Patent Description:
Extrusion-based additive manufacturing systems, e.g. Fusion Filament Fabrication (FFF) systems, are used to build a physical object from a digital representation in a layer-by-layer manner by extruding, through a nozzle, a melted feedstock material.

The feedstock normally takes the form of a continuous filament of thermoplastic material. Commonly, the filament is fed from a spool and advanced through a movable extrusion head containing a liquefier assembly. The liquefier assembly is configured to melt the filament such that it can be extruded through a nozzle and deposited on a print bed.

The liquefier assembly includes a liquefier section, which can be in the form of a tube, along which the filament is advanced, and a heater or heater cartridge external of the liquefier tube. The heater heats the liquefier section and, by virtue of thermal transfer, the filament. The temperature of the filament is raised above its melting point, causing it to liquify and allowing the material to be extruded from the nozzle. Extrusion pressure is applied by virtue of the continual advancement of the filament upstream of the nozzle.

Traditionally, both the filament and the channel or passage within or extending along the liquefier section are of substantially circular cross-section. It has been observed that because of the low thermal conductivity of thermoplastic material, heat from the heater is not efficiently and quickly transferred to the centre of a circular filament. This, in turn, can have a negative impact on both the rate and quality of extrusion.

<CIT> describes an extrusion nozzle with a circular inlet opening, a non-circular taper downstream of the inlet opening and an outlet opening downstream of the non-circular taper. <CIT> describes a hand-held extruder with a flattened dispensing nozzle.

It is a first non-exclusive object of the invention to provide a liquefier that overcomes, or at least mitigates the drawbacks of the prior art.

It is a further non-exclusive object of the invention to provide an improved liquefier, liquefier tube, liquefier assembly, extrusion head and method manufacturing a liquefier.

Accordingly, a first aspect of the invention provides a liquefier according to claim <NUM>.

Another aspect of the invention provides a liquefier assembly according to claim <NUM>.

Another aspect of the invention provides an additive manufacturing system according to claim <NUM>.

Another aspect of the invention provides a method of manufacturing a liquefier tube according to claim <NUM>.

The method may comprise providing a tubular body having a substantially constant wall thickness.

The method may comprise providing, e.g. forming, attaching or connecting, an extrusion tip at the other end of the tubular body, e.g. opposite the inlet portion, to form an outlet for dispensing material in a molten state. Providing an extrusion tip may comprise forming, attaching or connecting the extrusion tip to the other end of the tubular body, e.g. opposite the inlet portion. The extrusion tip may form or describe an outlet, e.g. for dispensing material in a molten state.

The method may comprise deforming or crushing the tubular body at a location spaced from one of its ends, such that the tubular body transitions from the substantially circular inlet portion to the non-circular portion downstream of the inlet.

The method may comprise deforming the tubular body by hydroforming. Deforming the tubular body by hydroforming may comprise placing the tubular body, or a portion thereof, in a forming tool or between a pair of dies. Deforming the tubular body by hydroforming may comprise injecting fluid under pressure into a passageway described by the tubular body so as to deform the tubular body, or a portion thereof, e.g. such that it conforms to a profile described by the forming tool or pair of dies.

Another method of manufacturing a liquefier or liquefier tube, e.g. for use in an extrusion-based additive manufacturing system, which is not claimed, comprises deforming a first sheet of material to form a first part of a liquefier or liquefier tube, deforming a second sheet of material to form a second part of a liquefier or liquefier tube, and attaching the first part to the second part to form a tubular body of the liquefier or liquefier tube.

The method may comprise deforming the first sheet and/or the second sheet into a channel section. The method may comprise deforming the first sheet and/or second sheet using a press, forming machine or metal stamping machine. The method may comprise deforming the first sheet and/or the second sheet by hydroforming. The method may comprise deforming the first sheet and/or the second sheet by stamping or forming.

The first sheet and/or the second sheet may be or comprise metal, for example stainless steel. The first sheet and/or the second sheet may be or comprise brass, copper, tungsten, titanium, molybdenum, beryllium copper or any other suitable metal or alloy.

