LIQUEFIER FOR AN EXTRUSION-BASED ADDITIVE MANUFACTURING SYSTEM AND METHOD FOR ITS MANUFACTURING

Abstract

A liquefier tube (5) of an extrusion head (4) for use in an extrusion-based additive manufacturing system (1). The liquefier tube (5) describes a passageway (P) having an inlet portion (57) and an outlet (55) downstream of the inlet portion (57). The inlet portion (57) has a substantially circular cross-section for receipt of a filament of material. The passageway (P) transitions from the inlet portion (57) to a non-circular portion (53) downstream of the inlet portion (57) and having a non-circular cross-section.

Claims

1. A liquefier for use in an extrusion-based additive manufacturing system, the liquefier describing a passageway having an inlet portion with a substantially circular cross-section for receipt of a filament of material and an outlet downstream of the inlet portion, wherein the passageway transitions from the inlet portion to a non-circular portion downstream of the inlet and has a substantially circular portion downstream of the non-circular portion, the non-circular portion having a non-circular cross-section.

2. A liquefier according to claim 1, wherein the non-circular portion comprises a plurality of segments, each having a different cross-sectional shape or configuration.

3. A liquefier according to claim 2, wherein a minor dimension of a first of the segments is greater than a minor dimension of a second of the segments, which is downstream of the first segment.

4. A liquefier according to claim 2, wherein a minor dimension of a first segment and a corresponding minor dimension of a second segment are rotationally offset from one another.

5. A liquefier according to claim 2 , wherein the passageway comprises a substantially circular portion intermediate a first segment and a second segment.

6. (canceled)

7. A liquefier according to claim 1 , wherein the passageway comprises a substantially circular portion at or toward the outlet.

8. A liquefier according to claim 1 , wherein the substantially circular portion and the non-circular portion have substantially equal cross-sectional areas.

9. A liquefier according to claim 1, comprising a tubular body.

10. A liquefier according to claim 9, wherein the tubular body has a substantially constant wall thickness.

11. A liquefier according to claim 1, wherein the outlet comprises an extrusion tip for dispensing material in a molten state.

12. A liquefier according to claim 1, wherein the liquefier is made of metal.

13. A liquefier according to claim 11 in combination with a heating element for heating a filament of material received, in use, within the liquefier.

14-25. (canceled)

26. A liquefier for use in an extrusion-based additive manufacturing system, the liquefier describing a passageway having an inlet portion with a substantially circular cross-section for receipt of a filament of material and an outlet downstream of the inlet portion, wherein the passageway transitions from the inlet portion to a non-circular portion downstream of the inlet, the non-circular portion having a non-circular cross-section and a plurality of segments, each having a different cross-sectional shape or configuration with a minor dimension of a first segment and a corresponding minor dimension of a second segment being rotationally offset from one another.

27. A liquefier according to claim 26, wherein the passageway comprises a substantially circular portion intermediate the first segment and the second segment.

28. A liquefier according to claim 26, wherein the passageway comprises a substantially circular portion downstream of the non-circular portion.

29. A liquefier according to claim 28, wherein the passageway comprises a substantially circular portion at or toward the outlet.

30. A liquefier according to claim 26, wherein the substantially circular portion and the non-circular portion have substantially equal cross-sectional areas.

31. A liquefier according to claim 26 comprising a tubular body.

32. A liquefier according to claim 31, wherein the tubular body has a substantially constant wall thickness.

33. A liquefier according to claim 26, wherein the outlet comprises an extrusion tip for dispensing material in a molten state.

34. A liquefier according to claim 26, wherein the liquefier is made of metal.

35. A liquefier according to claim 26 in combination with a heating element for heating a filament of material received, in use, within the liquefier.

36. A method of manufacturing a liquefier for use in an extrusion-based additive manufacturing system, the method comprising providing a first block of material, machining a first part of a liquefier into a surface of the first block, providing a second block of material, machining a second part of the liquefier into a surface of the second block and bringing the first block and second block together to describe a passageway of a liquefier tube, wherein the passageway has an inlet portion with a substantially circular cross-section for receipt of a filament of material and an outlet downstream of the inlet portion, the passageway transitions from the inlet portion to a non-circular portion downstream of the inlet which has a non-circular cross-section, and the passageway has a substantially circular portion downstream of the non-circular portion.

37. A method according to claim 36, wherein the passageway comprises a substantially circular portion at or toward the outlet.

38. A method according to claim 36, wherein the non-circular portion of the passageway has a plurality of segments, each having a different cross-sectional shape or configuration and a minor dimension of a first segment and a corresponding minor dimension of a second segment are rotationally offset from one another.

