GB2615832A

GB2615832A - Assembly for an extruder

Info

Publication number: GB2615832A
Application number: GB2202433.5A
Authority: GB
Inventors: Theobold Sam; Everitt Andrew; Roberts Dylan; Sherlock Michael
Original assignee: E3D Online Ltd
Current assignee: E3D Online Ltd
Priority date: 2022-02-22
Filing date: 2022-02-22
Publication date: 2023-08-23
Also published as: GB202202433D0

Abstract

An additive manufacturing assembly 10 is disclosed, for an additive manufacturing extruder 1 comprising a filament passageway defined by a heat sink 5 (Figure 8), a heated nozzle tip 14, and a filament tube 16 separating the nozzle and the heat sink. The extruder may further comprise ventilation means such as a fan or an air knife/jet 24 mounted on the sides and a flow passageway 25 limiting heat convection between the heat sink and nozzle. A resilient spring 13 may also keep the sink and nozzle apart. The filament may be driven through the extruder by a pair of opposed drive wheels, motor, and gear assembly (Figure 14). The assembly may be incorporated in a housing 2 (Figure 2) and mounted using a mounting pin MP (Figure 1).

Description

ASSEMBLY FOR AN EXTRUDER

This invention relates generally to additive manufacturing systems for producing three-dimensional (3D) parts and particularly to assemblies for extruders used in such systems.

More specifically, although not exclusively, this invention relates to such an assembly and an extruder or additive manufacturing system including such an assembly and a method of feeding a filament of build material through a liquefier.

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 out of 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.

Known liquefiers include a heated nozzle that receives a filament of build material from the drive mechanism via a heat sink. A filament passageway of the heat sink is typically connected to a filament passageway of the nozzle by an intermediate tube, which separates the heat sink from the heated nozzle and is often referred to as a heat break.

The heat break is designed to minimise conduction between the heated nozzle and the heat break, thereby to ensure that the build material remains solid within the heat sink, whilst melting within the heated nozzle. This imposes certain design constraints that would be appreciated by the skilled person.

A first aspect of the invention provides an assembly, e.g. for an additive manufacturing system, the assembly comprising a filament passageway described at least in part by a heat sink and an flow passageway having an outlet positioned for directing a flow of fluid across a downstream end of the filament passageway described by the heat sink.

The applicant has observed that the provision of a flow passageway that is positioned for directing a flow of fluid, such as air, across a downstream end of the filament passageway can improve drastically the effectiveness of the heat break.

The assembly may comprise a flow inducing means, e.g. for inducing a flow of fluid into the flow passageway and/or across a downstream end of the filament passageway described by the heat sink.

Another aspect of the invention provides an assembly, e.g. for an additive manufacturing system, the assembly comprising a filament passageway described at least in part by a heat sink and a flow inducing means for directing a flow of fluid across a downstream end of the filament passageway described by the heat sink.

The assembly may comprise an extruder assembly or sub-assembly, that is to say an assembly or sub-assembly configured to be incorporated within an extruder for an additive manufacturing system. The assembly may comprise a nozzle or nozzle tip, which may be heated. The filament passageway may be described in part by a nozzle or nozzle tip, which may be heated. The assembly may comprise a heat break or tube or filament tube, which may be between the nozzle or nozzle tip and the heat sink. The filament passageway may be described in part by a heat break or tube, e.g. a filament tube, between the nozzle or nozzle tip and the heat sink.

The flow passageway or outlet may be for directing or may direct, in use, a flow of fluid toward a heat break, which may be between the heat sink and a heated nozzle or nozzle tip. The method of feeding a filament may comprise directing a flow of fluid toward a heat break, e.g. between the heat sink and a heated nozzle or nozzle tip.

The filament passageway may be described in part by each of the heat sink, the heated nozzle and the filament tube. The outlet may be adjacent the tube, e.g. for directing a flow of fluid toward the tube between the heat sink and the nozzle.

Another aspect of the invention provides an assembly, e.g. for an additive manufacturing system, the assembly comprising a flow inducing means and a filament passageway described in part by each of a heat sink, a heated nozzle and a filament tube between the heat sink and the heated nozzle, wherein the flow inducing means is configured to direct, in use, a flow of fluid across the filament tube as a filament of build material advances io through the filament passageway.

Another aspect of the invention provides a method of feeding a filament through an assembly, e.g. of an additive manufacturing system, the method comprising directing or inducing a flow of fluid across a filament tube between a heat sink and a heated nozzle as a filament of build material advances through a filament passageway described in part by each of the heat sink, filament tube and heated nozzle.

The outlet may be adjacent the tube. The outlet may be for directing a flow of fluid toward the tube, e.g. between the heat sink and the nozzle tip.

The fluid is preferably air, although it may be any other fluid, such as a gas or liquid. The flow of fluid across the downstream end of the filament passageway described by the heat sink may comprise a jet of air. The flow of fluid directed toward the heat break or tube may comprise a jet of air. The outlet may be constricted. The outlet may direct or may be for directing a jet of air. The constricted outlet may provide or may be for providing, in use, a jet of air or an air jet, hereinafter air jet.

The assembly may comprise a housing, which may describe at least part of the flow passageway. The air jet may be directed, in use, across or along a side or end or or face, e.g. a lower side or end or face, of the heat sink or housing. The air jet may be directed, in use, toward the or a heat break or tube, which may be between the heat sink or housing and a heated nozzle or nozzle tip. The air jet may comprise an air knife or a flat jet.

