GB2601021A

GB2601021A - Nozzle

Info

Publication number: GB2601021A
Application number: GB2107196.4A
Authority: GB
Inventors: Sherlock Mike; Roberts Dylan; Yonge Roy; Theobold Sam; Everitt Andy
Original assignee: E3D Online Ltd
Current assignee: E3D Online Ltd
Priority date: 2021-05-19
Filing date: 2021-05-19
Publication date: 2022-05-18
Anticipated expiration: 2041-05-19
Also published as: GB202107196D0; GB2601021B

Abstract

A liquefier nozzle 1 for an additive manufacturing system, such as fused deposition modelling, includes a body 2 formed of a first, thermally conductive material and an insert 3 formed of a second, wear resistant material. The body has a connecting feature 20 for connecting the nozzle to a heater of a liquefier assembly, a receptacle 26 having a substantially constant cross-section extending from a mouth 23 at a downstream end of the body and a filament passageway 25 extending from an upstream end to the receptacle and having a smaller diameter than the receptacle. The insert has a filament passageway 35 extending from an upstream end of the insert to a smaller diameter outlet 36 at a downstream end of the insert with a tapered transition 37. The insert is press-fit into an interference engagement within the receptacle of the body. Preferably, the first material comprises a copper alloy and the second material comprises steel. A coating may be applied to the downstream end of the insert; the coating may be harder than each of the first and second material, the coating may comprise a modified chemical composition to reduce adhesion of molten plastic thereto, the coating may comprise a diamond-like carbon coating. A method of manufacturing a liquefier nozzle comprising press fitting the insert into the body is further provided.

Description

NOZZLE

This invention relates generally to additive manufacturing systems for producing three-dimensional (3D) parts and particularly to nozzles for such systems. More specifically, although not exclusively, this invention relates to a liquefier nozzle with multiple parts.

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.

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.

It is known to provide liquefier assemblies for extrusion-based additive manufacturing systems, in which the nozzle includes a wear-resistant insert. For example, US 2017/232674 Al discloses a liquefier nozzle including a thermally conductive body with a throat and tip having a predetermined hardness.

This invention seeks to provide an improved liquefier nozzle, preferably one that mitigates one or more issues associated with known designs.

Accordingly, a first aspect of the invention provides a liquefier nozzle for an additive manufacturing system, the nozzle comprising a body formed of a first material and an insert formed of a second material, wherein the insert is received, for example releasably received, within the body.

The provision of an insert that is able to be separated from the body enables multiple materials to be used, without compromising on the recyclability of the nozzle.

The first material may be thermally conductive, for example more thermally conductive than the second material. The second material may be wear resistant, for example more wear resistant than the first material. The coefficient of thermal expansion of the first material io may be more, for example at least 20% more or at least 30% more, than that of the second material. The coefficient of thermal expansion of the first material may be between 20%50% more, such as 30%-40% more, than that of the second material. The insert may be press-fit into an interference engagement within the body. This enables a simple, yet effective means of securing the insert within the body, with the added benefit of enabling is the insert to be separated more readily from the body.

The body may have a connecting feature, which may be at or adjacent a first, upstream end of the body, e.g. for connecting the nozzle to a heater of a liquefier assembly. The body may have a receptacle, which may extend from a second, downstream end of the body.

The body may have a filament passageway, which may extend from the first end of the body, for example to the receptacle. The filament passageway may have a smaller diameter than the receptacle.

The insert may have a filament passageway, which may extend from an upstream end of the insert. The insert may have an outlet, which may be at a downstream end of the insert.

The outlet may have a smaller diameter than the filament passageway of the insert. The insert may have a transition, which be tapered or conical and/or which may join the filament passageway to the outlet. The insert may be press-fit into an interference engagement within the receptacle of the body.