Description

[0106] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0107] FIG. 1 is a schematic of an additive manufacturing system incorporating aspects of the invention;

[0108] FIG. 2 is a perspective view of a liquefier tube according to a first example;

[0109] FIG. 3 is a side view of the liquefier tube of FIG. 2;

[0110] FIG. 4 is a sectional view of the liquefier tube of FIGS. 2 and 3;

[0111] FIG. 5 is an end view of the liquefier tube of FIGS. 2 to 4.

[0112] FIG. 6 is a perspective view of a liquefier tube according to another example;

[0113] FIG. 7 is a side view of the liquefier tube of FIG. 6;

[0114] FIG. 8 is a top view of the liquefier tube of FIGS. 6 and 7;

[0115] FIG. 9 is an end view of the liquefier tube of FIGS. 6 to 8;

[0116] FIG. 10 is a perspective view of a split-block liquefier;

[0117] FIG. 11 is a perspective view of one half of the split-block liquefier of FIG. 10;

[0118] FIG. 12 is a cross-sectional view through the split block liquefier of FIG. 10;

[0119] FIG. 13 is a perspective view of a liquefier tube according to another example;

[0120] FIG. 14 is a side view of the liquefier tube of FIG. 13;

[0121] FIG. 15 is a sectional perspective view of the liquefier tube of FIGS. 13 and 14;

[0122] FIG. 16 is an end view of the liquefier tube of FIGS. 13 to 15;

[0123] FIG. 17 is a perspective view of a liquefier tube according to another example;

[0124] FIG. 18 is a side view of the liquefier tube of FIG. 17;

[0125] FIG. 19 is a top view of the liquefier tube of FIGS. 17 and 18;

[0126] FIG. 20 is a sectional perspective view of the liquefier tube of FIGS. 17 to 19; and

[0127] FIG. 21 is an end view of the liquefier tube of FIGS. 17 to 20.

[0128] Referring now to FIG. 1, there is shown a schematic of a extrusion-based additive manufacturing system 1 including a print bed 2, a gantry 3 located above the print bed 2 and an extrusion head 4 carried by, and movable along, the gantry 3. The gantry 3 is in the form of a guide rail system configured to allow movement of the extrusion head 4 in a horizontal plane within a boundary described by the print bed 2. The gantry 3 is supported above the print bed 2 by a structural frame F.

[0129] The extrusion head 4 includes a liquefier assembly having a liquefier tube 5 in this example (shown in FIGS. 2 to 5, in particular), a heating means H in the form of a heating element in this example, for heating a filament of material received within the liquefier tube 5, and a feeding mechanism 6 for advancing a filament of material along the liquefier tube 5.

[0130] Referring now to FIGS. 2 to 5, there is shown a liquefier tube 5 for use in the manufacturing system 1 of FIG. 1.

[0131] The liquefier tube 5 includes a tubular body 50 providing a passageway or flow-path (hereinafter passageway) P extending therealong and having sidewall of substantially constant wall thickness t (as shown in FIG. 5, in particular) that extends along a longitudinal axis L. The tubular body 50 is formed of metal, in particular stainless steel, in this example.

[0132] A first, upstream end of the liquefier tube 5 is provided with an inlet portion 51 of substantially circular cross-section. A second, downstream end 52 of the liquefier tube 5, opposite the inlet portion 51, is also provided with a substantially circular cross-section. The inlet portion 51 and second end 52 are located at opposite ends of the tubular body 50.

[0133] Intermediate the inlet portion 51 and second end 52 is a non-circular portion 53 having a non-circular cross-section, in the form of an obround cross-section in this example. In the present example, the non-circular portion 53 extends uninterrupted along a portion of the length of the tubular body 50, and has a substantially constant cross-sectional area. A first end portion 57, having a substantially circular cross-section extends along a portion of the length of the tubular body 50 between the inlet portion 51 and non-circular portion 53.

[0134] In the present example, the non-circular portion 53 has four discrete segments: a first segment 53a, second segment 53b downstream of first segment 53a, third segment 53c downstream of second segment 53b and fourth segment 53d downstream of third segment 53c. Each of the segments 53a:53d are arranged in series along the longitudinal axis L of tubular body 50.

[0135] The tubular body 50 is deformed by crushing to provide the non-circular portion 53. In the present example, each segment 53a:53d corresponds to a crush point/zone at which the tubular body 50 is deformed. A substantially continuous transition is provided between each segment 53a:53d and between the first end portion 57 and non-circular portion 53.