The first sheet and/or the second sheet may comprise a polymeric material. The method may comprise heating the first and/or second sheet prior to deforming, e.g. above its glass transition temperature and/or so as to increase ductility and/or malleability.

The first part and/or second part of the liquefier or liquefier tube may each comprise one half of the liquefier, liquefier tube or tubular body of the liquefier tube.

The first part may be attached to the second part by welding or brazing.

According to another aspect of the invention there is provided a method of manufacturing a liquefier according to claim <NUM>.

The first block and/or the second block may comprise a metal, e.g. stainless steel. The first block and/or the second block may be formed of or comprise brass, copper, tungsten, titanium, molybdenum, beryllium copper or any other suitable metal or alloy.

The first block and second block may be connectable, e.g. removably connectable, to one another so as to describe the liquefier, liquefier tube or a passageway thereof.

The liquefier may comprise a tube, or a hollow or tubular body, which may have a substantially circular cross-section. The outlet may comprise an extrusion tip, e.g. for dispensing material in a molten state.

The liquefier or body may have a substantially constant wall thickness.

Advantageously, providing a tubular body having a substantially constant wall thickness allows for easier, and cheaper, manufacture of the liquefier tube.

The extrusion tip may be formed of or comprise a nozzle. The method may comprise providing, for example forming, attaching or connecting, a nozzle, e.g. at the other end of the body.

The extrusion tip or nozzle may be connected, e.g. removably, to the liquefier or body. The extrusion tip or nozzle may be brazed or welded to the liquefier or body.

The method may comprise forming, attaching or connecting the extrusion tip or nozzle, e.g. removably, to the liquefier, liquefier tube or body. The method may comprise brazing or welding the extrusion tip or nozzle to the liquefier, liquefier tube or body, e.g. the other end of the body.

The non-circular portion of the liquefier or body may comprise a deformed or crushed portion.

In examples, deforming or crushing the liquefier or body or providing the non-circular portion comprises deforming or crushing the liquefier or body in a first region, e.g. to provide a first segment or section, and deforming or crushing the liquefier or body in a second region, e.g. to provide a second segment or section.

The non-circular portion may comprise the first segment or section and/or second segment or section.

The liquefier or body may be deformed, e.g. by crushing, a first region to provide a first segment of the non-circular portion.

The liquefier or body may be deformed, e.g. by crushing, a second region, downstream of the first region, to provide a second segment of the non-circular portion downstream of the first segment. The first segment and/or second segment may be non-circular.

In examples, deforming or crushing the liquefier or body comprises compressing the liquefier or body. Deforming or crushing the liquefier or body may comprise compressing the liquefier or body in a first region, e.g. to provide a first segment or section, and compressing the liquefier or body in a second region, e.g. to provide a second segment or section.

In embodiments, the method may comprise compressing, deforming or crushing the liquefier or body to a first extent in a first region, and/or compressing, deforming or crushing the liquefier or body to a second extent, e.g. greater than the first extent, in a second region, e.g. so as to provide a tapered profile.

The second region or second segment or section may be downstream of the first region or first segment or section.

The non-circular portion of the liquefier or body may extend along a portion of the length, e.g. along a longitudinal axis or principal axis, of the liquefier, liquefier tube or body.

The non-circular portion of the liquefier or body may comprise a tapered cross-sectional profile. The flow area of the passageway of the non-circular portion of the liquefier or body may comprise a tapered profile.

The non-circular portion may taper along a portion of the length, e.g. along a longitudinal axis or principal axis, of the liquefier or body. The non-circular portion may have a major dimension and a minor dimension. The minor dimension may taper, e.g. along a portion of the length of the non-circular portion. The minor dimension may decrease, e.g. along a portion of the length of the non-circular portion.

Providing a taper, as per embodiments of the invention, is advantageous in that as the filament is advanced along the liquefier or liquefier tube, the molten portion (located adjacent the wall of the tubular body) is moved toward the centre of the flow path or passageway. Further, the distance the heat has to travel to reach the centre of the passageway or flow path is decreased.