Another aspect of the invention provides a liquefier nozzle for an additive manufacturing system, the nozzle comprising a body formed of a first, thermally conductive material and an insert formed of a second, wear resistant material, the body having a connecting feature at or adjacent a first, upstream end of the body for connecting the nozzle to a heater of a liquefier assembly, a receptacle extending from a second, downstream end of the body and a filament passageway extending from the first end of the body to the receptacle and having a smaller diameter than the receptacle, the insert having a filament passageway extending from an upstream end of the insert, an outlet at a downstream end of the insert, which has a smaller diameter than the filament passageway of the insert, and a tapered or conical transition joining the filament passageway to the outlet, wherein the insert is press-fit into an interference engagement within the receptacle of the body.

The interference engagement between the insert and the body may comprise, provide or be able to withstand a push-out force of at least 80 N, preferably at least 100 N, more io preferably at least 120 N and most preferably at least 150 N, e.g. when the temperature of the nozzle is 300°C or 350°C. However, it is preferable that the nozzle comprises, provides or is able to withstand these push-out forces (i.e. at least 80 N, preferably at least 100 N, more preferably at least 120 N and most preferably at least 150 N) when the nozzle temperature is 400°C or even 450°C.

The first material preferably has a yield strength of at least 250 MPa, preferably at least 300 MPa and more preferably at least 350 MPa. The first material may have a thermal conductivity that is higher than that of the second material. The first material may have a thermal conductivity of at least 100 W/m K, preferably at least 150 W/m K, more preferably at least 200 W/m K, yet more preferably at least 300 W/m K. The first material may have a coefficient of thermal expansion of at least 10 pm/m K, preferably at least 13 pm/m K and more preferably at least 15 pm/m K. The first material may comprise copper. The first material is preferably a copper alloy, such as chromium zirconium copper. The first material or its composition may comprise mainly copper, for example at least 95% copper, preferably at least 97% copper, for example at least 98% copper. The first material or its composition may comprise up to 2.0% chromium, such as up to 1.5% chromium, for example between 0.5%-1.5% chromium. The first material or its composition may comprise up to 0.30% zirconium, such as up to 0.25% zirconium, for example between 0.05%-0.25% zirconium. The balance of the composition of the first material may be copper, e.g. with the exception of impurities. The applicants have found that such an alloy composition provides a synergistic balance between strength, to provide the requisite push-out force, and thermal conductivity.

The second material may comprise steel. The steel is preferably a machinable steel. The steel is preferably more machinable than tool steel. The second material may have a hardness of at least 40 HRC, preferably at least 50 HRC and most preferably at least 60 HRC. The second material may have a thermal conductivity of between 40 W/m K and 50 W/m K. The second material or its composition may comprise 3.0% chromium or less, preferably 2.0% or less. For example, the second material or its composition may comprise or consist of 1.00%-1.60% chromium. The second material or its composition may comprise or consist to of 0.20% vanadium or less, preferably 0.10% or less. For example, the second material or its composition may comprise or consist of 0.05% vanadium or less. The second material or its composition may comprise or consist of 0.50% molybdenum or less, preferably 0.20% or less. For example, the second material or its composition may comprise or consist of 0.15% molybdenum or less. The second material may be, or have a composition that is, substantially free of Tungsten, e.g. with the exception of impurities.

The second material or its composition may comprise or consist of 1.50% carbon or less, preferably 0.90%-1.20% carbon. The second material or its composition may comprise or consist of 0.40% silicon or less, preferably 0.10%-0.35% silicon. The second material or its composition may comprise or consist of 1.00% manganese or less, preferably 0.30%- 0.75% manganese. The second material or its composition may comprise or consist of up to 0.10% of sulphur, preferably up to 0.05% of sulphur. The second material or its composition may comprise or consist of up to 0.1% phosphorus, preferably up to 0.05% phosphorus. The second material or its composition may comprise or consist of up to 1.00% nickel, preferably up to 0.40% nickel.

The receptacle may have a mouth, for example at the second end of the body. The receptacle may have a substantially constant cross-section, e.g. from the mouth to the filament passageway. The receptacle may have a substantially constant cross-section extending from a mouth at the second, downstream end of the body. The receptacle may have a base. The body may comprise a step, e.g. an internal step. The step may join the receptacle and the filament passageway. The step may comprise a radial step. The step may describe a plane, which may be substantially perpendicular to the filament passageway and/or the receptacle or its axis or their axes.

