be configured to be generally complementary to the tapered inlet 145 and / or to part of the feed zone 130.

[0141] It will be noted that while the engaging surface 654 is tapered along the screw axis 201, the engaging surface 654 remains parallel to the screw axis 201, and thus to the engaging surface 652. It is contemplated that in some embodiments, the engaging surface 652 could also be tapered, like the engaging surface 654.

[0142] With reference to Figures 18A to 18D, another embodiment of an extruder screw 700 according to the present technology will now be described. Features of the extruder screw 700 similar to those of the extruder screw 200 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0143] The extruder screw 700 has an engaging surface 752 and an engaging surface 754. The engaging surface 752 is the same as the engaging surface 252 and will thus not be described herewith. The engaging surface 754, on the other hand, differs from the engaging surface 254 notably in that the engaging surface 754, and a distal edge thereof, is partially helical. More precisely, the engaging surface 754 is oriented such that it is at an angle with respect to a corresponding horizontal plane. However, the angle is greater than the critical angle, such that the engaging surface 754 does not induce shearing forces on the pellets 116.

[0144] With reference to Figures 19A to 19D, another embodiment of an extruder screw 800 according to the present technology will now be described. Features of the extruder screw 800 similar to those of the extruder screw 200 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0145] In this embodiment, the engaging surfaces 252, 254, are spaced from one another by about 180 degrees. This can, in some instances, reduce vibration within the extruder head assembly 100 when the extruder head assembly 100 is in operation.

[0146] With reference to Figures 20A to 20D, another embodiment of an extruder screw 900 according to the present technology will now be described. Features of the extruder screw 900 similar to those of the extruder screw 200 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0147] In this embodiment, the engaging surfaces 252, 254, are spaced from one another by about 180 degrees.

[0148] Additionally, the central shaft 210 is only defined along a portion of the extruding portion 206 (i.e., the central shaft 210 does not extend from the proximal end portion 202 to the distal end portion 203). Thus, the central shaft 210 is not defined in the agitating portion 204, nor at the top of the extruding portion 206. Instead, the extruder screw 900 defines an inner channel 902 that is generally aligned with the screw axis 201, and that extends from a top of the agitating portion 204 to, approximately, a top end of the central shaft 210. The inner channel 902 is defined in part by the helical flight 220. A thickness of the helical flight 220 may be increased around the inner channel 902 in some cases to reinforce the extruder screw 900 around the inner channel 902, and thereby compensate for the partial absence of the central shaft 210. For example, referring to Figure 20C, the thickness T1 of the helical flight 220 around the inner channel 902 is greater than the thickness T2 of the helical flight 220 around the central shaft 210. The presence of the inner channel 902 (and the partial absence of the central shaft 210) may enable the use of larger pellets 116.

[0149] With reference to Figures 21 A to 21D, another embodiment of an extruder screw 1000 according to the present technology will now be described. Features of the extruder screw 1000 similar to those of the extruder screw 200 have been labeled with the same reference numerals and will not be re-described in detail herewith.

[0150] In this embodiment, the agitating portion 204 has a segment 1010 that is continuous and integral with the helical flight 220, and that has the engaging surface 252, 254. The agitating portion 204 further has a segment 1012 that extends radially outwardly from the central shaft 210, and that is not continuous with the helical flight 220. The segment 1012 has engaging surfaces 1052, 1054. The presence of additional engaging surfaces can assist in further agitating the pellets 116 while the extruder screw 1000 is rotating.

[0151] Referring back to Figures 8 to 11, 12A, 12B and 13A to 13F, and to the extruder screw 200, the extruder head assembly 100 in operation will now be described. It will be understood that the extruder head assembly 100 using the extruder screws 300, 400, 500, 600, 700, 800, 900, 1000 would operate in a similar manner.

[0152] During operation, the heating elements 113 of the heater assembly 112 are turned on. The heating elements 113 heat the barrel 110 until a predetermined temperature is reached. In some instances, the predetermined temperature may be greater than the melting temperature of the pellets 116. In other instances, the predetermined temperature could be below the melting temperature of the pellets 116. As the effective melting temperature of different pellets 116 could vary depending on base material, additives, etc., the pre-determined temperature may not in some cases be specifically tuned to the melting temperature of the pellets 116 used.

[0153] The motor 106 is turned on, which causes the extruder screw 200 to rotate about the screw axis 201, and as will be described below, push the pellets 116 downwardly toward the nozzle 114.

[0154] During operation, pellets 116 are received in the feed zone 130 via the filling funnel portion 104. Initially, the pellets 116 moves toward with the channel 146 of the barrel 110 due to gravity, but as the rate of pellets 116 entering the feed zone 130 may be greater than the rate of pellets 116 entering the channel 146, the feed zone 130 may get filled with the pellets 116.

