WO2015028809A1

WO2015028809A1 - Improvements relating to fused deposition modelling

Info

Publication number: WO2015028809A1
Application number: PCT/GB2014/052618
Authority: WO
Inventors: Christopher PURSSELL; Simon Leigh; Duncan Billson
Original assignee: The University Of Warwick
Priority date: 2013-08-29
Filing date: 2014-08-29
Publication date: 2015-03-05
Also published as: GB201315353D0

Abstract

A fused deposition modelling apparatus for forming a build using at least two different materials. The apparatus comprises an extrusion head (8) arranged to receive a first material comprising a feedstock material for extrusion from the extrusion head (5), and to also receive an elongate object (6) comprising a second material different to the first material. The extrusion head comprises an outlet (18) for extrusion of first material and is arranged to deliver at least part of the elongate object (6) through said outlet (18).

Description

Improvements relating to fused deposition modelling Field

This disclosure relates to a fused deposition modelling apparatus for forming an object (hereinafter referred to as a 'build') using at least two different materials, and to an associated method.

Background

Fused deposition modelling (FDM) is an additive layer manufacture technology for fabricating physical, 3-dimensional (3D) objects from computer-aided-design (CAD) models.

FDM operates on the principle of heating and then extruding a feedstock material, typically as a series of stacked, patterned layers, thereby to form a build.

FDM is known for its ability to rapidly produce complex 3D structures, traditionally in rapid-prototyping applications in which pre-manufacture designs are tested for form, fit and function. Some examples of FDM systems are the BitsfromBytes BFB 3000 and the Stratasys uPrint.

Summary

This disclosure provides a fused deposition modelling apparatus for forming a build using at least two different materials, comprising an extrusion head arranged to receive a first material comprising a feedstock material for extrusion from the extrusion head, and to also receive an elongate object comprising a second material different to the first material. The extrusion head may be arranged to deliver at least part of the elongate object through the same outlet from which the first material is extruded.

In various embodiments, the extrusion head is a co-extrusion head arranged to co- extrude the first and second materials.

The elongate object is introduced into first material passing along the extrusion flow within the extrusion head, so that extruded first material has at least part of said elongate object disposed within it. In various embodiments, the elongate object is a flexible, continuous object such as a flexible wire or other continuous fibre. All or part of the elongate object may be incorporated into the build. In some embodiments, a cutting unit is provided to cut the elongate object as the build is being formed so that a plurality of cut parts of the elongate object are incorporated into the build.

According to various embodiments, the one or more elongate objects (e.g: one or more continuous fibres) are included within the build to provide additional functional properties, e.g: increased mechanical strength, or electrical functionality (such as a pick-up coil), or optical functionality. To this end, the elongate object may comprise an electrically conductive object (e.g: a copper wire) and/or a reinforcing object (e.g: a reinforcing fibre) and/or an optically functional object (e.g: a fibre optic or

electroluminescent wire). In various embodiments, the extrusion head has a heating region for heating first material as it passes through the heating region. Preferably, the elongate object is received into the extrusion flow between the heating region and the outlet of the extrusion head. The heating region may comprise a chamber for heating first material as it passes through the chamber. Preferably, the elongate object is received into the extrusion flow between the chamber and the outlet of the extrusion head.

The extrusion head may have a first inlet for the first material and a second inlet for the elongate object. The second inlet may be arranged to receive the elongate object at an angle to the direction of flow of first material.

This disclosure also provides a fused deposition modelling method to form a build using at least two different materials. The method comprises receiving a first material comprising feedstock material for extrusion from a print head of a fused deposition modelling apparatus, and receiving, at the print head, an elongate object comprising second material different to the first material. In various embodiments, the elongate object is received separately from the feedstock material. Forming the build using the two materials comprises concurrently outputting, from the print head, first material and second material. The first and second materials are preferably output at the same speed. Brief Description of the Drawings

So that the invention may be more easily understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure l is a schematic of an FDM apparatus according to an embodiment;

Figure 2 is a schematic of an extrusion head according to an embodiment;

Figure 3 is a cross sectional view of an end region of the extrusion head;

Figure 4 illustrates co-delivery of a continuous fibre with molten thermoplastic material;

Figure 5 is an external view of an exemplary extrusion head, showing an additional reinforcing plate.