The insert and the second end of the body describe, e.g. together describe, a substantially contiguous surface. In some examples, the substantially contiguous surface is substantially perpendicular to the filament passageway and/or the receptacle or its axis or their axes. The insert may comprises a tapered or conical outer surface, for example between the substantially contiguous surface and the outlet. Thus, the insert may describe a protruding portion of the nozzle. The insert may describe the outer surface of the nozzle that is configured to contact, in use, deposited material.

Thus, the geometry of the insert may be such that the body is substantially protected from io exposure to deposited material, thereby reducing wear to the body. This enables the body to be formed of a material selected for its thermal performance, without the need for any substantial wear resistant properties.

In other examples, the substantially contiguous surface may be tapered The insert may comprise a tapered or conical tip, which may comprise or describe the tapered or conical outer surface. The transition may be within the tapered or conical tip. The angle of the transition may be similar to that of the outer surface of the tapered or conical tip, e.g. such that a substantially constant thickness is described therebetween.

This, substantially constant thickness has been found to balance strength with thermal mass, given the lower thermal conductivity of the insert.

The nozzle or body may comprise a head, which may describe the second end of the body.

The head may be shaped and/or configured to engage and/or be driven, in use, by a tool, for example to connect the connecting feature of the nozzle to a heater of a liquefier assembly. The connecting feature of the body may comprise one or more threads, e.g. external threads. The threads of the body may be configured to engage, in use, with one or more threads, e.g. internal threads, of a heater of a liquefier assembly. The head may comprise one or more, such as a pair of, flats, e.g. for engaging a tool. The head may comprise a polygonal cross-section, such as a hexagonal cross-section. The body may comprise a necked portion, for example between the connecting feature and the head.

The liquefier nozzle may comprise a coating. The coating may be on at least part of the nozzle, for example at least the second end of the insert. The coating may cover at least part of the second end of the body. The coating may cover at least part of, e.g. most or all of, the substantially contiguous surface. Preferably, the coating covers the external surfaces of the nozzle, with the exception of a sealing face at the first end of the body. This has been found to impart wear and corrosion resistance to the entire body, without compromising the seal between the nozzle and the mating face against which it is to be sealed.

The coating may be harder, e.g. may have a higher hardness, than at least one or each of the first and second material. The coating may have a modified chemical composition to reduce adhesion of molten plastic thereto.. The coating may comprise a hard material. The o coating may comprise a vapour deposition coating, for example a physical or chemical vapour deposition coating. The coating may comprise a diamond-like carbon coating. Alternatively, the coating may comprise a high velocity oxygen fuel coating.

Another aspect of the invention provides a method of manufacturing a liquefier nozzle for is an additive manufacturing system, e.g. a liquefier nozzle as described above. The method may comprise inserting an insert into a nozzle body. The method may comprise making, e.g. using a subtractive manufacturing process such as machining, the nozzle body. The method may comprise making, e.g. using a subtractive manufacturing process such as machining, the insert. The nozzle, body and/or insert may comprise any one or more features described above.

Another aspect of the invention provides a method of manufacturing a liquefier nozzle for an additive manufacturing system, the method comprising: providing a body formed of a first, thermally conductive material and having: a connecting feature at or adjacent a first, upstream end of the body for connecting the nozzle to a heater of a liquefier assembly; a receptacle extending from a second, downstream end of the body; and a filament passageway extending from the first end of the body to the receptacle and having a smaller diameter than the receptacle; providing an insert formed of a second, wear resistant material and having: a filament passageway extending from an upstream end of the insert; an outlet at a downstream end of the insert, which has a smaller diameter than the filament passageway of the insert; and a tapered transition joining the filament passageway to the outlet; and press-fitting the insert into an interference engagement within the receptacle of the body from the second end of the body, such that the filament passageways of each of the body and the insert are aligned with one another.

The method may comprise applying a coating to at least part of the nozzle, for example at least the first and of the insert. The coating may be applied to at least part of the second end of the body. The coating may be applied to the head, e.g. most of or the entire head. Preferably, the method comprises applying a coating to the external surfaces, for example all external surfaces, of the nozzle, e.g. with the exception of a sealing face at the first end of the body.