The outlet may comprise a slit, which may extend along or across a side or face, e.g. a lower side or face, of the heat sink or housing. The outlet may comprise a plurality of holes, which may be arranged in a line. The line of holes may extend along or across a side or face, e.g. a lower side or face, of the heat sink or housing. The flow passageway may comprise a tapering passageway. The flow area of the tapering passageway may reduce, for example toward the outlet. The tapering passageway may comprise an inlet. The flow area of the tapering passageway may reduce from the inlet to the outlet. The tapering passageway may divert a flow of fluid passing therethrough, e.g. from a first direction to a second direction. The tapering passageway may turn or include a turn. The tapering passageway and/or outlet may be described at least in part by the housing.

io The flow passageway or part thereof may be for directing or may direct, in use, a flow of fluid around the filament passageway or the heat sink or the part of the filament passageway described by the heat sink, e.g. before it is directed across the filament tube. The method may comprise directing the flow of air across the heat sink, e.g. before it is directed across the filament tube. The flow passageway may extend from a fan-mounting side of the heat sink or housing. The flow passageway may extend into the housing. The flow passageway may extend around the filament passageway. The flow passageway may extend around the filament passageway and into the housing. The flow passageway may extend from the fan-mounting side, around the filament passageway and into the housing.

The housing may include a wall separating the fan-mounting side, which may be an external or outer side, of the housing from an inner side of the housing. The wall may comprise an aperture. The aperture may be aligned with at least part of the heat sink. The heat sink may comprise one or more cooling fins, e.g. radial cooling fins. The aperture may be aligned with at least one of the cooling fins, preferably a plurality thereof. At least part of at least one of the cooling fins may extend through the aperture, e.g. to the fan-mounting side. The aperture may allow a fluid flow induced, in use, by the flow inducing means to flow from the fan-mounting side around the cooling fin(s), through the wall and into the housing. The aperture may comprise or provide or describe an inlet of the flow passageway.

The outlet may be one, e.g. a first, of two or more, e.g. a plurality of, outlets. The flow passageway may comprise an outlet, e.g. another or second outlet, adjacent an inlet, or upstream end, of the filament passageway. The outlet or further or second outlet may be described at least in part by the housing.

The assembly may comprise a drive wheel, e.g. for advancing a filament of build material. The drive wheel may be a first of a pair of drive wheels, which may be opposed drive wheels, e.g. for advancing a filament of build material into the filament passageway. A second drive wheel of the pair may be movable, e.g. relative to the first drive wheel. The second drive wheel may be movable from an operating position, e.g. for engaging a filament therebetween. The second drive wheel may be movable to a latched position, e.g. for allowing a filament to be inserted into the filament passageway. The second drive wheel may be movable between the operating and latched positions.

to The second drive wheel may be movably mounted, e.g. relative to the first drive wheel, by a lever. The lever may be pivotally mounted relative to the heat sink. The assembly or lever may comprise a latch. The lever may comprise an integral latch, which may be at or adjacent a free end of the lever or an opposite end of the lever to its pivotal connection. The latch may be integral or formed integrally with the lever. The latch may be operable to releasably retain the lever in the latched position. The latch may be operable to releasably connect, latch or retain the lever to the heat sink or housing, e.g. in the latched position.

The latch may extend or project from the lever. The latch may be operable by urging part of the latch toward the lever, e.g. to latch or unlatch the lever or latch. The latch may comprise a handle and/or a hook. The latch may be operable by urging the handle toward the lever. The latch may comprise a spine, which may be flexible and/or may project from the lever. The spine may be configured to flex, in use, when the latch is operated. The spine may project perpendicularly or orthogonally from the lever. The handle may be substantially parallel to the lever and/or substantially perpendicular to the spine. The hook may depend from the handle. The heat sink or housing may comprise a catch. The latch may be operable to selectively engage the catch to latch the lever. The latch may be operable to disengage the catch to unlatch the lever.

The lever may comprise a knuckle, which may be pivotally received within a receptacle of the housing. The lever may be biased toward the operating position, e.g. by a resilient biasing means or element such as a spring. The resilient biasing means may be mounted to the lever and/or to the housing.

The assembly may comprise an input coupling, e.g. for receiving a drive torque from a motor. The assembly may comprise a gear train, which may operatively connect the input coupling to the drive wheel. The gear train may comprise two or more stages, e.g. reduction stages.

Another aspect of the invention provides an assembly, e.g. for an additive manufacturing system, the assembly comprising an input coupling, e.g. for receiving a drive torque from a motor, a drive wheel, e.g. for advancing a filament of build material, and a gear train operatively connecting the input coupling to the drive wheel, wherein the gear train comprises two or more stages, e.g. reduction stages.

to The provision of a multi-stage gear train enables each stage to have a different configuration that is suited to the load characteristics it must endure. For example, each stage may comprise a different type of gearset and/or at least part of the gears may be formed of different materials to be used for each stage.

Another aspect of the invention provides a method of feeding a filament through an assembly, or a liquefier, e.g. of an additive manufacturing system. The method may, but need not, comprise applying a drive torque to a gear train. The method may, but need not, comprise applying a drive torque to two or more stages, e.g. reduction stages, of a gear train. The method may comprise driving a drive wheel, e.g. with the gear train. The drive wheel may engage a filament of build material. The drive wheel may advance the filament into the liquefier.

The two or more stages of the gear train may comprise first and second stages.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. For example, the assembly may comprise any one or more features of the method of feeding a filament and/or of the method of assembling an assembly relevant thereto and/or each of the methods may comprise any one or more features or steps relevant to one or more features of the assembly.