[0155] Despite the large number of pellets 116 in the feed zone 130, the agitating portion 204 ensures that the pellets 116 do not form a “bridge”, allowing the pellets 116 to be continuously fed into the tapered inlet 145 and the channel 146. Indeed, the engaging surfaces 252, 254 engage the pellets 116 within the feed region 130 to keep them moving, and therefore prevent the self-supporting structure from forming. The continuous agitation of the pellets 116, is in part due to the non-circular cross-section of the extruder screw 200 in the feed zone 130. It can be said that the engaging surfaces 252, 254 are off-centered. It will also be noted that since the engaging surfaces 252, 254 are angled to be greater than the critical angle, the engagement between the agitating portion 204 and the pellets 116 does not cause shearing of the pellets 116.

[0156] Since the extruder screw 200 is rotating about the screw axis 201, once pellets 116 reach a top of the channel 146, which coincides with the beginning of the helical flight 220, the pellets 116 are pushed downward (i.e., extruded toward a bottom of the barrel 110). Sometimes, some pellets 116 may get stuck between the helical flight 220 and the inner surface of the barrel 110. In this case, due to the helix angle a being greater than the critical angle, the pellets 116 are pushed down without being subjected to shearing stresses. In other instances, the pellets 116 are subjected to shearing stresses, but because of their mechanical properties and due to the barrel 110 being heated, the pellets 116 are deformed. The additional strength provided by the agitating portion 204 to the extruder screw 200 can assist in preventing damage to the screw in such scenarios.

[0157] As the pellets 116 move toward the nozzle 114, due to the heater assembly 112, the pellets 116 begin and / or continue to melt to form a continuous melt. Eventually, as the diameter of the central shaft 210 increases, the at least partially melted pellets 116 start to get compressed to get rid of air and increase pressure.

[0158] Eventually the melted pellets 116 reach the maximum shaft diameter Dmax of the extruder screw 200. The maximum shaft diameter Dmax being constant toward the nozzle 114 can ensure that the rate of melted pellets 116 being moved toward the nozzle114 is generally constant. The melted pellet material is then extruded out of the aperture115 of the nozzle 114.

[0159] It will be appreciated that the motor 106 can be selectively stopped to stop extrusion out of the aperture 115, and be selectively operable to cause the extruder screw 200 to rotate in the opposing direction, for stopping flow out of the nozzle 114.

[0160] Thus, embodiments of the present technology enable effective downscaling of extruder head assemblies and extruder screws from large additive manufacturing machines to smaller additive manufacturing machines by overcoming challenges that would otherwise arise. Indeed, the extruder head assembly and the extruder screws according to the present technology can have smaller sizes and use less powerful motors, but can be less likely to jam during operation, can disrupt formation of stagnant pellets in the feed zone, can utilize pellets of smaller and / or larger sizes.

[0161] Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the appended claims.

Claims

What is claimed is:

1. An extruder head assembly for an additive manufacturing machine, the extruder head assembly comprising: a supporting member defining a feed zone configured to receive input material; a barrel defining a channel generally aligned with the feed zone, a proximate end portion of the barrel being connected to the supporting member; a heater assembly in thermal communication with the barrel, the heater assembly being selectively operable for heating the barrel; a nozzle connected to a distal end of the barrel; an extruder screw partially disposed in the channel of the barrel, the extruder screw defining a screw axis, the extruder screw comprising: an agitating portion disposed in the feed zone, the agitating portion having an engaging surface configured to engage input material within the feed zone, the engaging surface extending radially outwardly from the screw axis, the engaging surface being oriented such that an angle between the engaging surface and a plane generally orthogonal to the screw axis is greater than a critical angle; and an extruding portion extending below the agitating portion, the extruding portion being disposed in the channel of the barrel, the extruding portion having a helical flight winding around the screw axis, and a motor operatively connected to the extruder screw for selectively causing the extruder screw to rotate about the screw axis.

2. The extruder head assembly of claim 1, wherein the engaging surface extends generally parallel to the screw axis.

3. The extruder head assembly of claim 1 or 2, wherein a radial width of the engaging surface is constant along a height thereof.

4. The extruder head assembly of claim 1 or 2, wherein a distal edge of the agitating portion is tapered.

5. The extruder head assembly of claim 4, wherein: an upper end of the engaging surface has a first radial width, a lower end of the engaging surface has a second radial width, and the first radial width is greater than the second radial width.

6. The extruder head assembly claim 4 or 5, wherein the barrel further defines a tapered inlet, and the engaging surface is shaped to be at least partially complementary to the tapered inlet.

7. The extruder head assembly of claim 1 or 2, wherein the engaging surface is a first engaging surface, and the agitating portion further includes a second engaging surface.