The method may comprise applying the coating using a vapour deposition process, for example a physical or chemical vapour deposition process. The vapour deposition process may, but need not, involve the use of a plasma. Preferably, the method comprises applying the coating using a physical vapour deposition process and/or the coating may comprise a diamond-like carbon coating. Alternatively, the method may comprise applying the coating using a high velocity oxygen fuel coating process.

Another aspect of the invention provides a method of recycling a nozzle, e.g. a nozzle as described above. The method may comprise heating the body, for example to a temperature above 300°C, preferably above 500°C and more preferably above 700°C. The method may comprise removing the insert from the body, e.g. from the receptacle of the body, whilst it is in the heated state, e.g. at said temperature.

The coefficient of thermal expansion of the first material may be at least 20% more than that of the second material, e.g. for facilitating insertion of the insert into the body.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. For example, the kit may comprise any one or more features of the nozzle relevant thereto and/or the method may comprise any one or more features or steps relevant to one or more features of the nozzle or the kit.

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 nozzle, body or insert 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.

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 nozzle, body or insert 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 nozzle, body or insert described above or an embodiment thereof.

A further aspect of the invention provides a computer program element comprising computer readable program code means for causing a processor to execute a procedure io to implement one or more steps of the aforementioned method.

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

A yet further aspect of the invention provides a computer readable medium having a program stored thereon, where the program is arranged to make a computer execute a procedure to implement one or more steps of the aforementioned method.

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.

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. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a side view of a nozzle according to an embodiment of the invention; Figure 2 is a section view through line A-A in Figure 1; Figure 3 is a side view of the body of the nozzle of Figure 1; lc) Figure 4 is a section view through line B-B in Figure 3; Figure 5 is a side view of the insert of the nozzle of Figure 1; and Figure 6 is a section view through line C-C in Figure 5.

Referring now to Figures 1 and 2, there is shown a liquefier nozzle 1 for an additive manufacturing system. The nozzle 1 includes a body 2 formed of a first material and an insert 3 formed of a second material and received within the body 2.

The body 2, shown more clearly in Figures 3 and 4, includes a cylindrical, threaded engaging portion 20 and a head portion 21. The threaded engaging portion 20 describes a first, upstream end 22 and the head portion 21 describes a second, downstream end 23. The head portion 21 has a hexagonal cross-section in this example and is joined to the threaded engaging portion 20 by a necked region 24.

The body 2 also includes a filament passageway 25, which extends from the first end 21 toward the second end 23, and a receptacle 26 extending from the second end 23 toward the first end 21. The filament passageway 25 has a first diameter, which is slightly larger than a filament to be received therein. The receptacle 26 has a second diameter, larger than the first diameter and is sized to receive the insert 3 in an interference fit. The filament passageway 25 is joined to the receptacle 26 by a radial step 27.

The insert 3, shown more clearly in Figures 5 and 6, includes a cylindrical base 30 and a conical tip 31. The base 30 describes a first, upstream end 32 and includes a downstream face 33 from which the conical tip 31 projects. The conical tip 31 has describes a second, downstream end 34 corresponding to a truncated apex of the conical tip 31.

The insert 3 also includes a filament passageway 35, which extends from the first end 32 toward the second end 34 and an outlet 36, which extends from the second end 34 toward the first end 32. The filament passageway 35 of the insert 3 has a diameter similar to that of the filament passageway 25 of the body 2. The outlet 36 has a smaller diameter than that of the filament passageway 35 and is joined to the filament passageway 35 by a tapered transition 37.

In this example, the filament passageway 35 is within the base 30 and extends substantially the entire length thereof, while the transition 37 and outlet 36 are both within the conical tip 31. The angle of the transition 37 is similar to that of the outer surface of the conical tip 31, such that a substantially constant thickness is described therebetween.

In the assembled condition, shown in Figures 1 and 2, the downstream face 33 of the base 30 of the insert 3 is substantially contiguous with the surrounding surface of the head portion 21, describing the second end 23. Thus, the protruding conical tip 31 is described entirely by the insert, which is particularly advantageous for the reasons given below.