Figure 6 shows an exemplary 3D printed component fabricated by the FDM apparatus; Figure 7 shows stages in the generation of a computer model for the exemplary component of Figure 6.

Detailed Description

Figure 1 is a schematic of an FDM apparatus 1 according to an embodiment. The FDM apparatus 1 includes a build support in the form of a bed 2, a movable print head 3, a Cartesian motion stage 4 to move the print head, and an electronic system controller (not shown) to control the FDM apparatus to form a build in a layer-by-layer fashion based on a CAD model. The print head 3 is configured to receive a thermoplastic feedstock 5 for extrusion from the print head, and to also receive an elongate object in the form of a continuous fibre 6, at least part of which is included in the build, as described below.

In use, the electronic control system coordinates and controls the motion of the print head 3, the motion stage 4 and the bed 2 in order to execute deposition of material with incremental motion of the head and bed away from each other after each layer of the build 7 is formed.

The print head 3 comprises an extrusion head 8, shown in Figure 2. The extrusion head 8 receives the thermoplastic feedstock 5. The thermoplastic is heated in the extrusion head 8 until it is molten, and then deposited as a continuous "string" through the nozzle 9 of the head 8.

Any suitable thermoplastic materials may be used, including for example: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polycaprolactone (PCL), polyvinyl acetate (PVA), or Nylon. In some cases, additives may be included in the thermoplastic material to provide additional functionality. One example is the use of a carbon black based composites to provide the deposited material with electrical conductivity, as described in "A Simple, Low Cost Conductive Composite Material for 3D Printing of Electronic Sensors", S.J. Leigh, R.J. Bradley, CP. Purssell, D.R. Billson and D.A.

Hutchins, PLos One 7(11).

As shown in Figure 2, the extrusion head 8 comprises a cold end assembly 10 and a hot end assembly 11. The cold end 10 includes a feedstock forcing mechanism 12, which may comprise a leadscrew, auger or pinch wheel arrangement configured to force the feedstock material 5 into the hot end 11, where it is heated and becomes molten. The junction between the hot and cold ends is maintained at a temperature below the glass transition temperature of the feedstock material 5, so as to prevent the material 5 deforming before it has entered the hot end.

The hot end 11 comprises a melt chamber 13 and the nozzle 9. The melt chamber 13 comprises a channel in the form of a bore formed in a block of metal (e.g: brass or aluminium). A heater 14 heats the block so as to maintain the block at a temperature greater than the glass transition temperature of the feedstock material. The feedstock material 5 passes through the bore of the melt chamber 13, where it is heated and becomes molten, so that the extrusion flow of molten feedstock passes out of the melt chamber 13 and into the inlet 15 of the nozzle 9. The bore of the melt chamber may be slightly tapered or otherwise reduce in diameter along its length so that the diameter of the melt chamber outlet matches the diameter of the nozzle inlet 15. The nozzle 9 includes a channel to allow extrusion flow to pass into the nozzle inlet 15, through the nozzle 9, and out of the nozzle outlet 18.

The nozzle 9 is adapted to receive an elongate object in the form of a continuous fibre, which is introduced into the extrusion flow. As shown in Figure 3, the nozzle adaptation 9 comprises a further inlet channel 19, angled at for example 45 degrees to the extrusion flow, to receive the continuous fibre 6. The extra channel 19 is arranged to allow the continuous fibre 6 to be introduced into the extrusion flow between the melt chamber 13 and the nozzle outlet 18. The molten feedstock 5 pulls the continuous fibre 6 along the extrusion channel and out of the outlet nozzle 9. In this way, the continuous fibre 6 is delivered together with the molten feedstock 5 through the same outlet 18, as illustrated in Figure 4.

Referring to Figure 4, it can be seen that when the co-extruded continuous fibre 6 exits the nozzle of the extrusion head 8, it is immediately forced around a bend. Therefore, while the fibre could be co-extruded into free air, when used to fabricate layers, the fibre is also effectively pulled out of the nozzle by the motion of the head 8.

Thus, according to embodiments of the invention, an extrusion head 8 is provided which is configured to co-extrude thermoplastic material 5 together with an elongate object in the form of a continuous fibre 6. The continuous fibre 6 is located inside the thermoplastic material 5 as it is extruded. Since the thermoplastic material 5 and continuous fibre 6 are co-extruded, the head 8 may be referred to as a co-extrusion head.