[0136] The tubular body 50 includes a continual transition when viewed downstream from the substantially circular cross section of the inlet portion 51 to the non-circular cross section of the first segment 53a. The cross sectional area at the inlet portion 51 is substantially equal to the cross sectional area of the first segment 53a in this example.

[0137] Each of the segments 53a:53d has a major dimension M1 and a minor dimension M2. When viewed downstream from the inlet portion 51 toward the second end 52, major dimension M1 increases whilst the minor dimension M2 decreases. The major dimension M1 reaches its maximum and the minor dimension M2 reaches its minimum at the fourth segment 53d.

[0138] Throughout the non-circular portion 53, the minor dimension M2 is less than the diameter of the inlet portion 51 and second end 52. Therefore, the distance from the sidewall of the tubular body 50 to the centre of the passageway P is reduced in the non-circular portion 53 when compared to the substantially circular cross-section of the inlet portion 51 and second end 52.

[0139] Downstream of the fourth segment 53d the non-circular portion 53 transitions from a non-circular cross section to a second end portion 54 having a substantially circular cross section at the downstream end 52. The second end portion 54 extends along a portion of the length of the tubular body 50 between the non-circular portion 53 and downstream end 52.

[0140] The second end 52 is provided with an extrusion tip 55 in the form of a nozzle for dispensing filament material (not shown) in a molten state. The extrusion tip 55 provides an outlet of the liquefier tube 5 and has a substantially circular passage 56 (shown in FIG. 5, in particular) extending therealong. The extrusion tip 55 is welded to the tubular body 50 at the second end 52 in this example. As shown most clearly in FIG. 5, the circular passage 56 of the extrusion tip 55 is of a smaller cross-sectional area than that of the tubular body 50.

[0141] In use, the liquefier tube 5 is received within an extrusion head 4 of an extrusion-based additive manufacturing system 1 (as shown in FIG. 1, in particular). Filament material is fed into the inlet portion 51 by a feeding mechanism 6. The substantially circular cross-section of the inlet portion 51 is configured to receive, in use, a filament of material having a circular cross section from a feeding mechanism 6.

[0142] The filament of material is advanced along the tubular body 50. Heating means H (as shown in FIG. 1, in particular), in the form of one or more heating element(s) in this example, is located within the extrusion head 4 and adjacent the liquefier tube 5. The one or more heating element(s) heat an external surface of the liquefier tube 5, which by virtue of thermal transfer, in turn heats the filament material as it is advanced.

[0143] As the filament material is advanced from the inlet portion 51 toward the non-circular portion 53, it becomes molten as a result of the heating. The cross-sectional shape of the filament material then conforms to the cross-sectional shape of the non-circular portion 53.

[0144] In the non-circular portion 53, the distance from the heating means H to the centre of the passageway P, and therefore centre of the filament material, or filament flow-path is reduced, allowing heat to more effectively reach the centre of the filament material. This allows for more effective heat transfer from the heating means H to the filament material.

[0145] Extrusion pressure is created by the feeding of filament upstream. The molten filament is extruded from the extrusion tip 55 and onto the print bed 2 (as shown more clearly in FIG. 1, in particular).

[0146] The liquefier tube 5 of FIGS. 2 to 5 is manufactured by providing a tubular body 50 having a substantially constant wall thickness t and substantially circular cross-section. The tubular body 50 is deformed or crushed at locations defined by segments 53a:53d, so as to provide an inlet portion 51 and first end portion 57 having a substantially circular cross-section for receiving a filament of material (not shown), and a non-circular portion 53, formed of segments 53a:53d, each having a non-circular cross-section. A substantially continuous transition is provided between each segment 53a:53d.

[0147] In this example, deforming or crushing the tubular body 50 is carried out by compressing the tubular body 50 at discrete points along its length using a press.

[0148] An extrusion tip 55 is connected to the tubular body 50 at the other end 52, opposite the inlet portion 51, to form an outlet for dispensing filament material in a molten state. The extrusion tip 55 is welded to the tubular body 50 in the present example.

[0149] Referring now to FIGS. 6 to 9, there is shown a liquefier tube 105 according to another example of the invention, for use in the manufacturing system 1 of FIG. 1. The liquefier tube 105 according to this example is similar to liquefier tube 5 according to the first example, wherein like features will be denoted by like references incremented by ‘100’.

