Liquefier assembly

Abstract

The invention relates to a liquefier assembly (100) for an additive manufacturing system, which includes a first, high temperature part (1), a second, low temperature part (2) and a heat break tube (3) joining the first and second parts (1, 2) such that there is a gap (G) therebetween. The liquefier assembly (100) also includes bracing means (4) within the gap (G) but spanning only part of the gap (G). The assembly (100) is configured such that a bending moment applied, in use, to the heat break tube (3) causes the first and second parts (1, 2) to brace against one another via the bracing means (4), thereby to limit bending of the heat break tube (3).

Description

[0001] LIQUEFIER ASSEMBLY

[0002] This invention relates generally to additive manufacturing systems for producing three- dimensional (3D) parts and particularly to liquefier assemblies for such systems. More specifically, although not exclusively, this invention relates to such a liquefier assembly having a replaceable nozzle.

[0003] Additive manufacturing, also called 3D printing, is a process in which a part is made by adding material, rather than subtracting material as in traditional machining. A part is manufactured from a digital model using an additive manufacturing system, commonly referred to as a 3D printer. A typical approach is to slice the digital model into a series of layers, which are used to create two-dimensional path data, and to transmit the data to a 3D printer which manufactures the part in an additive build style. There several different methods of depositing the layers, such as stereolithography, ink jetting, selective laser sintering, powder / binder jetting, electron-beam melting and material extrusion.

[0004] In a typical extrusion-based additive manufacturing system, such as a fused deposition modelling system, a part may be formed by extruding a viscous, molten thermoplastic material from a distribution head along predetermined paths at a controlled rate. The head includes a liquefier, which receives thermoplastic material, normally in the form of a filament. A drive mechanism engages the filament and feeds it into the liquefier. The filament is fed through the liquefier, where it melts to produce the flow of molten material, and into a nozzle for depositing the molten material onto a substrate. The molten material is deposited along the predetermined paths onto the substrate, where it fuses to previously deposited material and solidifies as it cools, gradually building the part in layers.

[0005] Conventional liquefiers include a high temperature part, typically a heater and nozzle, a low temperature part, typically a heat sink, and a heat break between the two for isolating the low temperature part from the high temperature part. The heat break is normally a tube with a relatively thin wall, and so any side impact experienced by the high temperature part will damage the heat break.

[0006] It would therefore be advantageous to provide a means of protecting the heat break.

[0007] Accordingly, a first aspect provides a liquefier assembly, e.g. for an additive manufacturing system, the assembly comprising: a first, high temperature part; a second, low temperature part; a heat break or heat break tube joining the first and second parts and a bracing means for protecting the heat break.

[0008] The heat break or heat break tube may join the first and second parts such that there is a gap therebetween. The bracing means may be within or located within the gap. The bracing means may span part of the gap, e.g. only part of the gap or less than the entire gap. The assembly may be configured such that a bending moment applied, in use, to the heat break tube causes the first and second parts to brace against the bracing means, or in some cases brace against one another via the bracing means, thereby to limit bending of the heat break tube.

[0009] Another aspect provides a liquefier assembly for an additive manufacturing system, the assembly comprising: a first, high temperature part; a second, low temperature part; a heat break tube joining the first and second parts such that there is a gap therebetween; and bracing means within the gap but spanning only part of the gap; wherein the assembly is configured such that a bending moment applied, in use, to the heat break tube causes the first and second parts to brace against one another via the bracing means, thereby to limit bending of the heat break tube.

[0010] The bracing means may project from one of the parts toward the other part. In some cases, the bracing means may project from the first part toward the second part, or toward a bracing surface of the second part which may face the first part. In some cases, the bracing means may project from the second part toward the first part, or toward a bracing surface of the first part which may face the second part.

[0011] The bracing means may comprise one or more bracing elements. The or each bracing element(s) may at least partially surround the heat break tube. The one or more bracing elements may comprise at least two bracing elements, which may be on different sides of the heat break tube.