A drive torque may be applied to a planetary gearset, which may have an output. The first stage of the gear train may comprise the or a planetary gearset. The first stage or the planetary gearset may be connected to the input coupling. The first stage or planetary gearset may comprise a sun gear, which may be connected or coupled to or include or provide the input coupling. The first stage or planetary gearset may comprise one or more, e.g. a plurality of, planet gears, such as two, three or more planet gears. The first stage or planetary gearset may comprise a ring gear, e.g. within which the sun and/or planet gears may be received or engagingly received. The planetary gearset may be assembled by placing or inserting the sun gear and/or planet gear(s) into the ring gear. The first stage or planetary gearset may comprise a carrier. The or each planet gear may be connected or mounted, e.g. rotatably connected or mounted, to the carrier. The carrier may be connected to the or each planet gear by rotatably coupling them to the carrier. The carrier may be connected or coupled to or include or provide the output.

io The gear train, e.g. the second stage of the gear train, may comprise a simple or compound gearset. The second stage of the gear train may comprise a spur gearset. The gear train, e.g. the second stage of the gear train, may comprise a pinion and/or an output gear. The output gear may be larger than the pinion. The second stage or the pinion may be coupled to the output of the planetary gearset, e.g. coupled or fixed to the carrier. The pinion may be coaxial with the input coupling. The second stage or the output gear may be coupled, e.g. coaxially coupled, to the drive wheel for rotation therewith. The pinion may be operatively connected to the output gear. The pinion may engage, e.g. directly, the output gear. The pinion may mesh, e.g. directly or indirectly, with the output gear. The output gear may be driven by the pinion. The method may comprise driving, e.g. with the pinion, an output gear.

The second stage may comprise one or more further gears. The one or more further gears may be between, and/or mesh directly or indirectly with, the pinion and/or the output gear. The drive torque may be applied to or via the one or more further gears. The gear train may comprise one or more further stages, e.g. between the first and second stages. The drive torque may be applied to or via the one or more further stages of the gear train.

At least part of the first stage of the gear train, e.g. one or more or each gear thereof or at least the teeth of such gear(s), may comprise a first material. The first material may comprise a polymer, such as a polyamide or acetal or another appropriate engineering polymer. At least part, e.g. the teeth, of one or more of the sun gear, planet gear(s) and ring gear may comprise the first material or a different polymer to the first material. At least part of the carrier and/or further stages may comprise the first material or a different polymer to the first material.

At least part of the second stage, e.g. one or more or each gear thereof or at least the teeth of such gear(s), may comprise a second material. The second material may be different from the first material. The second material may be stronger and/or tougher and/or more wear resistant than the first material. The second material may comprise a metal, which may be sintered, e.g. a sintered powder metal. The metal may comprise an alloy, for example an iron alloy. The sintered metal be infiltrated with a lubricant. At least part, e.g. the teeth, of the pinion and/or the output gear may comprise the second material or a different metal to the first material. At least part, e.g. the teeth, of the further gear(s) of the second stage (if present) and/or further stages may comprise the second material or a to different metal to the first material.

The housing may comprise a motor-mounting side. The gear train may be received or housed within the housing. The housing may comprise a first sub-housing and a second sub-housing. The first and second sub-housings may be connected, e.g. removably connected together.

The first sub-housing may house or receive at least part of the first stage of the gear train. The first sub-housing may comprise the motor-mounting side, which may be opposite the side to which the second sub-housing is mounted. The second sub-housing may house or receive at least part of the second stage of the gear train. The second sub-housing may comprise the fan-mounting side, which may be opposite the side to which the first sub-housing is mounted. The second sub-housing may comprise at least part of the heat sink.

The housing may comprise a first part and a second part. The first sub-housing may comprise the first and second parts. The second part may be connected, e.g. removably connected to the first part. The housing may comprise a third part, which may be connected, e.g. removably connected to the first part and/or to the second part. The second sub-housing may comprise the third part. The first, second and third parts may be connected, e.g. removably connected together. The first stage of the gear train may be received or housed between the first and second parts. The second stage of the gear train may be received or housed between the second and third parts.

The first or second part of the housing may describe the or a ring gear. The first part may have a first side. The first part may have a motor-mounting side, which may correspond to its first side. The first part may have a second side, e.g. opposite its first or motor-mounting side. The first part may have a planetary gearset side, which may correspond to its second side. The second part may have a first side, which may face the second or planetary gearset side of the first part. The second part may have a planetary gearset side, which may correspond to its first side. The second part may have a second side, which may be opposite its first or planetary gearset side. The second part may have a filament feed side, which may correspond to its second side. The third part may have a first side, which may face the second or filament feed side of the second part. The third part may have a filament feed side, which may correspond to its first side. The third part may have a second side, which may be opposite its first or filament feed side. The third part may have a fan-mounting side, which may correspond to its second side.

The ring gear may be described by the first part, e.g. on its second or planetary gearset side. Alternatively, the ring gear may be described by the second part, e.g. on its first or planetary gearset side. The second part may comprise a recess, which may be on its first or planetary gearset side and/or which may be for receiving or may receive at least part of the carrier of the planetary gearset. The second part may comprise an aperture or hole, which may extend from its first or planetary gearset side to its second or filament feed side. The aperture or hole of the second part may receive at least part of the carrier of the first stage of the gear train, e.g. of the planetary gearset. The aperture or hole of the second part may receive at least part of the pinion of the second stage of the gear train. The carrier and/or the pinion may extend through the aperture or hole of the second part, e.g. toward the third part.

The housing, e.g. the second or third part of the housing, may comprise or describe the filament passageway. The housing, e.g. the second or third part of the housing, may comprise or describe the heat sink. The heat sink may be described by the second part, e.g. on its second or filament feed side. The heat sink may be described by the third part, e.g. on its first or internal side. The heat sink may comprise or include or describe the filament passageway. The heat sink and/or the third part may comprise a third material.