The non-circular portion of the liquefier or body may comprise a plurality of segments or sections. Each of the plurality of segments or sections may comprise a deformed or crushed segment of the liquefier or body. Each of the plurality of segments or sections may be arranged, e.g. in series, along the length of, or principal axis of, the liquefier, liquefier tube or body. Each of the plurality of segments or sections may be arranged along a longitudinal axis of the liquefier, liquefier tube or body.

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

The flow area of the passageway of or in the plurality of segments may have a different cross-sectional shape, configuration or cross-sectional profile, e.g. from one another. The flow area of the passageway of or in one, e.g. a first, of the plurality of segments may have a different cross-sectional shape, configuration or cross-sectional profile from the passageway of or in another, e.g. a second, of the plurality of segments.

A minor dimension of a first of the segments may be greater than a minor dimension, e.g. a corresponding minor dimension, of a second of the segments. A major dimension of the a first of the segments may be less than a major dimension, e.g. a corresponding minor dimension, of the a second of the segments. The second segment may be downstream of the first segment.

The first segment may be deformed so as to have a minor dimension which is greater than a minor dimension of the deformed second segment.

The method may comprise compressing the liquefier or body to a first extent or magnitude in a first region to provide the first segment, The method may comprise compressing the liquefier or body to a second extent or magnitude in a second region to provide the second segment. The second extent or magnitude may be different from, e.g. greater or less than, the first extent or magnitude.

In some examples, the first segment and the second segment, e.g. their major and/or minor dimensions, are rotationally offset or skewed from one another. The first segment and the second segment may be skewed or twisted from, or relative to, one another.

The first segment and second segment may comprise a skew angle described therebetween. The first segment may comprise a portion of the liquefier or body deformed or crushed in a direction that is skewed or rotationally offset relative to a direction in which the second segment is deformed or crushed.

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

The liquefier or body may be deformed such that a minor and/or major dimension of the first segment and a corresponding minor and/or major dimension of the second segment are rotationally offset from one another.

Providing rotational offset, or skew, helps improve the thermal transmission characteristics of the liquefier, liquefier tube or body by creating a tortuous flow path for the molten material. Such a flow path promotes mixing of the melted or molten material as it is advanced along the liquefier, liquefier tube or body, allowing for more even thermal distribution through the material.

The method may comprise compressing, deforming or crushing the liquefier or body in the first region in a first direction and compressing, deforming or crushing the liquefier or body in the second region in a second direction, the second direction being skewed or rotationally offset relative to the first direction.

The cross-section, e.g. the cross-sectional shape, of first segment (or the passageway thereof or therein) and/or second segment (or the passageway thereof or therein) may comprise an axis of symmetry. An axis of symmetry of the first segment (or the passageway thereof or therein), e.g. the cross-sectional shape thereof, and a corresponding axis of symmetry of the second segment (or the passageway thereof or therein), e.g. the cross-sectional shape thereof, may be rotationally offset or skewed from one another.

In embodiments, the liquefier or body comprises a substantially circular portion intermediate two or more segments. The liquefier or body may comprise a substantially circular portion intermediate the first segment and the second segment.

The liquefier or body may be deformed so as to comprise a substantially circular portion intermediate the first segment and second segment.

The non-circular cross-section of the non-circular portion (or the passageway thereof or therein), or the liquefier or body may be deformed such that, one or more segments thereof, may be substantially stadium shaped, disco-rectangular or obround.

The non-circular cross-section of the non-circular portion, or one or more segments thereof, (or the passageway thereof or therein) may be oval, elliptical, regular polygonal, irregular polygonal, simple convex polygonal or simple concave polygonal.

The non-circular cross-section of the non-circular portion, or one or more segments thereof, (or the passageway thereof or therein) may be star-shaped.

The transition or change from the substantially circular portion to the non-circular portion, or one or more segments thereof, may comprise a continual transition, gradual transition and/or tapered transition.

The transition or change from the substantially circular portion to the non-circular portion, or one or more segments thereof, may comprise a staged, discretised and/or stepped transition.

The first segment (or the passageway thereof or therein) may have a different cross-sectional shape, configuration or cross-sectional profile from the second segment (or the passageway thereof or therein).