[0012] The one or more bracing elements may comprise three or more bracing elements. The bracing elements may be spaced equally about the heat break tube. In some cases, the one or more bracing elements comprises four or more bracing elements. The or each bracing element may take any shape. In some cases, the or each or at least one bracing element may comprise a pin, cylindrical member, block, cuboid, nodule, ring or any other form. The or each or at least one bracing element may comprise a bracing ring. The or each bracing element may be continuous or segmented.

[0013] The bracing ring may be continuous or segmented. The bracing ring may include a plurality of spaced bracing elements. The bracing ring may be segmented and includes a plurality of spaced bracing elements. The plurality of spaced bracing elements of the bracing ring may comprise any suitable shape, for example part circular or part-cylindrical.

[0014] In some cases, the one or more bracing elements comprise a plurality of spaced bracing elements together describing a bracing ring. In such cases, the bracing ring, e.g. segmented bracing ring, may comprise a plurality of bracing elements in the form of pins, cylindrical members, blocks, cuboids, nodules, or any other forms which together describe or form the bracing ring.

[0015] The or each or at least one bracing element may be integral with one of the parts. The or each or at least one bracing element may be connected to one of the parts. The or each or at least one bracing element may be a separate component that is mounted or connected to one of the parts. The or each or at least one bracing element may project from one of the parts, e.g. toward the other part.

[0016] The first part may comprise a heater block. The first part may comprise a heater, e.g. a nozzle heater. The first part may comprise a nozzle, e.g. a heated nozzle. The first part or nozzle may comprise a nozzle tip. The nozzle or nozzle tip may be mounted or connected or otherwise associated with the heater. In some cases, the nozzle may comprise heating means. The heater may incorporate, or be incorporated in, the nozzle.

[0017] The first part may comprise or describe a filament passage. The filament passage may be described at least in part by the heater block or heater. The filament passage may be described at least in part by the nozzle. In some cases, the filament passage is described in part by the heater block or heater and in part by the nozzle, for example where the nozzle is connected to the heater block or heater. In other cases, e.g. where the nozzle includes heating means, the filament passage of the first part may be described entirely or mostly by the nozzle. The second part may comprise a heat exchange body, for example a heat sink. The heat sink may comprise one or more fins, e.g. cooling fins. The second part may comprise or describe a filament passage.

[0018] The heat break tube may comprise or describe a filament passage. The filament passage of the heat break tube may join the filament passage of the first and second parts.

[0019] Another aspect provides a liquefier assembly, e.g. for an additive manufacturing system, the assembly comprising a first, high temperature part, a heat break tube connected to the first part and bracing means projecting from the first part.

[0020] The heat break tube may comprise a connection means, e.g. for connection with a second, low temperature part such that there is a gap between the first and second parts. The bracing means may project from the first part so as to be located within the gap, e.g. when the heat break tube is connected to the second part. The bracing means may project from the first part so as to span only part of the gap, e.g. when the heat break tube is connected to the second part.

[0021] The assembly may be configured such that a bending moment applied, in use, to the heat break tube causes the second part to brace against the bracing means, thereby to limit bending of the heat break tube.

[0022] Another aspect provides a liquefier assembly for an additive manufacturing system, the assembly comprising: a first, high temperature part; a heat break tube connected to the first part and having a connection means for connection with a second, low temperature part such that there is a gap between the first and second parts; and bracing means projecting from the first part so as to be located within the gap, but span only part of the gap, when the heat break tube is connected to the second part; wherein the assembly is configured such that a bending moment applied, in use, to the heat break tube causes the second part to brace against the bracing means, thereby to limit bending of the heat break tube.

[0023] The heat break tube may comprise an external thread, e.g. for cooperation with a corresponding internal thread of the second part. The heat break tube may comprise a stop, e.g. for cooperation with a corresponding stop of the second part to provide the gap. In some cases, the heat break tube is press-fit into the or a filament passage of the first part. In other cases, the heat break tube is integral with the first part. The high temperature part and the heat break tube may together form a hot side sub-assembly. The assembly may comprise a hot side sub-assembly that includes the high temperature part and the heat break tube.