[0150] The liquefier tube 105 according to this example includes a tubular body 150 providing a passageway P extending therealong and having sidewall of substantially constant wall thickness t (as shown in FIG. 9, in particular) that extends along a longitudinal axis L. As in the liquefier tube 5 according to the first example, the tubular body 150 is formed of metal, in particular stainless steel, in this example.

[0151] A first, upstream end of the liquefier tube 105 is provided with an inlet portion 151 of substantially circular cross-section. A second, downstream end 152 of the liquefier tube 105, opposite the inlet portion 151, is also provided with a substantially circular cross-section. The inlet portion 151 and second end 152 are located at opposite ends of the tubular body 150.

[0152] Intermediate the inlet portion 151 and second end 152 is a first non-circular portion 153 having a non-circular cross-section, in the form of an obround cross-section in this example. The first non-circular portion 153 is similar to non-circular portion 53 of liquefier tube 5, and extends uninterrupted along a portion of the length of the tubular body 150, and has a substantially constant cross-sectional area. A first end portion 157, having a substantially circular cross-section extends along a portion of the length of the tubular body 150 between the inlet portion 151 and first non-circular portion 153.

[0153] In this example, like the non-circular portion 53 of liquefier tube 5, the first non-circular portion 153 has four discrete segments: a first segment 153a, second segment 153b downstream of first segment 153a, third segment 153c downstream of second segment 153b and fourth segment 153d downstream of third segment 153c. Each of the segments 153a:153d are arranged in series along the longitudinal axis L of the first non-circular portion 153.

[0154] Downstream of the first non-circular portion 153, between the first non-circular portion 153 and the second end 152 is a second non-circular portion 158. The second non-circular portion 158 is similar to the first non-circular portion 153, but rotationally offset by 90 degrees.

[0155] The second non-circular portion 158 is similar to non-circular portion 53 of liquefier tube 5, and extends uninterrupted along a portion of the length of the tubular body 150, and has a substantially constant cross-sectional area. A second end portion 154, having a substantially circular cross-section extends along a portion of the length of the tubular body 150 between the second end 152 and second non-circular portion 158.

[0156] In this example, like the first non-circular portion 153, the second non-circular portion 158 has four discrete segments: a first segment 158a, second segment 158b downstream of first segment 158a, third segment 158c downstream of second segment 158b and fourth segment 158d downstream of third segment 158c. Each of the segments 158a:158d are arranged in series along the longitudinal axis L of the second non-circular portion 158.

[0157] Between the first non-circular portion 153 and second non-circular portion 158 is a transition point or zone T at which the orientation of the non-circular part of the liquefier tube 105 is rotated by 90 degrees.

[0158] The tubular body 150 is deformed by crushing to provide the first non-circular portion 153 and second non-circular portion 158. In the present example, each segment 153a:153d and 158a:158d corresponds to a crush point/zone at which the tubular body 150 is deformed. A substantially continuous transition is provided between each segment 153a:153d and 158a:158d and between the first non-circular portion 153 and second non-circular portion 158 via the transition point or zone T.

[0159] The tubular body 150 includes a continual transition when viewed downstream from the substantially circular cross section of the inlet portion 151 to the non-circular cross section of the first segment 153a. The cross sectional area at the inlet portion 51 is substantially equal to the cross sectional area of the first segment 153a in this example.

[0160] Each of the segments 153a:153d and 158a:158d has a major dimension M1 and a minor dimension M2. When viewed downstream from the inlet portion 151 toward the second end 152, within the first non-circular portion 153, major dimension M1 increases whilst the minor dimension M2 decreases. The major dimension M1 reaches its maximum and the minor dimension M2 reaches its minimum at the fourth segment 153d. The same as above applies to the second non-circular portion 158 when viewed from the transition point or zone T toward the second end 152.

[0161] In this example, the respective first segments 153a, 158a, respective second segments 153b, 158b, respective third segments 153c, 158c and respective fourth segments 153d, 158d correspond to one another in terms of cross-sectional shape, but are offset by 90 degrees. Therefore, the major dimensions M1 and minor dimensions M2 correspond to one another in each of these corresponding segments, but offset by 90 degrees.

[0162] Throughout the first non-circular portion 153 and second non-circular portion 158, the minor dimension M2 is less than the diameter of the inlet portion 151 and second end 152. Therefore, the minimum distance from the sidewall of the tubular body 150 to the centre of the passageway P is reduced in the first non-circular portion 153 and second non-circular portion 158 when compared to the substantially circular cross-section of the inlet portion 151 and second end 152.