In examples, the non-circular portion may comprise a first non-circular portion and a second non-circular portion. The first non-circular portion and/or second non-circular portion may comprise a plurality of segments or sections. Each of the plurality of segments or sections may comprise a deformed or crushed segment of the liquefier or body.

Each of the plurality of segments or sections may be arranged, e.g. in series, along the length of, or principal axis of, the liquefier, liquefier tube or body and/or first and/or second non-circular portion. Each of the plurality of segments or sections may be arranged along a longitudinal axis of the liquefier, liquefier tube or body.

The first non-circular portion and/or second non-circular portion, e.g. their major and/or minor dimensions, may be rotationally offset, twisted or skewed from one another. The respective segments or sections of the first non-circular portion and/or second non-circular portion, e.g. their major and/or minor dimensions, may be rotationally offset or skewed from one another.

The first non-circular portion and second non-circular portion may comprise a skew angle described therebetween. The skew angle may comprise <NUM>°, <NUM>°, <NUM>°, <NUM>° or another angle.

The first non-circular portion or plurality of segments or sections thereof may comprise a portion of the body deformed or crushed in a direction that is skewed or rotationally offset relative to a direction in which the second non-circular portion or plurality of segments or sections thereof is deformed or crushed.

Corresponding minor and/or major dimensions of the first non-circular portion and second non-circular portion may be rotationally offset or skewed from one another. The liquefier or body may be deformed such that a minor and/or major dimension of the first non-circular portion and a corresponding minor and/or major dimension of the second non-circular portion are rotationally offset from one another.

The first non-circular portion and second non-circular portion may comprise a transition region or zone therebetween. The transition region or zone may extend along a portion of the length of the liquefier, liquefier tube or body.

The transition region or zone may comprise or accommodate the skew of the first non-circular portion and second non-circular portion, or one or more segments thereof, relative to one another.

The method may comprise deforming, crushing or compressing the liquefier or body in the first region to form a first segment (or the passageway thereof or therein) having a first cross-sectional shape. The method may comprise deforming, crushing or compressing the liquefier or body in the second region to form a second segment (or the passageway thereof or therein) having a second cross-sectional shape, e.g. different from the first cross-sectional shape.

Deforming, crushing or compressing the liquefier or body may comprise placing the liquefier or body in a press. Deforming, crushing or compressing the liquefier or body may comprise placing the liquefier or body in a forming machine, e.g. between a punch and die or between a pair of dies.

The liquefier or body may be deformed, crushed or compressed by rollers, e.g. a pair of opposed rollers, for example so as to form a continuous transition between the inlet portion and the non-circular portion. The press may comprise one or more, e.g. opposed rollers. Deforming, crushing or compressing the liquefier or body may comprise deforming, crushing or compressing the liquefier or body in segments, e.g. discrete segments.

The liquefier, body or inlet portion thereof may have an internal diameter, which may be between <NUM> and <NUM>, for example between <NUM> and <NUM>, e.g. between <NUM> and <NUM>. The liquefier or body may have a diameter of <NUM> or <NUM>.

The liquefier or body may comprise a thin-walled tube. The liquefier or body or thin-walled tube may comprise a, or be formed of, a thermally conductive material.

The liquefier or body may have a wall thickness of less than <NUM>, preferably less than <NUM>, for example between <NUM> and <NUM>.

The liquefier tube or body may have a length of <NUM> or less, for example <NUM> or less or <NUM> or less, e.g. <NUM> or less. The liquefier or body may have a length of between <NUM> and <NUM>, for example between <NUM> and <NUM>, e.g. between <NUM> and <NUM>.

The liquefier, liquefier tube or body may comprise a heating zone. The heating zone may be configured to be heated, in use. The heating zone and non-circular portion may coincide or overlap. The heating zone may encompass or span the non-circular portion.

The heating zone may be a portion or length of the liquefier or body at or to which heat is applied, e.g. so as to melt a filament material being advanced therealong. The heating zone may have a length of less than <NUM>, for example less than <NUM>, less than <NUM>, less than <NUM> or less than <NUM>. The heating zone may have a length of <NUM>, <NUM> or <NUM>.