[0024] The heat break tube may comprise a first, connector part, which may comprise the thread and / or the stop. The heat break tube may comprise a second, heat break part, e.g. onto which the first part is press-fit. Alternatively, the first and second parts may be connected in some other way, such as brazed or welded. In yet other cases, the first and second parts may be integral and / or formed of a single piece of material.

[0025] The bracing means may be configured to inhibit bending of the heat break tube beyond a predetermined point or limit, e.g. its elastic limit. In some examples, the bracing means may be configured to inhibit bending of the heat break tube beyond 50% or 75% of its elastic limit.

[0026] Another aspect provides nozzle for a liquefier assembly, e.g. of an additive manufacturing system. Another aspect provides nozzle heater for a liquefier assembly, e.g. of an additive manufacturing system. Another aspect provides heater block for a liquefier assembly, e.g. of an additive manufacturing system.

[0027] The nozzle, nozzle heater or heater block may comprise a body. The body may comprise a filament passage, e.g. described therein. The nozzle, nozzle heater, heater block or body may comprise one or more bracing elements. The bracing element(s) may project from the body, e.g. in a direction parallel to the filament passage.

[0028] The body may be configured to be joined to a low temperature part by a heat break tube such that there is a gap therebetween with the bracing element(s) within the gap but spanning only part of the gap such that a bending moment applied, in use, to the heat break tube causes the high temperature part and the low temperature to brace against the bracing means, thereby to limit bending of the heat break tube. Another aspect of the invention provides a nozzle, nozzle heater or heater block for a liquefier assembly, e.g. of an additive manufacturing system, the nozzle, nozzle heater or heater block comprising a body with a filament passage described therein and one or more bracing elements projecting from the body in a direction parallel to the filament passage, wherein the body is configured to be joined to a low temperature part by a heat break tube such that there is a gap therebetween with the bracing element(s) within the gap but spanning only part of the gap such that a bending moment applied, in use, to the heat break tube causes the high temperature part and the low temperature to brace against the bracing means, thereby to limit bending of the heat break tube.

[0029] For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention.

[0030] Another aspect of the invention provides a computer program element comprising and / or describing and / or defining a three-dimensional design, e.g. of the liquefier assembly, high temperature part, low temperature part or heat break tube described above or an embodiment thereof. The three-dimensional design may be for use with a simulation means or an additive or subtractive manufacturing means, system or device.

[0031] The computer program element may be for causing, or operable or configured to cause, an additive or subtractive manufacturing means, system or device to manufacture the liquefier assembly, high temperature part, low temperature part or heat break tube described above or an embodiment thereof. The computer program element may comprise computer readable program code means for causing an additive or subtractive manufacturing means, system or device to execute a procedure to manufacture the liquefier assembly, high temperature part, low temperature part or heat break tube described above or an embodiment thereof.

[0032] A yet further aspect of the invention provides the computer program element embodied on a computer readable medium.

[0033] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible.

[0034] For the avoidance of doubt, the terms “may”, “and / or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so- described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed.

[0035] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0036] Figure 1 is a front view of a liquefier assembly according to one example;

[0037] Figure 2 is a perspective view of the liquefier assembly of Figure 1 ;

[0038] Figure 3 is a perspective view of the low temperature part of the liquefier assembly of Figures 1 and 2;

[0039] Figure 4 is a perspective view of the high temperature part and heat break tube of the liquefier assembly of Figures 1 and 2; and

[0040] Figure 5 is an exploded view of the liquefier assembly of Figures 1 and 2.

[0041] Referring now to Figures 1 to 5, there is shown a liquefier assembly 100 for an additive manufacturing system. The assembly 100 includes a first, high temperature part 1 , a second, low temperature part 2 and a heat break tube 3 joining the first and second parts 1 , such that there is a gap G therebetween. The assembly 100 also includes bracing means 4 within the gap G but spanning only part of the gap G.