[0163] Downstream of the fourth segment 158d the second non-circular portion 158 transitions from a non-circular cross section to the second end portion 154 having a substantially circular cross section at the downstream end 152. The second end portion 154 extends along a portion of the length of the tubular body 150 between the second non-circular portion 158 and downstream end 152.

[0164] ???As in the case of liquefier tube 5, the length of the perimeter described by the tubular body 150 in the first non-circular portion 153 and second non-circular portion 158 is greater than that at the first end portion 157 and second end portion 154. This provides a greater contact area between the tubular body 150 and filament (not shown), increasing the rate of heat transfer.

[0165] The second end 152 is provided with an extrusion tip 155 in the form of a nozzle for dispensing filament material (not shown) in a molten state. The extrusion tip 155 provides an outlet of the liquefier tube 105 and has a substantially circular passage 156 (shown in FIG. 9, in particular) extending therealong. The extrusion tip 155 is welded to the tubular body 150 at the second end 152 in this example. As shown most clearly in FIG. 9, the circular passage 156 of the extrusion tip 155 is of a smaller cross-sectional area than that of the tubular body 150.

[0166] In use, as is the case with liquefier tube 5, liquefier tube 105 is received within an extrusion head 4 of an extrusion-based additive manufacturing system 1 (as shown in FIG. 1, in particular). Filament material is fed into the inlet portion 151 by a feeding mechanism 6. The substantially circular cross-section of the inlet portion 151 is configured to receive, in use, a filament of material having a circular cross section from the feeding mechanism 6.

[0167] The filament of material is advanced along the tubular body 150. Heating means H, in the form of one or more heating element(s) in this example, is located within the extrusion head 4 and adjacent the liquefier tube 105. The one or more heating element(s) are configured to heat an external surface of the liquefier tube 105, which by virtue of thermal transfer, in turn heats the filament material as it is advanced.

[0168] As the filament material is advanced from the inlet portion 151 toward the first non-circular portion 153, it becomes molten as a result of the heating. The cross-sectional shape of the filament material then conforms to the cross-sectional shape of the first non-circular portion 153.

[0169] In the first non-circular portion 153, the distance from the heating means H to the centre of the passageway P, and therefore centre of the filament material, or filament flow-path is reduced, allowing heat to more effectively reach the centre of the filament material. This allows for more effective heat transfer.

[0170] The filament is then advanced from the first non-circular portion 153 toward the second non-circular portion 158, via the transition point or zone T. The rotational offset of the first non-circular portion 153 and second non-circular portion 158 results in mixing of the filament material, improving the heat transfer therethrough.

[0171] Extrusion pressure is created by the feeding of filament upstream. The molten filament is extruded from the extrusion tip 155 and onto the print bed 2 (as shown in FIG. 1, in particular).

[0172] In the present example, the liquefier tube 105 of FIGS. 6 to 9 is manufactured by providing a tubular body 150 having a substantially constant wall thickness t and substantially circular cross-section. The tubular body 150 is deformed or crushed in a first direction at locations defined by segments 153a:153d, so as to provide an inlet portion 151 and first end portion 157 having a substantially circular cross-section for receiving a filament of material (not shown), and a first non-circular portion 153, formed of segments 153a:153d, each having a non-circular cross-section. A substantially continuous transition is provided between each segment 153a:153d.

[0173] Downstream of the first non-circular segment 153, the tubular body 150 is deformed or crushed in a second direction, offset by 90 degrees from the first direction. The tubular body 150 is deformed or crushed in the second direction at locations defined by segments 158a:158d so as to provide transition point or zone T, and second end portion 152 having a substantially circular cross-section.

[0174] In the present example, deforming or crushing the tubular body 150 is carried out by compressing the tubular body 150 at discrete points along its length using a press.

[0175] An extrusion tip 155 is connected to the tubular body 150 at the other end 152, opposite the inlet portion 151, to form an outlet for dispensing material in a molten state. The extrusion tip 155 is welded to the tubular body 150 in the present example.

[0176] Referring now to FIGS. 10 to 12, there is shown a liquefier tube 205 according to another example of the invention, for use in the manufacturing system 1 of FIG. 1.

[0177] The liquefier tube 205 has a similar profile to liquefier tube 105, but, instead of the passageway P being described by a tubular body 150 it is described in part by a split heater block 7. The split heater block 7 has two halves 7a, 7b (as shown in FIG. 10, in particular). Each half 7a, 7b describes one half of the passageway P of liquefier tube 205.

[0178] The halves 7a, 7b are configured to be secured together to form the split heater block 7 and liquefier tube 205. The halves 7a, 7b are configured to be secured together using screws (not shown) and are each formed of metal in this example.