The first material is thermally conductive to conduct heat from the heater (not shown) to a filament (not shown) received within the nozzle. In this example, the first material is copper alloy. The applicants have determined that an appropriate material has a composition including mainly copper, with the inclusion of 0.5%-1.5% chromium and 0.05%-0.25% zirconium. However, the skilled person will appreciate that other material may be suitable, such as copper alloys, but these should be selected to provide a balance between thermal performance and cost.

The second material is wear resistant to resist wear caused by high temperatures and pressures, particularly when processing aggressive materials, such as composites. The second material is a steel composition which is wear resistant, but which is also relatively machinable. The applicants have determined that an appropriate material has a composition including 1.00%-1.60% chromium, 0.90%-1.20% carbon, 0.30%-0.75% manganese, 0.10%-0.35% silicon, up to 0.40% nickel, up to 0.15% molybdenum, up to 0.05% of sulphur, up to 0.05% phosphorus, up to 0.05% vanadium and is substantially free of Tungsten, with the exception of impurities.

The applicants have also determined that the use of a first material having a coefficient of thermal expansion that is at least 30% more than that of the second material can be advantageous for recycling the insert. This difference enables the insert 3 to be more easily removed from the interference engagement within the body 2. More specifically, the body 2 can be heated to an appropriate temperature, for example 800°C, which increases the diameter of the receptacle 26. By then, the force required to push the insert 3 out of the io receptacle is greatly reduced, which enables the insert 3 to be separated more readily from the body, which facilitates recycling.

The regions of the internal passageway that are exposed to the greatest pressures, and therefore the greatest abrasion, and therefore requiring greater wear resistance, are those which describe the tapered transition 37 and the outlet 36. As such, these regions are described by the insert, and therefore are formed of the second, wear resistant material.

The outer surfaces that are exposed to the greatest abrasion include the outer surface and truncated apex 34 of the conical tip 31. These outer surfaces are dragged across molten material, which can both cause wear and result in the accumulation of debris. As such, it is beneficial if these surfaces have characteristics that reduce adhesion of molten plastic thereto. As mentioned above, these surfaces are provided entirely by the insert, and therefore are formed of the second, wear resistant material.

An optional feature of the invention provides a hardened coating 4 on at least these outer surfaces, as illustrated schematically in Figure 1. As a further optional feature, the coating 4 may be applied to at least part of the head portion 21, for example to reduce the possibility of delaminafion. In fact, the applicants have found that applying the coating 4 across the entire nozzle 1, with the exception of the upstream end 22, improves the performance of the nozzle, without having a detrimental effect on its thermal conductivity. The reason for omitting the coating 4 on the upstream end 22 is that the copper alloy material is able to deform more readily into engagement with the mating face against which it is to be sealed.

The hardened coating preferably also has a modified chemical composition that reduces adhesion of molten plastic to the coated surfaces. The applicants have determined that diamond-like carbon coatings are particularly well suited, especially those having such a modified chemical composition.

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. 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