[0042] In this example, the high temperature part 1 includes a heater block 10 with integral heating means (not shown) and a nozzle tip 11 press-fit into a body 12 of the heater block 10. The body 12 includes a filament passage 13 described therein and the bracing means 4 projects from the body 12 in a direction parallel to the filament passage 13. The nozzle tip 11 is generally cylindrical with a tapered end 14, a torpedo-shaped core 15 on its opposite side and a plurality of holes 16 that converge toward an outlet hole 17.

[0043] The low temperature part 2 includes a heat sink 20 in this example, with a filament passage 21 along its axial length and a plurality of cooling fins 22 projecting radially outwardly from the heat sink 20. The heat sink 20 also includes a connector 23 at one of its ends for connection with a filament feed mechanism (not shown) and a recess 24 at its opposite end whose base forms a bracing surface 25. In this example, the heat sink 20 includes a radial air passage cutout 27 for allowing air to be introduced into the gap G for cooling an exposed portion of the heat break tube 3.

[0044] The heat break tube 3 includes a first, connector part 30 and a second, heat break part 31 onto which the first part 30 is press-fit, although both parts could be integral and formed as a single body. The connector part 30 includes an external thread 32 along part of its length and a radial flange 33 at the end that receives the heat break part 31. The heat break part 31 is in the form of a tube having a substantially constant wall thickness. The heat break tube 3 describes a filament passage 34 along its length.

[0045] The heat break part 31 of the heat break tube 3 is press-fit into the filament passage 13 of the body 12 of the heater block 10, such that the heat break tube 3 projects from the heater block 10 with the external thread 32 of the connector part 30 adjacent its free end. As such, the high temperature part 1 and the heat break tube 3 together form a hot side subassembly 5.

[0046] In this example, the bracing means 4 includes four bracing elements, or bracing pins 40. The bracing means 4 may take different forms and / or include a different number of bracing elements, which may also have different shapes as explained above. The bracing pins 40 are press-fit into corresponding blind holes (not shown) in the body 12 of the heater block 10. However, they may instead be formed integrally with the heater block 10 or be secured thereto in any number of ways, such as brazing or welding.

[0047] The hot side sub-assembly 5 is removably connectable to the low temperature part 2 by inserting and rotating the connector part 30 of the heat break tube 3 to engage the external thread 32 with an internal thread (not shown) in the filament passage 21 of the heat sink 20. Continued rotation draws the hot side sub-assembly 5 toward the low temperature part 2 until the radial flange 33 is received within the ring 26 in the recess 24 of the heat sink 20 until it engages the base of the recess 24. As such, the radial flange 33 acts as a stop to locate the hot side sub-assembly 5 relative to the low temperature part 2, thereby creating a predetermined gap G.

[0048] In this, assembled condition, the filament passages 13, 21 , 34 are all aligned and communicate with one another such that a filament fed, in use, into the filament passage 21 of the heat sink 20 passes through the filament passage 34 of the heat break 3 and into the filament passage 13 of the heater block 10, where it is melted and extruded out of the outlet 17 of the nozzle tip 11. Moreover, the bracing pins 40 project from the body 12 of the heater block 10 toward the bracing surface 25 of the heat sink 20, but are spaced therefrom by a clearance C. As a result, the bracing pins 40 project into the gap G but span only part of it.

[0049] In use, the assembly 100 is configured such that a bending moment applied to the heat break tube 3, for example by a lateral impact experienced by the body 12 of the heater block 10, causes the first and second parts 1 , 2 to brace against one another via the bracing means 4, specifically the bracing pins 40. This limits bending of the heat break tube 3, specifically bending of the heat break part 31 which is the weakest part of the heat break tube 3.