Referring to Figure 5, in some embodiments, an additional plate 20, which may for example comprise a 3 mm thick steel plate, may be included to provide rigidity and to prevent either lateral forces on the nozzle or the force of the thermoplastic being pushed through the nozzle from breaking off part of the nozzle 9. The plate may be attached to the hot end mount points of the extrusion head 8 as shown in Figure 5. In embodiments, the plate may also serve to aid the feeding in of the continuous fibre into the inlet channel 19.

Figure 6 shows a 3D-printed component 21 fabricated by the FDM apparatus 1. To form the component, a simple cylinder was first modelled on a computer using a CAD modelling package. The model was exported in an STL file format before being sliced into 200 μπι layers and set to print as a cylindrical tube using appropriate software. The component was printed as a single-walled tube structure. Figure 7 shows the imported CAD model 22, a representation of the sliced model 23 and a close up 24 of the sliced part showing the printed layers. A continuous fibre in the form of a 125 μπι diameter copper wire was then supplied to the inlet passage 18, and the FDM apparatus 1 was instructed to form a build based on the computer model. The resulting fabricated component, shown in Figure 6, was a cylindrical tube component 21 having dimensions of 40 mm diameter and 15 mm height with an embedded copper wire structure in the form of an electrically conducting coil consisting of seventy five complete turns. The thickness of the wall of the tube is determined by the nozzle diameter (1 mm in this example) and layer thickness (200 μπι in this example), as such the fabricated wall thickness was 1.66 mm in this example.

After fabrication, the electrical resistance of the coil was measured. The measured electrical resistance between the two ends was 12.6 ohms, therefore confirming that the wire is continuous and that no breaking of the wire had occurred during fabrication.

When fabricating components containing smaller radii, it has been found that sharp changes in the nozzle direction during formation of the build can cause the fibre to slice through the partially molten layer in which it had been deposited. Although the motion speed of the head could be reduced in order to give the molten plastic time to harden sufficiently to prevent the fibre slicing through the layer, this increases print time, especially for larger objects. In some embodiments, a cooling unit maybe provided to cool the freshly extruded material. This speeds up hardening of the thermoplastic so as to prevent the fibre slicing through the layer, even if sharp changes in the nozzle direction occur during formation of the build, without the need to reduce the motion speed of the head,

As will be understood from the foregoing, various embodiments of this disclosure provide a 3-D printer apparatus adapted to include at least one elongate object (e.g: a continuous fibre) within the build formed by the 3-D printer apparatus, to enhance the functionality of the finished object.

An FDM machine according to an embodiment of the invention may be realised by modifying a conventional FDM machine to include the nozzle adaptation 9 described above, so as to allow a continuous fibre 6 to be introduced between the melt chamber 13 and the nozzle outlet 18.

Alternatively, the continuous fibre 6 could be introduced immediately after the feedstock forcing mechanism 12, or immediately before the melt chamber 13. However, in these cases the difference in velocity of the thermoplastic feedstock 5 as it is forced into the smaller channel after the melt chamber may result in tension force being imparted in the fibre, which may prevent the continuous fibre from extruding at the same rate as the thermoplastic material at the nozzle outlet, or could even cause the fibre to break. Introducing the fibre between the melt chamber but before the nozzle outlet reduces such tension forces, thereby facilitating co-extrusion of the thermoplastic material and the continuous fibre.

It will be understood that FDM apparatus according to embodiments of the invention may comprise a print head having a plurality of extrusion heads, e.g: to receive feedstock of different materials or differently coloured materials, to allow multi- material 3D printing. One, some, or all of the extrusion heads may be adapted to receive respective continuous fibre(s) for incorporation into the build as described herein.

In some embodiments, extrusion heads may be adapted to receive one or more continuous fibres in order to impart multiple functionalities or superior functionality.

In some embodiments, a cutting device maybe provided to cut the received fibre during fabrication of the build. In this way many individual strands of any user-defined length maybe deposited throughout the build. Thus some embodiments provide an FDM apparatus which incorporates a plurality of elongate objects (e.g: a plurality of continuous fibres) within a build. The fibre, or fibres, may comprise electrically conductive fibre(s) (e.g: copper wire(s)), and may define one or more conductive paths in the eventual build. Alternatively, the elongate object(s) may comprise reinforcing fibres to increase mechanical strength. Alternatively, or in addition, other forms of fibre such as fibre optics for data communication could be used.