The extrusion tip or nozzle may have an internal diameter which is smaller than that of the liquefier or body. The extrusion tip or nozzle may have a diameter of <NUM> or less, for example <NUM> or less. The extrusion tip or nozzle may have a diameter of between <NUM> and <NUM>, e.g. between <NUM> and <NUM> or between <NUM> and <NUM>.

The extrusion tip or nozzle (or the passageway thereof or therein) may comprise a substantially circular portion or substantially circular cross-section.

The non-circular portion, or one or more segments thereof, may be intermediate the inlet and outlet.

In embodiments, the substantially circular portions (or the passageway thereof or therein) and the non-circular portions, or segments thereof, may all have substantially equal cross-sectional areas. The non-circular portion, or one or more segments thereof, (or the passageway thereof or therein) may have a substantially constant cross-sectional area. The passageway of or in the non-circular portion, or one or more segments thereof, may have a substantially constant flow area.

The liquefier or body may be deformed such that the passageway of or in the substantially circular portion and the non-circular portion have substantially equal flow areas.

The liquefier or body and/or passageway may have or comprise a constant or substantially constant hydraulic diameter. The non-circular portion, first non-circular portion and/or second non-circular portion may have or comprise a constant or substantially constant hydraulic diameter.

The hydraulic diameter is defined by the following equation: <MAT>.

Where DH is the hydraulic diameter, A is the flow area and P is the perimeter described by the tubular body.

The provision of a liquefier or liquefier tube having a constant or substantially constant hydraulic diameter provides, in use, a substantially constant pressure as a filament material is being advanced therealong.

Therefore, in the case of a liquefier or liquefier tube, the change in cross-sectional shape in the non-circular portion, first non-circular portion and/or second non-circular portion allows for more effective heat transfer to a filament material as is being advanced, but whilst without increasing the required applied pressure to generate a given flow rate.

The liquefier or body may be made or formed of or comprise metal. The liquefier or body may be made of or comprise stainless steel. In embodiments, the liquefier or body may be made of or comprise brass, copper, tungsten, titanium, molybdenum, beryllium copper or any other suitable metal or alloy.

The liquefier or body may be made of or comprise a polymeric material, e.g. a thermally conductive polymeric material. Such polymeric material preferably has a melting point and/or glass transition temperature substantially higher than the filament material to melted.

According to another aspect of the invention, there is provided a liquefier assembly for use in an extrusion-based additive manufacturing system, the liquefier assembly comprising a liquefier or liquefier tube as described above, and a heating means, e.g. a heater, heating element, heater element or heater cartridge, for heating a filament of material advanced, in use, into and/or along the liquefier or liquefier tube.

The heating means may comprise a heating block or heater block. The heating block or heater block may comprise a heating element or heating cartridge. The heating means may at least partially surround the liquefier or liquefier tube and/or may surround or lie adjacent a heating zone of the liquefier or liquefier tube. The heating element or heating cartridge may extend along the length of the heating block or heater block.

The heating means, e.g. the heater, heating block or heater block, may clamp around the liquefier or liquefier tube. The heating means, heating block or heater block may comprise a temperature sensor. The heating cartridge or heating element and/or temperature sensor may each be operatively connected with a controller, e.g. so as to provide closed-loop temperature control.

According to a further aspect of the invention, there is provided an extrusion head or extruder comprising a liquefier or liquefier tube as described above, or a liquefier assembly as described above.

The extrusion head or extruder may comprise a feeder or feeding mechanism. The feeder or feeding mechanism may be located upstream of the liquefier, liquefier tube or liquefier assembly. The feeder or feeding mechanism may be configured to advance a filament of material, in use, into and/or along the liquefier or liquefier tube.

The feeder or feeding mechanism may comprise one or more rotatable members or gears, which may be configured to contact, in use, a surface of a filament being fed or advanced into the liquefier, liquefier tube or liquefier assembly.

The feeder or feeding mechanism may comprise a pair, e.g. of opposed, rotatable members or gears, which may be configured to contact, in use, a surface of a filament being fed or advanced into the liquefier, liquefier tube or liquefier assembly.

The feeder or feeding mechanism or one or more rotatable members may comprise a feed roller. The feeder or feeding mechanism or one or more rotatable members may comprise a pair of feed rollers.