[0050] Advantageously, the clearance C is selected so that the bracing means 4 inhibits bending of the heat break tube 3, specifically the heat break part 31 , beyond its elastic limit. In fact, in this example the clearance C is selected to limit the bending to 80% of the elastic limit of the heat break part 31 , although other configurations are envisaged without departing from the scope of the invention.

[0051] The skilled person will appreciate that the distribution of the bracing pins 40 ensures that bending in any direction along a plane perpendicular to the filament passage is inhibited. The bracing means 4 may include only three bracing pins 40 whilst preserving this aspect, although four or more is preferred. Alternatively, the bracing means 4 may include elements having different shapes, as outlined above. It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention.

Claims

CLAIMS1 . A liquefier assembly for an additive manufacturing system, the assembly comprising: a first, high temperature part; a second, low temperature part; a heat break tube joining the first and second parts such that there is a gap therebetween; and bracing means within the gap but spanning only part of the gap; wherein the assembly is configured such that a bending moment applied, in use, to the heat break tube causes the first and second parts to brace against one another via the bracing means, thereby to limit bending of the heat break tube.

2. The liquefier assembly of claim 1 , wherein the bracing means projects from one of the parts toward the other part.

3. The liquefier assembly of claim 2, wherein the bracing means projects from the first part toward a bracing surface of the second part which faces the first part.

4. The liquefier assembly of any preceding claim, wherein the bracing means comprises one or more bracing elements at least partially surrounding the heat break tube.

5. The liquefier assembly of claim 4, wherein the one or more bracing elements comprises at least two bracing elements on different sides of the heat break tube.

6. The liquefier assembly of claim 4 or claim 5, wherein the one or more bracing elements project from the body in a direction parallel to the heat break tube.

7. The liquefier of any one of claims 4 to 6, wherein the one or more bracing elements comprises three or more bracing elements spaced equally about the heat break tube.

8. The liquefier assembly of any one of claims 4 to 7, wherein the or each bracing element comprises a pin integral with or connected to and projecting from one of the parts toward the other part.

9. The liquefier assembly of any one of claims 4 to 7, wherein the one or more bracing elements comprises a bracing ring.

10. The liquefier assembly of claim 9, wherein the bracing ring is segmented and includes a plurality of spaced bracing elements.11 . The liquefier assembly of any preceding claim, wherein the second part comprises a heat sink and the first part comprises a nozzle or nozzle heater or heater block.

12. A liquefier assembly for an additive manufacturing system, the assembly comprising: a first, high temperature part; a heat break tube connected to the first part and having a connection means for connection with a second, low temperature part such that there is a gap between the first and second parts; and bracing means projecting from the first part so as to be located within the gap, but span only part of the gap, when the heat break tube is connected to the second part; wherein the assembly is configured such that a bending moment applied, in use, to the heat break tube causes the second part to brace against the bracing means, thereby to limit bending of the heat break tube.

13. The liquefier assembly of any preceding claim, wherein the heat break tube comprises an external thread for cooperation with a corresponding internal thread of the second part and a stop for cooperation with a corresponding stop of the second part to provide the gap.

14. The liquefier assembly of claim 13, wherein the heat break tube is press-fit into the or a filament passage of the first part.

15. The liquefier assembly of claim 13 or claim 14, wherein the heat break tube comprises a first, connector part and a second, heat break part onto which the first part is press- fit, the first part comprising the thread.

16. The liquefier assembly of any preceding claim, wherein the bracing means is configured to inhibit bending of the heat break tube beyond its elastic limit.

17. A nozzle, nozzle heater or heater block for a liquefier assembly of an additive manufacturing system, the nozzle, nozzle heater or heater block comprising a body with a filament passage described therein and one or more bracing elements projecting from the body in a direction parallel to the filament passage, wherein the body is configured to be joined to a low temperature part by a heat break tube such that there is a gap therebetween with the bracing element(s) within the gap but spanning only part of the gap such that a bending moment applied, in use, to the heat break tube causes the high temperature part and the low temperature to brace against the bracing means, thereby to limit bending of the heat break tube.

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