Those skilled in the art, cognizant of the present disclosure, will appreciate that in cases where multiple fibres are deposited, complex mechanical reinforcement structures could be produced, or short electrically conducting interconnects ("tracks") between other embedded devices and structures. It will be understood that a great many functional objects could be fabricated by incorporating one or more continuous fibre(s) in the build in accordance with embodiments of the invention. Many modifications and variations of the embodiments described above will be evident to those skilled in the art.

For example, although forming a build in a layer-by-layer fashion is described above, those skilled in the art will appreciate that a build need not be formed one layer at a time. For example, a robot arm could be provided to move the print head to a plurality of successive positions so as to form the build voxel-by-voxel, and the print head may move away from and return to a particular layer several times during formation of a build. Furthermore, although the FDM apparatus described above receives feedstock in the form of a filament of thermoplastic material, those skilled in the art will appreciate that feedstock material could alternatively be received in a chipped or pelletised form via a hopper system. It will also be understood that in some embodiments feedstock materials other than thermoplastics could be used, for example viscous liquids or clays.

Many further modifications and variations will be evident to those skilled in the art, that fall within the scope of the following claims:

Claims

1. A fused deposition modelling apparatus for forming a build using at least two different materials, comprising an extrusion head arranged to receive a first material comprising a feedstock material for extrusion from the extrusion head, and to also receive an elongate object comprising a second material different to the first material, wherein the extrusion head comprises an outlet for extrusion of first material and wherein the extrusion head is arranged to deliver at least part of said elongate object through said outlet.

2. A fused deposition modelling apparatus for forming a build using at least two different materials, comprising an extrusion head arranged to receive a first material comprising a feedstock material for extrusion from the extrusion head, and to also receive an elongate object comprising a second material different to the first material, wherein the extrusion head is configured to co-extrude said first and second materials.

3. A fused deposition modelling apparatus as claimed in any preceding claim, wherein the extrusion head comprises a heating region for heating the first material, and wherein the extrusion head is arranged to receive the elongate object into the extrusion flow between said heating region and said extrusion head outlet.

4. A fused deposition modelling apparatus as claimed in any preceding claim, wherein the extrusion head has a first inlet for said first material and a second inlet for said elongate object.

5. A fused deposition modelling apparatus as claimed in any preceding claim, wherein the extrusion head defines a path for the first material and wherein the extrusion head is configured to introduce the elongate object into first material passing along said path, so that extruded first material has at least part of said elongate object disposed within it.

6. A fused deposition modelling apparatus as claimed in claim 5, wherein the extrusion head is configured to receive the elongate object at an angle to said path.

7. A fused deposition modelling apparatus as claimed in any preceding claim, comprising a cooling device to cool the first material after it is extruded.

8. A fused deposition modelling apparatus as claimed in any preceding claim, wherein the elongate object comprises one of an electrically conductive fibre, a reinforcing fibre, and an optical fibre.

9. A fused deposition modelling apparatus as claimed in any preceding claim, further comprising a cutting unit to cut the elongate object as the build is being formed.

10. A fused deposition modelling apparatus as claimed in any preceding claim, further comprising:

a build support for supporting the build;

a motion stage configured to cause relative motion between the extrusion head and the build support; and

a controller configured to control the motion stage during formation of the build.

11. A fused deposition modelling apparatus, comprising a movement mechanism to move the extrusion head, and a controller configured to control the movement mechanism to move the extrusion head during formation of the build.

12. A fused deposition modelling method to form a build using at least two different materials, comprising:

receiving a first material comprising feedstock material for extrusion from a print head of a fused deposition modelling apparatus;

receiving an elongate object at the print head wherein said elongate object comprises second material different to the first material,

forming a build using the first and second materials, wherein forming the build includes concurrently outputting, from the print head, first material and second material.

13. A fused deposition modelling method as claimed in claim 12, wherein the first and second materials are output at the same speed.

14. A fused deposition modelling method as claimed in claim 12 or claim 13, wherein the first and second materials are output through the same outlet.

15 A fused deposition modelling method as claimed in any of claims 12 to 14 wherein the elongate object comprises one of an electrically conductive fibre, a reinforcing fibre and an optical fibre.

16. A fused deposition modelling method as claimed in claim 15, wherein the elongate object comprises a conductive wire.

17. A fused deposition apparatus substantially as herein described with reference to the accompanying drawings.