At least one or each of the feed rollers may be driven, e.g. by a stepper motor.

One or more of the rotatable members may comprise one or more surface features, which may be configured to engage with or grip, in use, a surface of a filament of material received within or being fed or advanced into the liquefier, liquefier tube or liquefier assembly.

The surface feature(s) may comprise one or more topographical feature(s). The surface feature(s) may comprise one or more groove(s), protrusion(s) or rib(s).

According to another aspect of the invention, there is provided an additive manufacturing system comprising a liquefier or liquefier tube as described above, a liquefier assembly as described above or an extrusion head as described above.

The additive manufacturing system may be a fused filament fabrication (FFF) system.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. For example, the liquefier or liquefier tube may comprise any one or more features of the liquefier assembly, extrusion head or additive manufacturing system relevant to the liquefier or liquefier tube or vice-versa. Similarly, the method may comprise any one or more features or steps relevant to one or more features of the liquefier, liquefier tube, liquefier assembly, extrusion head or the additive manufacturing system.

Another aspect of the invention provides a computer program element comprising and/or describing and/or defining a three-dimensional design for use with a simulation means or a three-dimensional additive or subtractive manufacturing means or device, e.g. a three-dimensional printer or CNC machine, the three-dimensional design comprising an embodiment of the liquefier, liquefier tube, liquefier assembly, extrusion head and/or additive manufacturing system described above.

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.

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.

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

The extrusion head <NUM> includes a liquefier assembly having a liquefier tube <NUM> in this example (shown in <FIG>, in particular), a heating means H in the form of a heating element in this example, for heating a filament of material received within the liquefier tube <NUM>, and a feeding mechanism <NUM> for advancing a filament of material along the liquefier tube <NUM>.

Referring now to <FIG>, there is shown a liquefier tube <NUM> for use in the manufacturing system <NUM> of <FIG>.

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

A first, upstream end of the liquefier tube <NUM> is provided with an inlet portion <NUM> of substantially circular cross-section. A second, downstream end <NUM> of the liquefier tube <NUM>, opposite the inlet portion <NUM>, is also provided with a substantially circular cross-section. The inlet portion <NUM> and second end <NUM> are located at opposite ends of the tubular body <NUM>.

Intermediate the inlet portion <NUM> and second end <NUM> is a non-circular portion <NUM> having a non-circular cross-section, in the form of an obround cross-section in this example. In the present example, the non-circular portion <NUM> extends uninterrupted along a portion of the length of the tubular body <NUM>, and has a substantially constant cross-sectional area. A first end portion <NUM>, having a substantially circular cross-section extends along a portion of the length of the tubular body <NUM> between the inlet portion <NUM> and non-circular portion <NUM>.

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

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

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

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

Throughout the non-circular portion <NUM>, the minor dimension M2 is less than the diameter of the inlet portion <NUM> and second end <NUM>. Therefore, the distance from the sidewall of the tubular body <NUM> to the centre of the passageway P is reduced in the non-circular portion <NUM> when compared to the substantially circular cross-section of the inlet portion <NUM> and second end <NUM>.

Downstream of the fourth segment 53d the non-circular portion <NUM> transitions from a non-circular cross section to a second end portion <NUM> having a substantially circular cross section at the downstream end <NUM>. The second end portion <NUM> extends along a portion of the length of the tubular body <NUM> between the non-circular portion <NUM> and downstream end <NUM>.

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

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

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

As the filament material is advanced from the inlet portion <NUM> toward the non-circular portion <NUM>, it becomes molten as a result of the heating. The cross-sectional shape of the filament material then conforms to the cross-sectional shape of the non-circular portion <NUM>.

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

Extrusion pressure is created by the feeding of filament upstream. The molten filament is extruded from the extrusion tip <NUM> and onto the print bed <NUM> (as shown more clearly in <FIG>, in particular).

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

In this example, deforming or crushing the tubular body <NUM> is carried out by compressing the tubular body <NUM> at discrete points along its length using a press.