[0179] In the present example, the first non-circular portion 253, transition point or zone T and second non-circular portion 258 form a first element A of the liquefier tube 205 and are described by the halves 7a, 7b. The inlet portion 251 and first end portion 257 form a second element B of the liquefier tube 205, separate from the first element A. The second end 252, second end portion 254 and extrusion tip 255 form a third element C, separate from the first element A and second element B.

[0180] The second element B is secured to a threaded aperture described in first end 70 of the split heater block 7 by virtue of a threaded connection (not shown). Similarly, the third element C is secured to a threaded aperture described in the second end 71 of the split heater block 7 by virtue of a threaded connection (not shown).

[0181] The first half 7a includes a cylindrical heater cartridge 71a including electrical wires 72a extending therefrom. The second half 7b includes a temperature sensor 71b including electrical wires 72b extending therefrom. Each of the cylindrical heater cartridge 71a and temperature sensor 71b are located adjacent the first element A and extend along the entire length of the heater block 7 from the first end 70 to the second end 71 (as shown in FIG. 12, in particular).

[0182] The temperature sensor 71b and heater cartridge 71a together with a controller (not shown) allow for closed-loop feedback control of temperature via respective electrical wires 72a, 72b.

[0183] In use, the heater cartridge 71a is configured to provide heat around the entire circumference of the liquefier tube 205, in particular first element A, by virtue of conduction through the metal material of the halves 7a, 7b.

[0184] To assemble the liquefier tube 205 of FIGS. 10 to 12, each of the halves 7a, 7b are secured together using screws (not shown), in this example. The two halves 7a, 7b describe the first element A.

[0185] The second element B is screwed into the threaded aperture described in the first end 70 and the third element C is screwed into the threaded aperture described in the second end 71.

[0186] As is the case with liquefier tubes 5 and 105, liquefier tube 205 is configured to be received within an extrusion head 4 of an extrusion-based additive manufacturing system 1 (as shown in FIG. 1, in particular). The substantially circular cross-section of the inlet portion 251 is configured to receive, in use, a filament of material having a circular cross section from a feeding mechanism 6.

[0187] The filament of material is advanced along the tubular body 250. Heating means H, in the form of the cylindrical heater cartridge 71a transfers heat to the filament through the material of the first half 7a. The heater cartridge 71a heats the filament material as it is advanced along the entire length of the heater block 7. Temperature output of the heater cartridge 71a is controlled via the closed-loop feedback controller discussed above.

[0188] The effects on the filament material as it is advanced along the liquefier tube 205 is similar to that of liquefier tube 105 and, for the sake of brevity, will not be described further. In the present example, the heater block 7 begins heating the filament material upstream of the first non-circular portion 253, such that the polymer of the filament material begins liquifying prior to having to change shape.

[0189] In the present example, the liquefier tube 205 of FIGS. 10 to 12 is manufactured by providing either a pair of metallic blocks, or a single metallic block and splitting it in two, and machining the profile of the first element A into a planar face of each so as to provide halves 7a, 7b.

[0190] The second element B is formed by providing a tubular body and forming a thread along a portion thereof. The third element C is formed in a similar manner to that of the second element B, with the additional step of welding the extrusion tip 255 to a free end thereof, to from an outlet for dispensing material in a molten state.

[0191] Referring now to FIGS. 13 to 16, there is shown a liquefier tube 305 according to another example of the invention, for use in the manufacturing system 1 of FIG. 1.

[0192] The liquefier tube 305 is similar to liquefier tube 5, and like features will be denoted by like references incremented by ‘300’.

[0193] The liquefier tube 305 differs from the liquefier tube 5 in the cross-sectional profile in the non-circular portion 353.

[0194] A first, upstream end of the liquefier tube 305 is provided with an inlet portion 351 of substantially circular cross-section. A second, downstream end 352 of the liquefier tube 305, opposite the inlet portion 351, is also provided with a substantially circular cross-section. The inlet portion 351 and second end 352 are located at opposite ends of the tubular body 350.

[0195] Intermediate the inlet portion 351 and second end 352 is the non-circular portion 353 having a non-circular cross-section.

[0196] In the present example, the non-circular portion 353 has six discrete segments: a first segment 353a, second segment 353b downstream of first segment 353a, third segment 353c downstream of second segment 53b, a fourth segment 353d downstream of third segment 353c, a fifth segment 353e downstream of the fourth segment 353d and a sixth segment 353f downstream of the fifth segment 353e. Each of the segments 353a:353f are arranged in series along the longitudinal axis L of tubular body 350.