The third material may be more thermally conductive than the first material and/or than the second material. The third material may comprise aluminium or aluminium alloy. The third material may comprise zinc, a zinc alloy, magnesium or a magnesium alloy or any other suitable material.

The drive wheel or the pair of drive wheels may be between the inlet or upstream end of the filament passageway and the adjacent outlet, e.g. the further or second outlet, of the flow passageway.

The axis of rotation of the drive wheel, e.g. the first drive wheel, may be offset from that of the input coupling. This provides flexibility in the positioning of the drive wheels, and therefore the location of the filament inlet to the assembly. More specifically, the pinion is coaxial with the input coupling, at the centre of the gear train, with the output gear and drive wheel offset therefrom so that the teeth of the pinion and output gear mesh. This enables o the output gear and drive wheel to be positioned anywhere around the periphery of the pinion, thereby enabling the filament inlet to be positioned on any side of, or aligned with, the centre of the housing. This design flexibility allows the assembly to be adapted to various additive manufacturing machine layouts and configurations.

The first sub-housing may be held or secured to the second sub-housing, e.g. by a fastening means. At least two of the first, second and third parts of the housing may be held or secured together, e.g. by a fastening means. The first and second parts may be held or secured together by fastening means, e.g. a first fastening means. The third part may be held or secured to the first and/or second parts by fastening means, e.g. a second fastening means, which may preclude the first and second parts from being separated from one another.

The assembly may comprise a motor. The motor may be mounted to the motor-mounting side of the housing or of the first sub-housing or of the first part of the housing. The motor may be mounted to the first part, e.g. on the opposite side thereof to the second part. The second fastening means may hold or secure the motor to the third part of the housing and/or may captivate the first and second parts, e.g. between the motor and the third part.

The assembly may comprise a fan. The fan may be mounted to the fan-mounting side of the housing or of the second sub-housing or of the third part of the housing. The fan may be mounted to the third part, e.g. on the opposite side thereof to the second part. The fan may be held or secured to the second part, e.g. such that the third part of the housing is captivated therebetween. The fan may be held or secured to the second part by a third fastening means.

At least one or each fastening means may comprise a fastener. The or each fastener may comprise a threaded fastener, such as a bolt or screw, which may have an enlarged head. The or each fastener may comprise a clip, clamp or any other mechanism suitable for holding, securing or fastening the aforementioned elements together. The first fastening means may comprise a clip. The second and/or third fastening means may comprise a threaded fastener, such as a bolt or screw, which may have an enlarged head.

The assembly may comprise one or more flanges, e.g. one or more mounting flanges. The or each mounting flange may comprise a hole. The hole may be configured to receive a to fastener or pin, e.g. a mounting fastener or mounting pin. The or each flange may be formed of a material configured to receive a self-tapping fastener. The or each flange may be formed of a polymeric material. Alternatively, the or each or at least one flange may be formed of a ductile steel or other metallic alloy.

The assembly may comprise at least one mounting pin, which may be elongate. The or at least one mounting pin may extend through the housing. The housing may comprise a mounting hole, which may extend therethrough, for example from a first side to an opposite side. The mounting hole may be at least partially described by at least one of the flanges. The mounting hole may be partially described by each of a pair of flanges. The pair of flanges may be spaced from one another and/or may be aligned. The mounting hole may be described in part by a space between the pair of flanges, which may correspond to a void in the housing. The mounting pin may project from at least one side, for example opposite sides, of the housing. The mounting pin may be perpendicular to the drive wheel, e.g. the axis or axis of rotation of the drive wheel. The mounting pin may comprise a first mounting pin.

The assembly may comprise a second mounting pin, which may be elongate. The second mounting pin may extend through the housing. The second mounting pin may project from at least one side, for example opposite sides, of the housing. The second mounting pin may be perpendicular to the drive wheel, e.g. the axis or axis of rotation of the drive wheel. The second mounting pin may be parallel to the first mounting pin.

At least one or each mounting pin may comprise a threaded fastener. The threaded fastener may comprise a head at one end, e.g. a first end. The threaded fastener may comprise a thread at one end, e.g. another end or a second end that may be opposite the first end. The threaded fastener may have a smooth and/or featureless and/or threadless portion, which may be between the head and the thread.

The assembly may comprise a heater. The heater may be connected to the heat sink or housing, for example by a resilient element. The assembly may comprise a nozzle. The nozzle may extend through the heater. The nozzle may comprise the or a tube, e.g. the or a filament tube. The nozzle may be releasably connected to the heat sink or housing. The nozzle may comprise and an enlarged tip, e.g. the aforementioned nozzle tip, against which the heater may be biased, e.g. by the resilient element. The outlet may be positioned for o directing a flow of fluid toward the filament tube between the heat sink and the heater.

Another aspect of the invention provides an extruder comprising the assembly.

Yet another aspect of the invention provides an additive manufacturing system. The additive manufacturing system may comprise an assembly as described above.

Another aspect of the invention provides a computer program element comprising and/or describing and/or defining a three-dimensional design, e.g. of one or more or all of the components of the assembly 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 one or more or all of the components of the assembly 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 one or more or all of the components of the assembly 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 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.

A yet further aspect of the invention provides a control means or control system or controller comprising the aforementioned computer program element or computer readable medium.