An extrusion tip <NUM> is connected to the tubular body <NUM> at the other end <NUM>, opposite the inlet portion <NUM>, to form an outlet for dispensing filament material in a molten state. The extrusion tip <NUM> is welded to the tubular body <NUM> in the present example.

Referring now to <FIG>, there is shown a liquefier tube <NUM> according to another example of the invention, for use in the manufacturing system <NUM> of <FIG>. The liquefier tube <NUM> according to this example is similar to liquefier tube <NUM> according to the first example, wherein like features will be denoted by like references incremented by '<NUM>'.

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

Intermediate the inlet portion <NUM> and second end <NUM> is a first non-circular portion <NUM> having a non-circular cross-section, in the form of an obround cross-section in this example. The first non-circular portion <NUM> is similar to non-circular portion <NUM> of liquefier tube <NUM>, and extends uninterrupted along a portion of the length of the tubular body <NUM>, and has a substantially constant cross-sectional area. A first end portion <NUM>, having a substantially circular cross-section extends along a portion of the length of the tubular body <NUM> between the inlet portion <NUM> and first non-circular portion <NUM>.

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

Downstream of the first non-circular portion <NUM>, between the first non-circular portion <NUM> and the second end <NUM> is a second non-circular portion <NUM>. The second non-circular portion <NUM> is similar to the first non-circular portion <NUM>, but rotationally offset by <NUM> degrees.

The second non-circular portion <NUM> is similar to non-circular portion <NUM> of liquefier tube <NUM>, and extends uninterrupted along a portion of the length of the tubular body <NUM>, and has a substantially constant cross-sectional area. A second end portion <NUM>, having a substantially circular cross-section extends along a portion of the length of the tubular body <NUM> between the second end <NUM> and second non-circular portion <NUM>.

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

Between the first non-circular portion <NUM> and second non-circular portion <NUM> is a transition point or zone T at which the orientation of the non-circular part of the liquefier tube <NUM> is rotated by <NUM> degrees.

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

The tubular body <NUM> includes a continual transition when viewed downstream from the substantially circular cross section of the inlet portion <NUM> to the non-circular cross section of the first segment 153a. The cross sectional area at the inlet portion <NUM> is substantially equal to the cross sectional area of the first segment 153a in this example.

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

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

Throughout the first non-circular portion <NUM> and second non-circular portion <NUM>, the minor dimension M2 is less than the diameter of the inlet portion <NUM> and second end <NUM>. Therefore, the minimum distance from the sidewall of the tubular body <NUM> to the centre of the passageway P is reduced in the first non-circular portion <NUM> and second non-circular portion <NUM> when compared to the substantially circular cross-section of the inlet portion <NUM> and second end <NUM>.

Downstream of the fourth segment 158d the second non-circular portion <NUM> transitions from a non-circular cross section to the second end portion <NUM> having a substantially circular cross section at the downstream end <NUM>. The second end portion <NUM> extends along a portion of the length of the tubular body <NUM> between the second non-circular portion <NUM> and downstream end <NUM>.

???As in the case of liquefier tube <NUM>, the length of the perimeter described by the tubular body <NUM> in the first non-circular portion <NUM> and second non-circular portion <NUM> is greater than that at the first end portion <NUM> and second end portion <NUM>. This provides a greater contact area between the tubular body <NUM> and filament (not shown), increasing the rate of heat transfer.

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

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

As the filament material is advanced from the inlet portion <NUM> toward the first non-circular portion <NUM>, it becomes molten as a result of the heating. The cross-sectional shape of the filament material then conforms to the cross-sectional shape of the first non-circular portion <NUM>.

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

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

Extrusion pressure is created by the feeding of filament upstream. The molten filament is extruded from the extrusion tip <NUM> and onto the print bed <NUM> (as shown in <FIG>, in particular).

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

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

In the present example, deforming or crushing the tubular body <NUM> is carried out by compressing the tubular body <NUM> at discrete points along its length using a press.

An extrusion tip <NUM> is connected to the tubular body <NUM> at the other end <NUM>, opposite the inlet portion <NUM>, to form an outlet for dispensing material in a molten state. The extrusion tip <NUM> is welded to the tubular body <NUM> in the present example.