[0197] Moving toward the second end 352 from the inlet portion 351, the cross-sectional profile of the tubular body 350 is progressively deformed such that it has a cross or cruciform shape at the fourth segment 353d. Moving toward the second end 352 from the fourth segment 353d, the cross-sectional profile of the tubular body has a gradual or continual transition toward a substantially circular profile at the second end 352 and second end portion 354. In the non-circular portion 353, the distance from the heating means H (as shown in FIG. 1, in particular) to the centre of the passageway P, and therefore centre of the filament material, or filament flow-path is reduced, allowing heat to more effectively reach the centre of the filament material.

[0198] Further, the cross or cruciform profile provides a lower flow area (shown more clearly in FIG. 16, in particular), allowing for more effective heat transfer into a filament material being conveyed along the passageway P. The restriction in flow area, in particular in the fourth segment 353d, also manipulates the filament material, promoting mixing.

[0199] The advancement of filament material, in use, is similar to that described above in relation to liquefier 5, 105 and 205 and, for the sake of brevity, will not be described further.

[0200] In the present example, the liquefier tube 305 of FIGS. 13 to 16 is manufactured by providing a tubular body 350 having a substantially constant wall thickness t and substantially circular cross-section. The tubular body 350 is deformed or crushed at locations defined by segments 353a:353f, so as to provide an inlet portion 351 and first end portion 357 having a substantially circular cross-section for receiving a filament of material (not shown), and a non-circular portion 353, formed of segments 353a:353f, each having a non-circular cross-section. A substantially continuous transition is provided between each segment 353a:353f.

[0201] In the present example, deforming or crushing the tubular body 350 is carried out by compressing the tubular body 50 at discrete points along its length using a press. In particular, in the present example, the tubular body 350 is deformed using a punch and die, or press brake.

[0202] Referring now to FIGS. 17 to 21, there is shown a liquefier tube 405 according to another example of the invention, for use in the manufacturing system 1 of FIG. 1.

[0203] The liquefier tube 405 is similar to liquefier tube 5, 105, 205 and 305 and like features will be denoted by like references incremented by ‘400’.

[0204] The liquefier tube 405 differs from the above-described liquefier tubes in that the flow path or passageway P described thereby has a constant hydraulic diameter D.sub.H. The hydraulic diameter is defined by the following equation:

[00002]$D_H=\raisebox{1ex}{$4A$}\!\left/ \!\raisebox{-1ex}{$P$}\right.$

[0205] Where D.sub.H is the hydraulic diameter, A is the flow area and P is the perimeter described by the tubular body 450.

[0206] Hydraulic diameter D.sub.H allows pipework of non-circular cross-section to be approximated as circular for the purposes of pressure drop and fluid flow rate calculations. Having a liquefier tube 405 having a constant hydraulic diameter D.sub.H provides, in use, a substantially constant pressure as a filament material is being advanced.

[0207] Therefore, in the case of liquefier tube 405, the change in cross-sectional shape in the non-circular portion 453 allows for more effective heat transfer to a filament material as is being advanced, but whilst without increasing the pressure applied to generate a given flow rate.

[0208] A first, upstream end of the liquefier tube 405 is provided with an inlet portion 451 of substantially circular cross-section. A second, downstream end 452 of the liquefier tube 405, opposite the inlet portion 451, is also provided with a substantially circular cross-section. The inlet portion 451 and second end 452 are located at opposite ends of the tubular body 450.

[0209] Intermediate the inlet portion 451 and second end 452 is the non-circular portion 453 having a non-circular cross-section. The first end portion 457, second end portion 454 and non-circular portion 453 have a constant hydraulic diameter D.sub.H.

[0210] In the present example, the non-circular portion 453 has four discrete segments: a first segment 453a, second segment 453b downstream of first segment 453a, third segment 453c downstream of second segment 453b and a fourth segment 453d downstream of third segment 453c. Each of the segments 453a:453d are arranged in series along the longitudinal axis L of tubular body 450.

[0211] The tubular body 450 includes a continual transition when viewed downstream from the substantially circular cross section of the inlet portion 451 to the non-circular cross section of the first segment 453a. The cross sectional area at the inlet portion 451 is substantially equal to the cross sectional area of the first segment 453a in this example.

[0212] Like liquefier tube 5, each of the segments 453a:453d has a major dimension M1 and a minor dimension M2. When viewed downstream from the inlet portion 451 toward the second end 452, major dimension M1 increases whilst the minor dimension M2 decreases. The major dimension M1 reaches its maximum and the minor dimension M2 reaches its minimum at the fourth segment 453d.