For purposes of this disclosure, and notwithstanding the above, it is to be understood that any controller(s), control units and/or control modules described herein may each comprise a control unit or computational device having one or more electronic processors. The controller may comprise a single control unit or electronic controller or alternatively different functions of the control of the system or apparatus may be embodied in, or hosted in, different control units or controllers or control modules. As used herein, the terms "control unit" and "controller" will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) or control module(s) to implement the control techniques described herein (including the method(s) described herein). The set of instructions may be embedded in one or more electronic processors, or alternatively, may be provided as software to be executed by one or more electronic processor(s).

For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present invention is not intended to be limited to any particular arrangement. In any event, the set of instructions described herein may be embedded in a computer-readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

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 o 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 perspective view of an extruder according to an embodiment of the invention from above; Figure 2 is a perspective view of the extruder of Figure 1 from below; Figure 3 is an enlarged view of the hot end of the extruder of Figures 1 and 2; Figure 4 is a partial section view through the extruder of Figures 1 to 3; Figure 5 is a view similar to that of Figure 1, with the fan removed; Figure 6 is a view similar to that of Figure 5, with the liquefier sub-assembly separated from the drive sub-assembly; Figure 7 is a perspective view of an internal side of the liquefier sub-assembly of Figure 6; Figure 8 is an enlarged view of the internal side of the liquefier sub-assembly of Figure 7, with the first drive wheel sub-assembly removed.

Figure 9 is an exploded view of the liquefier sub-assembly of Figure 7, with the first drive wheel sub-assembly and the ancillary drive wheel assembly both omitted; to Figure 10 is a perspective view of the heat sink part of the housing, which forms part of the liquefier sub-assembly of Figure 7; Figure 11 is a perspective view of the drive sub-assembly of Figure 6 with the motor omitted; Figure 12 is a perspective view of the drive wheel sub-assembly shown in Figure 11, with the first and second housing parts separated to reveal the planetary gearset; Figure 13 is a perspective view similar to that shown in Figure 12, but from the opposite side and Figure 14 is a perspective view of the drive sub-assembly of Figure 6 with the motor omitted, but with the second drive wheel sub-assembly shown with the third housing part removed.

Referring now to Figures 1 to 4, there is shown an extruder 1 for an additive manufacturing system. The extruder 1 includes a hot end 10 mounted to a housing 2. The hot end 10 includes a nozzle 11 and a heater 12 mounted to the housing 2 by a coil spring 13. The nozzle 11 has a nozzle tip 14, a connection sleeve 15 and a filament tube 16 joining the nozzle tip 14 to the connection sleeve 15.

The nozzle tip 14 has a conical downstream end 14a projecting from an enlarged head 14b and an upstream barrel portion 14c. The connection sleeve 15 includes a downstream end with a flange 15a, a threaded portion 15b extending from the flange 15a and an upstream portion 15c having a smooth, featureless outer surface. The connection sleeve 15 is received within and threadedly engages the housing 2. The filament tube 16 is press fit into the upstream end of the nozzle tip 14 and the downstream end of the connection sleeve 15.

The heater 12 is in the form of a sleeve within which a plurality of windings are received, which are connected to a power lead 12a and are operable to heat an inner metallic ring 12b. The heater 12 also includes a temperature sensor connected to a sensor lead 12c, which is configured to measure the temperature of the metallic ring 12b. The coil spring 13 is retained on the heater 12 by a barbed spigot 12d. The barrel portion 14c of the nozzle tip 14 is received within the metallic ring 12b, and the downstream end of the metallic ring 12b abuts the enlarged head 14b. The coil spring 13 is compressed between the heater 12 and the housing 2, such that the metallic ring 12a of the heater 12 is biased toward and against the facing annular surface of the enlarged head 14b.

The housing 2 forms part of a feed assembly 17, which also includes a fan 18 and an motor 19 mounted to respective sides of the housing 2. A pair of mounting pins MP are also included for mounting the extruder 1 to an additive manufacturing system. The housing 2 includes a pair of mounting holes Mkt, MH2 which receive the mounting pins MP. A first mounting hole MI-11 of the pair extends through the housing 2, while a second extends across an upper side of the housing 2. The housing 2 includes first, second and third parts 21, 22, 23, which are secured together to house the components of the feed assembly 17. The fan 18 is mounted to a fan-mounting side FMS of the housing 2, or of the third part 23 of the housing 2, by a pair of fasteners Fi. The fasteners Fi extend through opposite corners of each of the fan 18, the third part 23 of the housing 2 and threadedly engage inserts 22d in the second part 22 of the housing 2.

The filament tube 16 extends between the housing 2 and the heated nozzle tip 14, and is surrounded by the coil spring 13. As a result, the filament tube 16 provides an exposed heat break between the housing 2 and the heated nozzle tip 14. The housing 2 includes an air knife 24 for directing a flat jet of air through the coil spring 13 and between the housing 2 and the heated nozzle tip 14, which impinges on the filament tube 16 and enhances the effectiveness of the heat break. More specifically, the air knife 24 has been designed to reduce the amount of convection into the housing 2, therefore keeping the housing 2 cooler to improve the temperature differential between the heated nozzle tip 14 and the housing 2.

The air knife 24 is shown in Figures 3 and 4, where it can be seen that a tapering passageway 25 is described between the second and third parts 22, 23 of the housing 2. More specifically, the third part 23 includes a rounded, projecting lip 26, which is positioned immediately above a projecting lip 27 of the second part 22, with the tapering passageway described between facing surfaces of the projecting lips 26, 27.

Removal of the fasteners H reveals the fan-mounting side FMS of the housing 2, as illustrated in Figure 5. Another fastener H is located in the lowermost remaining corner, io which extends through each of the first, second and third parts 21, 22, 23 of the housing 2 and threadedly engages the motor 19. Removal of the fastener F2 releases the third part 23 of the housing 2 from the first and second parts 21,22 of the housing 2.