Claims

A liquefier nozzle for an additive manufacturing system, the nozzle comprising a body formed of a first, thermally conductive material and an insert formed of a second, wear resistant material, the body having a connecting feature at or adjacent a first, upstream end of the body for connecting the nozzle to a heater of a liquefier assembly, a receptacle having a substantially constant cross-section extending from a mouth at a second, downstream end of the body and a filament passageway extending from the first end of the body to the receptacle and having a smaller diameter than the receptacle, the insert having a filament passageway extending from an upstream end of the insert, an outlet at a downstream end of the insert, which has a smaller diameter than the filament passageway of the insert, and a tapered transition joining the filament passageway to the outlet, wherein the insert is press-fit into an interference engagement within the receptacle of the body.
A liquefier nozzle according to claim 1, wherein the interference engagement between the insert and the body is able to withstand a push-out force of at least 80 N when the temperature of the nozzle is 300°C.
A liquefier nozzle according to claim 2, wherein the interference engagement between the insert and the body is able to withstand a push-out force of at least 100 N when the temperature of the nozzle is 350°C.
A liquefier nozzle according to claim 2 or claim 3, wherein the first material comprises a copper alloy having a yield strength of at least 150 M Pa and a thermal conductivity of at least 150 W/m K. A liquefier nozzle according to claim 4, wherein the first material comprises a composition with at least 97% copper, up to 2.0% chromium and up to 0.30% zirconium.
A liquefier nozzle according to any one of claims 2 to 5, wherein the second material comprises steel having a composition with less than 3.0% chromium, less than 0.10% vanadium, less than 0.20% Molybdenum and is substantially free of tungsten, with the exception of impurities. 3. 4. 5. 6.
A liquefier nozzle according to any preceding claim, wherein the insert and the second end of the body describe a substantially contiguous surface.
A liquefier nozzle according to claim 7, wherein the substantially contiguous surface is substantially perpendicular to the filament passageway and the insert comprises a tapered outer surface between the substantially contiguous surface and the outlet.
A liquefier nozzle according to any preceding claim, wherein the transition of the insert is within a tapered tip having a tapered outer surface with an angle similar to that of the transition such that a substantially constant thickness is described therebetween.
A liquefier nozzle according to any preceding claim comprising a coating on at least the second end of the insert, wherein the coating is harder than each of the first and second material.
A liquefier nozzle according to claim 10, wherein the coating covers substantially the external surfaces of the nozzle with the exception of a sealing face at the first end of the body.
A liquefier nozzle according to claim 11, wherein the coating comprises a diamondlike carbon coating.
A liquefier nozzle according to any one of claims 10 to 12, wherein the coating comprises a modified chemical composition to reduce adhesion of molten plastic thereto.
A method of manufacturing a liquefier nozzle for an additive manufacturing system, the method comprising: providing a body formed of a first, thermally conductive material and having a connecting feature at or adjacent a first, upstream end of the body for connecting the nozzle to a heater of a liquefier assembly; a receptacle having a substantially constant cross-section extending from a mouth at a second, downstream end of the body; and io 9. 10. 12. 13. 14.a filament passageway extending from the first end of the body to the receptacle and having a smaller diameter than the receptacle; providing an insert formed of a second, wear resistant material and having: a filament passageway extending from an upstream end of the insert; an outlet at a downstream end of the insert, which has a smaller diameter than the filament passageway of the insert; and a tapered transition joining the filament passageway to the outlet; and press-fitting the insert from the second end of the body into an interference engagement within the receptacle of the body, such that the filament passageways to of each of the body and the insert are aligned with one another.
15. A method according to claim 12 comprising press-fitting the insert into an interference engagement that is able to withstand a push-out force of at least 80 N when the temperature of the nozzle is 300°C.
16. A method according to any one of claims 12 to 15 comprising applying a coating to at least the first and of the insert using a vapour deposition process, wherein the coating is harder than each of the first and second material.
17. A method according to claim 16 comprising applying a coating to the external surfaces of the nozzle with the exception of a sealing face at the first end of the body.
18. A method according to claim 16 or claim 17, wherein the coating comprises a diamond-like carbon coating.
19. A method according to any one of claims 16 to 18, wherein the coating comprises a modified chemical composition to reduce adhesion of molten plastic thereto.
20. A kit of parts for assembly into a nozzle according to any one of claims 1 to 13, the kit comprising a body formed of a first, thermally conductive material and an insert formed of a second, wear resistant material, the body having a connecting feature at or adjacent a first, upstream end of the body for connecting the nozzle to a heater of a liquefier assembly, a receptacle having a substantially constant cross-section extending from a mouth at a second, downstream end of the body and a filament passageway extending from the first end of the body to the receptacle and having a smaller diameter than the receptacle, the insert having a filament passageway extending from an upstream end of the insert, an outlet at a downstream end of the insert, which has a smaller diameter than the filament passageway of the insert, and a tapered transition joining the filament passageway to the outlet, wherein the insert is configured to be press-fit, in use, into an interference engagement within the receptacle of the body.