8. The extruder head assembly of claim 7, wherein the first and second engaging surfaces are spaced from one another by about 90 degrees.

9. The extruder head assembly of claim 7, wherein the first and second engaging surfaces are spaced from one another by about 180 degrees.

10. The extruder head assembly of any one of claims 7 to 9, wherein: a radial width of the first engaging surface is constant along a height thereof; and a radial width of the second engaging surface varies along a height thereof.

11. The extruder head assembly of any one of claims 1 to 10, wherein the engaging surface is part of an agitator, the agitator being selectively connected to the extruder screw in the agitating portion.

12. The extruder head assembly of any one of claims 1 to 10, wherein the engaging surface is integral with the helical flight.

13. The extruder head assembly of any one of claims 1 to 12, wherein the extruder screw has a central shaft extending along at least a portion of the screw axis.

14. The extruder head assembly of claim 13, wherein the central shaft extends from a proximate end portion of the extruder screw to a distal end portion of the extruder screw, through the agitating portion and the extruding portion.

15. The extruder head assembly of claim 14, wherein a diameter of the central shaft varies between the proximate end portion of the extruder screw and the distal end portion of the extruder screw.

16. The extruder head assembly of claim 15, wherein the diameter of the central shaft has a minimum value in the agitating portion.

17. The extruder head assembly of claim 13, wherein the central shaft extends along a lower part of the extruding portion.

18. The extruder head assembly of claim 13, wherein the central shaft extends along all of the extruding portion.

19. The extruder head assembly of claim 17 or 18, wherein the diameter of the central shaft increases as a distance from the agitator portion increases.

20. The extruder head assembly of any one of claims 17 to 19, wherein the diameter of the central shaft is constant through at least a distal end portion of the extruder screw.

21. The extruder head assembly of any one of claims 17 to 20, wherein the helical flight defines an inner channel.

22. The extruder head assembly of claim 21, wherein a thickness of the helical flight around the inner channel is increased relative to a thickness of the helical flight around the central shaft.

23. The extruder head assembly of any one of claims 1 to 22, wherein an angle between the helical flight and a plane generally orthogonal to the screw axis is greater than the critical angle.

24. The extruder head assembly of any one of claims 1 to 23, wherein the input material is one of: standard pellets, micro-pellets, and chopped filaments.

25. The extruder head assembly of any one of claims 1 to 24, wherein the nozzle is selectively connected to the barrel.

26. The extruder head assembly of any one of claims 1 to 25, wherein the supporting member further comprises a filling funnel portion connected to the supporting member, the filling funnel portion being configured to funnel the input material toward the feed zone.

27. The extruder head assembly of any one of claims 1 to 26, wherein the extruder head assembly weighs about 1.5 kg.

28. An additive manufacturing machine comprising: a frame; a printer bed supported by the frame; the extruder head assembly of any one of claims 1 to 27 connected to the frame; and a controller supported by the frame, and operatively connected to the extruder head assembly.

29. An additive manufacturing machine comprising: a robotic arm; and the extruder head assembly of any one of claims 1 to 27 connected to the robotic arm.

30. The additive manufacturing machine of claim 28 or 29, wherein the extruder head assembly is moveable such that input material is configured to flow in a generally vertically downward direction.

31. An extruder screw for an additive manufacturing machine, the extruder screw defining a screw axis, and comprising: an agitating portion having an engaging surface extending radially outwardly from the screw axis, the engaging surface being oriented such that an angle between the engaging surface and a plane generally orthogonal to the screw axis is greater than a critical angle; and an extruding portion extending below the agitating portion, the extruding portion having a helical flight winding around the screw axis.

32. The extruder screw of claim 31, wherein the engaging surface extends generally parallel to the screw axis.

33. The extruder screw of claim 31 or 32, wherein a radial width of the engaging surface is constant along a height thereof.

34. The extruder screw of claim 31 or 32, wherein a distal edge of the agitating portion is tapered.

35. The extruder screw of claim 34, wherein: an upper end of the engaging surface has a first radial width, a lower end of the engaging surface has a second radial width, and the first radial width is greater than the second radial width.

36. The extruder screw of claim 31 or 32, wherein the engaging surface is a first engaging surface, and the agitating portion further includes a second engaging surface.

37. The extruder screw of claim 36, wherein the first and second engaging surfaces are spaced from one another by about 90 degrees.

38. The extruder screw of claim 36, wherein the first and second engaging surfaces are spaced from one another by about 180 degrees.

39. The extruder screw of any one of claims 36 to 38, wherein: a radial width of the first engaging surface is constant along a height thereof; and a radial width of the second engaging surface varies along a height thereof.

40. The extruder screw of any one of claims 31 to 40, wherein the extruder screw has a central shaft extending along at least a portion of the screw axis.

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