As illustrated in Figure 6, the third part 23 of the housing 2, together with the components that are retained thereon and therein, form a liquefier sub-assembly 3. The first and second parts 21, 22 of the housing 2, together with the components that are retained thereon and therein, form a drive sub-assembly 4. Yet another fastener Fs is located in the uppermost remaining corner, which extends through the first and second parts 21, 22 of the housing 2 and threadedly engages the motor 19.

Figures 7 to 9 illustrate more clearly the liquefier sub-assembly 3, which includes the hot end 10, a heat sink 5 and an ancillary drive wheel assembly 6. The heat sink 5 is formed integrally with the third part 23 of the housing 2 and includes tubular portion 50 describing a filament feed passageway 51 having an inlet 52 and an outlet 53 (shown in Figure 10). A barbed spigot 53a surrounds the outlet 53 and retains the coil spring 13 on the housing 2.

The tubular portion 50 includes three radial cooling fins 54 projecting outwardly therefrom and extending about its entire periphery.

A plurality of cooling pins 55 project from the fan-mounting side FMS of the third part 23 of the housing 2, toward the fan 18 when mounted. A peripheral wall 56 also projects from the fan-mounting side FMS of the third part 23 of the housing 2 and surrounds the cooling pins 55, but is interrupted across an upper edge of the housing 2 creating a first outlet for air flowing from the fan 18 toward the housing 2 in use.

A wall 23a of the third part 23 of the housing 2 separates the fan-mounting side FMS from a filament feed side FF51. The tubular portion 50 projects from the wall 23a on the filament feed side FFS1 and includes a pair of drive wheel cutouts 57 formed on each side of the filament feed passageway 51, thereby exposing a filament (not shown) within the filament feed passageway 51 in use.

As shown more clearly in Figure 10, the wall 23a includes an aperture 23b aligned with the radial cooling fins 54 and through which they extend from the tubular portion 50 on the filament feed side FFS1 to the fan-mounting side FMS. This aperture 23b allows an air flow induced, in use, by the fan 18 to flow from the fan-mounting side FMS around the radial cooling fins 54, through the wall 23a and into the space between the liquefier sub-assembly 3 and the drive sub-assembly 4, specifically between the second and third parts 22, 23 of the housing 2.

This flow of air feeds the air knife 24. More specifically and as illustrated more clearly in Figure 4, the inlet to the tapering passageway 25 is described between the free end of the lip 26 projecting from the third part 23, within the space between the second and third parts 22, 23 of the housing 2. The outlet is described by the free end of the lip 27 projecting from the second part 22. The facing surfaces of the lips 26, 27 both taper in the same direction, thereby directing the air flow toward the heat break between the housing 2 and the heated nozzle tip 14. It will be appreciated by those skilled in the art that this will create a flat jet of air. The applicant has observed that this flat jet of air both cools the filament tube 16 and creates a barrier between the heat sink 5 and the heated nozzle tip 14, inhibiting heat from being transmitted from the heater 12 to the heat sink 5.

The third part 23 of the housing 2 also includes a peripheral wall 23c projecting from the wall 23a on the filament feed side FFSi, which is interrupted across the upper edge of the housing 2 to create another outlet, adjacent the inlet 52 of the filament feed passageway 51, for the flow of air from within the housing 2. This, second outlet allows air flowing from the fan 18 and into the housing 2 to exit the top of the housing 2. The third part 23 of the housing 2 includes a pair of holes 23d that receive the first pair of fasteners Fi and a further hole 23e that receives the second fastener H. The hole pair 23d extend from the fan-mounting side FMS, through both peripheral walls 56, 23c to the filament feed side FFSi, while the hole that receives the second fastener F2 only extends through the wall 23a and the peripheral wall 23c on the filament feed side FFSi.

The ancillary drive wheel assembly 6 includes a lever 60 having a cylindrical knuckle 61 at a first, lower end thereof, which is pivotally received within a complimentary, C-shaped receptacle 62 projecting from a lower wall on the of filament feed side FFS1 of the third part 23 of the housing 2. The lever 60 also includes an integral latch 63 projecting from an upper end portion 64 of the lever 60. The latch 63 includes a hook 63a, which releasably engages a catch 65 on a facing side wall of the third part 23 of the housing 2. The lever 60 also includes a release handle 63b that extends from a free-end of the hook 63a and substantially parallel to, but offset from, the upper end portion 64 of the lever 60. A user is io able to squeeze the release handle 63b and the upper end portion 64 of the lever 60 together to raise the hook 63a and release it from the catch 65.

The ancillary drive wheel assembly 6 includes a spring 66, which is captivated between an the lever 60 and the facing side of the third part 23 of the housing 2, immediately below the latch 53 and catch 65. The ancillary drive wheel assembly 6 also includes an ancillary drive wheel 67 and ancillary drive wheel gear 68 rotatably fixed to a shaft 69, which itself is rotatably mounted to the lever 60 below and on the opposite side to spring 66. These features of the ancillary drive wheel assembly 6 are labelled in Figure 14. Mien the hook 63a is released from the catch 65, the lever 60 is biased toward the filament feed passageway 51 by the spring 67.

Removal of the fastener F3 joining the first and second parts 21, 22 of the housing 2 to the motor 19 releases the motor 19 from a motor-mounting side MMS of the first part 21, while the first and second parts 21, 22 of the housing 2 are held together by a pair of clips 40.