[0213] Throughout the non-circular portion 453, the minor dimension M2 is less than the diameter of the inlet portion 451 and second end 452. Therefore, the distance from the sidewall of the tubular body 450 to the centre of the passageway P is reduced in the non-circular portion 453 when compared to the substantially circular cross-section of the inlet portion 451 and second end 452.

[0214] Downstream of the fourth segment 453d the non-circular portion 453 transitions sharply from a non-circular cross section to the second end portion 454 having a substantially circular cross section at the downstream end 452.

[0215] In the present example, the liquefier tube 405 of FIGS. 17 to 21 may be manufactured in a similar manner to that of liquefier tube 205 described above, i.e. by providing either a pair of metallic blocks, or a single metallic block and splitting it in two, and machining the profile of one half of the passageway P into a planar face of each so as to provide halves that, when brought together, describe passageway P.

[0216] As an alternative, the liquefier tube 405 may be manufactured by providing a sheet of metal and carrying out a hydroforming process so as to form one half of the tubular body 450. A pair of halves are then attached to one another so as to form the tubular body 450.

[0217] As a further alternative, the liquefier tube 405 may be manufactured by carrying out a hydroforming process on a tubular body 450. Deforming the tubular body 450 by hydroforming may comprise placing the tubular body 450 between a pair of dies and injecting fluid under pressure into passageway P. The fluid under pressure causes the tubular body 450 to deform such that it conforms to a profile described by the forming tool or pair of dies and forms non-circular portion 453.

[0218] An extrusion tip 455 is connected to the tubular body 450 at the other end 452, opposite the inlet portion 451, to form an outlet for dispensing material in a molten state. The extrusion tip 455 is welded to the tubular body 450 in the present example.

[0219] It will be appreciated by those skilled in the art that several variations to the aforementioned examples are envisaged without departing from the scope of the invention. For example, the non-circular portion of the tubular body need not have an obround cross-section. Instead, the non-circular portion may have any other suitable non-circular cross section, for example, rectangular, star-shaped, elliptical, square, oval, regular polygonal, irregular polygonal, simple convex polygonal or simple concave polygonal..

[0220] Although the tubular member is described as being formed of metal, in particular stainless steel, this need not be the case. Instead, the tubular member may be made of brass, copper, tungsten, titanium, molybdenum, beryllium copper or any other suitable metal or alloy.

[0221] Alternatively, the tubular member may be made of a polymeric material, e.g. a thermally conductive polymeric material.

[0222] Although the transition or change from the substantially circular inlet portion to the non-circular portion is described as being continual, the skilled person will appreciate that this need not be the case. Instead, the transition may comprise a staged, discretised and/or stepped transition.

[0223] In examples, the extrusion tip or nozzle may be removably connected to the liquefier tube or tubular body. Instead of being welded, as described above, the extrusion tip or nozzle may be brazed to the liquefier tube or tubular body.

[0224] The non-circular portion 53 is described as having a taper along a portion of the length of the tubular body 50. Alternatively, the non-circular portion of the tubular body may comprise a plurality of segments or sections. Each of the plurality of segments or sections may comprise a deformed or crushed segment of the tubular body. Each of the plurality of segments or sections may be arranged, e.g. in series, along the length of, or principal axis of, the liquefier tube or tubular body. Each of the plurality of segments or sections may be arranged along a longitudinal axis of the liquefier tube or tubular body.

[0225] Each of the plurality of segments or sections, hereinafter segments, may have a different cross-sectional shape, configuration or cross-sectional profile, e.g. from one another. One, e.g. a first, of the plurality of segments may have a different cross-sectional shape, configuration or cross-sectional profile from another, e.g. a second, of the plurality of segments.

[0226] In some examples, the first segment and the second segment, e.g. their major and/or minor dimensions, are rotationally offset or skewed from one another. The first segment and the second segment may be skewed or twisted from, or relative to, one another. The first segment and second segment may comprise a skew angle described therebetween. The first segment may comprise a portion of the tubular body deformed or crushed in a direction that is skewed or rotationally offset relative to a direction in which the second segment is deformed or crushed.

[0227] Corresponding minor and/or major dimensions of the first segment and second segment may be rotationally offset or skewed from one another.

[0228] Although the non-circular portion 53 is described as being uninterrupted, this need not be the case. Instead, the tubular body 50 may have a substantially circular portion intermediate two or more segments of the non-circular portion.

[0229] It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.