Referring now to <FIG>, there is shown a liquefier tube <NUM> according to another example of the invention, for use in the manufacturing system <NUM> of <FIG>.

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

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

In the present example, the first non-circular portion <NUM>, transition point or zone T and second non-circular portion <NUM> form a first element A of the liquefier tube <NUM> and are described by the halves 7a, 7b. The inlet portion <NUM> and first end portion <NUM> form a second element B of the liquefier tube <NUM>, separate from the first element A. The second end <NUM>, second end portion <NUM> and extrusion tip <NUM> form a third element C, separate from the first element A and second element B.

The second element B is secured to a threaded aperture described in first end <NUM> of the split heater block <NUM> by virtue of a threaded connection (not shown). Similarly, the third element C is secured to a threaded aperture described in the second end <NUM> of the split heater block <NUM> by virtue of a threaded connection (not shown).

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

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

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

To assemble the liquefier tube <NUM> of <FIG>, each of the halves 7a, 7b are secured together using screws (not shown), in this example. The two halves 7a, 7b describe the first element A.

The second element B is screwed into the threaded aperture described in the first end <NUM> and the third element C is screwed into the threaded aperture described in the second end <NUM>.

As is the case with liquefier tubes <NUM> and <NUM>, liquefier tube <NUM> is configured to be received within an extrusion head <NUM> of an extrusion-based additive manufacturing system <NUM> (as shown in <FIG>, in particular). The substantially circular cross-section of the inlet portion <NUM> is configured to receive, in use, a filament of material having a circular cross section from a feeding mechanism <NUM>.

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

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

In the present example, the liquefier tube <NUM> of <FIG> is manufactured by providing either a pair of metallic blocks, or a single metallic block and splitting it in two, and machining the profile of the first element A into a planar face of each so as to provide halves 7a, 7b.

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

The liquefier tube <NUM> is similar to liquefier tube <NUM>, and like features will be denoted by like references incremented by '<NUM>'.

The liquefier tube <NUM> differs from the liquefier tube <NUM> in the cross-sectional profile in the non-circular portion <NUM>.

Intermediate the inlet portion <NUM> and second end <NUM> is the non-circular portion <NUM> having a non-circular cross-section.

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

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

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

The advancement of filament material, in use, is similar to that described above in relation to liquefier <NUM>, <NUM> and <NUM> and, for the sake of brevity, will not be described further.

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

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

The liquefier tube <NUM> is similar to liquefier tube <NUM>, <NUM>, <NUM> and <NUM> and like features will be denoted by like references incremented by '<NUM>'.

The liquefier tube <NUM> differs from the above-described liquefier tubes in that the flow path or passageway P described thereby has a constant hydraulic diameter DH. The hydraulic diameter is defined by the following equation: <MAT>.

Where DH is the hydraulic diameter, A is the flow area and P is the perimeter described by the tubular body <NUM>.

Hydraulic diameter DH allows pipework of non-circular cross-section to be approximated as circular for the purposes of pressure drop and fluid flow rate calculations. Having a liquefier tube <NUM> having a constant hydraulic diameter DH provides, in use, a substantially constant pressure as a filament material is being advanced.

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

Intermediate the inlet portion <NUM> and second end <NUM> is the non-circular portion <NUM> having a non-circular cross-section. The first end portion <NUM>, second end portion <NUM> and non-circular portion <NUM> have a constant hydraulic diameter DH.

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

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

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

Downstream of the fourth segment 453d the non-circular portion <NUM> transitions sharply from a non-circular cross section to the second end portion <NUM> having a substantially circular cross section at the downstream end <NUM>.

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

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

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

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

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

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

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

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

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

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

Claim 1:
A liquefier (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) for use in an extrusion-based additive manufacturing system (<NUM>), the liquefier describing a passageway (P) having an inlet portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) with a substantially circular cross-section for receipt of a filament of material and an outlet (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) downstream of the inlet portion, wherein the passageway transitions from the inlet portion to a non-circular portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) downstream of the inlet portion and the non-circular portion or a segment thereof splays or flares toward a substantially circular portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) at or toward the outlet, the non-circular portion having a non-circular cross-section.