The clips 40 project from upper and lower central portions of the first part 21 of the housing 2. The clips 40 engage respective recesses 41 in upper and lower central portions of the second part 22 of the housing 2, thereby to retain the first and second parts 21, 22 of the housing 2 together.

Figures 11 to 13 illustrate more clearly the drive sub-assembly 4 with the motor 19 removed, which includes a first gear train stage 7 captivated between the first and second parts 21, 22 of the housing 2. A second gear train stage 8 and a primary drive wheel assembly 9 coupled to the second gear train stage 8 are both captivated between the filament feed side FFS1 of the third part 23 of the housing 2 and a filament feed side FFS2 of the second part 22 of the housing 2. In this example, the primary drive wheel assembly 9 and most of the second gear train stage 8 are retained on the third part 23 of the housing 2, and therefore form part of the liquefier sub-assembly 3.

More specifically, the primary drive wheel assembly 9 includes a shaft 90 to which a primary drive wheel 91 and a primary drive wheel gear 92 are rotatably fixed. These components are illustrated more clearly in Figure 14. The shaft 90 is supported at one end by a first shaft receptacle 93 in the third part 23 of the housing 2, and forms an interference fit therewith such that the shaft 90 is retained thereon. The shaft 90 is also supported at its other end by a second shaft receptacle 94 in the second part 22 of the housing 2, with which it forms a to clearance fit when the third part 23 is mounted to the first and second parts 21, 22 of the housing 2.

The second gear train stage 8 includes a pinion 80, which meshes with a larger output gear 81 that is also rotatably fixed to the shaft 90 of the primary drive wheel assembly 9. In some examples, the larger output gear 81 is formed integrally with the primary drive wheel gear 92. When the third part 23 of the housing 2 is removed from the first and second parts 21, 22 thereof, the shaft 90 of the primary drive wheel assembly 9 tends to remain in the first shaft receptacle 93 because of the interference fit therebetween. The pinion 80 is rotationally fixed to a carrier 70 of the first gear train stage 7. The carrier 70 is substantially triangular in plan and includes a boss 71 on a first of its sides, to which the pinion 80 of the second gear train stage 8 is either mounted or with which the pinion 80 is formed integrally.

The second part 22 of the housing 2 has a central hole 82 through which the boss 71 of the carrier 70 extends from a planetary gearset side PGS1 of the second part 22 to its filament feed side FFS2. In some examples, the central hole 82 is larger and receives a flanged roller bearing (not shown). The second part 22 of the housing 2 also includes a circular recess 72 within which the triangular body of the carrier 70 is received.

The first gear train stage 7 includes three planet gears 73 rotationally mounted to a second side of the carrier 70, opposite the first side. Each planet gear 73 is mounted adjacent one of the corners of the triangular carrier 70, although other carrier shapes are envisaged. The planet gears 73 are received within and engage a circular ring gear recess 74 formed in the first part 21 of the housing 2 on a planetary gearset side PGS2 thereof. The first gear train stage 7 also includes a sun gear 75 which engages and is captively retained by the planet gears 73 within the circular ring gear recess 74. The sun gear 75 includes an input coupling 76 in the form of a circular recess with a flat edge, which provides a keyway for a shaft of the motor 19. Other designs of input coupling 76 are also envisaged. A hole 21a in the first part 21 of the housing 2 extends from its motor-mounting side MMS to its planetary gearset side PGS2 to expose the input coupling 76 of the sun gear 75.

The second part 22 of the housing 2 includes a flange 22a on each lateral side and projecting from on its filament feed side toward the third part 23 of the housing 2. Each flange 22a describes part of the first mounting hole MI-11 and the space between the flanges 22a is free from obstructions when the extruder 1 is assembled, thereby to enable one of io the mounting pins MP to be inserted through the housing 2. A pair of further flanges 22b also project from the top of the second part 22 of the housing 2, which are in similar lateral positions to the flanges 22a projecting from on its filament feed side. Each further flange 22b describes part of the second mounting hole MH2 and the space between the flanges 22a is free from obstructions when the extruder 1 is assembled, thereby to enable the other mounting pin MP to be inserted and extend through and between them.

The second part 22 of the housing 2 includes a pair of first through holes 22c at opposite corners for receiving a respective one of the first fasteners Fi. Inserts 22d are located on the planetary gearset side PGS1 of the second part 22 of the housing 2 and threadedly engage the first fasteners Fi. The second part 22 of the housing also includes a pair of second through holes 22e at the remaining opposed corners for receiving the second and third fasteners F2, F3. Similarly, the first part 21 includes a pair of blank clearance holes 21b at opposite corners, which are aligned with the first holes 22c of the second part 22 of the housing 2 to enable the ends of the first fasteners Fi to be received, if they are of such a length that this is necessary. The first part 21 also includes a pair of through holes 21c for receiving the second and third fasteners, F2, F3, which threadedly engage the motor 19.

The first gear stage 7 provides a substantial reduction in speed from the input coupling 76 to the carrier 70, and therefore to the pinion 80 of the second gear train stage 8. The second gear train stage 8 then provides a further reduction from the pinion 80 to the output gear 81. It will be appreciated by those skilled in the art that the torque passing through the first gear train stage 7 will be substantially less than the torque passing through the second gear train stage 8. The applicant has recognised that this enables the gears 73, 74, 75 of the first gear train stage 7 to be formed of a softer and/or less wear resistant material than the gears 80, 81 of the second gear train stage.

Thus, the gears 73, 74, 75 of the first gear train stage 7 are preferably formed at least in part of a polymeric material, for example a polyamide or acetal, while the gears 80, 81 of the second gear train stage 8 are preferably formed of a metallic material, for example a metal alloy such as an iron alloy. The applicant has determined that forming the gears 80, 81 of the second gear train stage 8 from a sintered metal is particularly advantageous. The sintered metal may be infiltrated with a lubricant.

As is more clear from Figure 14, when the latch 63 of the ancillary drive wheel assembly 6 to is released from the catch 65, the spring 66 urges the ancillary drive wheel gear 68 into engagement with the primary drive wheel gear 92. In this position, the primary drive wheel 91 and ancillary drive wheel 67 are spaced so as to engage a filament of build material (not shown) therebetween. Rotation of the drive shaft of the motor 19 causes the sun gear 75 to rotate, which transmits torque from the motor 19 at a first rotational speed via the first and second gear train stages 7, 8 and to the primary drive wheel assembly 9 at a second speed, much slower than the first speed.

The skilled person will appreciate that the torque provided to the primary drive wheel assembly 9 is also much greater than the input torque, by virtue of the large reduction ratio provided by the first and second stages 7, 8. Thus, more compact and cost effective motors may be used. This enables the use of a smaller and more cost-effective motor 19. The use of a small motor and of polymeric material for the first stage 7 of the gear train both reduce the weight of the extruder 1, which the skilled person will appreciate is a critical factor to the performance of the machine, since the extruder 1 must be moved across the build bed in use.

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. For example, the air knife 24 may be replaced with any suitable device for introducing an air flow across the heat break, for example one or more focused air jets that need not be flat.

It is also envisaged that the air flow across the heat sink 5 may be omitted, relying solely on air flow across the heat break and passive cooling of the heat sink 5. Additionally or alternatively, the heat sink 5 may be cooled hydraulically or by any other suitable means. It is also envisaged that the first and second gear train stages 7, 8 incorporate different layouts and/or types of gearsets. The first and/or second gear train stages 7, 8 may also be formed of other materials, or even the same material as one another.

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

CLAIMSAn assembly for an additive manufacturing system, the assembly comprising a filament passageway described at least in part by a heat sink and a flow passageway having an outlet positioned for directing a flow of fluid across a downstream end of the filament passageway described by the heat sink.
2. An assembly according to claim 1 comprising a nozzle and a filament tube between the nozzle and the heat sink, wherein the filament passageway is described in part to by each of the heat sink, the nozzle and the filament tube, the outlet being adjacent the filament tube for directing a flow of fluid toward the tube between the heat sink and the nozzle.
3. An assembly according to claim 2, wherein the outlet comprises a constricted outlet for providing, in use, an air jet directed toward the filament tube between the housing and the nozzle tip.
4. An assembly according to claim 2 or claim 3, wherein the flow passageway comprises an air knife configured to direct, in use, a flat jet of air toward the tube, between the heat sink and the heated nozzle, and across the downstream end of the filament passageway.
5. An assembly according to any preceding claim comprising a housing within which the heat sink is incorporated, wherein the housing describes at least part of the flow passageway.
An assembly according to claim 5, wherein part of the flow passageway directs, in use, a flow around the heat sink.
7. An assembly according to claim 5 or claim 6, wherein the flow passageway extends from a fan-mounting side of the housing around the filament passageway and into the housing.
8. An assembly according to any preceding claim, wherein the flow passageway comprises another outlet adjacent an inlet of the filament passageway.
An assembly according to any preceding claim comprising a heater connected to the heat sink by a resilient element and a nozzle extending through the heater and including the or a filament tube releasably connected to the heat sink and an enlarged tip against which the heater is biased by the resilient element, wherein the outlet is positioned for directing a flow of fluid toward the filament tube between the heat sink and the heater.
An assembly according to any preceding claim, comprising a pair of opposed drive wheels for advancing a filament of build material into the filament passageway.
An assembly according to claim 10, wherein a second drive wheel of the pair is movable relative to the first drive wheel from an operating position, for engaging a filament therebetween, to a latched position, for allowing a filament to be inserted into the filament passageway.
An assembly according to claim 11, wherein the second drive wheel is movably mounted relative to the first drive wheel by a lever pivotally mounted relative to the heat sink, the lever comprising an integral latch operable to releasably retain the lever in the latched position.
An assembly according to any preceding claim comprising an input coupling for receiving a drive torque from a motor, a drive wheel for advancing a filament of build material within the filament passageway and a gear train operatively connecting the input coupling to the drive wheel, wherein the gear train comprises a first reducing stage, which includes a planetary gearset connected to the input coupling, and a second reducing stage including a pinion, which is coupled to an output of the planetary gearset, and an output gear, which is operatively connected to the pinion and coupled to the drive wheel for rotation therewith.
14. An assembly according to claim 13, wherein at least part of the first stage of the gear train comprises a first material and at least part of the second stage of the gear train comprise a second material which is more wear resistant than the first material. 10. to 12. 13.
15.
16.
17.
18.
19.
20.
21.An assembly according to claim 14, wherein the first material comprises a polymer and the second material comprises a metallic material.An assembly according to claim 15, wherein the second material comprises a sintered powder metal infiltrated with lubricant.An assembly according to any preceding claim comprising an elongate mounting pin which extends through the housing, projects from opposite sides thereof and is perpendicular to the drive wheel.An assembly according to claim 17 comprising a second elongate mounting pin which extends through the housing, projects from opposite sides thereof and is parallel to the first elongate mounting pin.An assembly according to claim 17 or claim 18, wherein the or each elongate mounting pin comprises a threaded fastener.An extruder comprising an assembly according to any preceding claim.An additive manufacturing system comprising an assembly according to any one of claims 1 to 19.