GB2597663A

GB2597663A - Mould for a composite Component

Info

Publication number: GB2597663A
Application number: GB2011435.1A
Authority: GB
Inventors: David Berg Christopher
Original assignee: ACORN2OAK INNOVATION SOLUTIONS Ltd
Current assignee: ACORN2OAK INNOVATION SOLUTIONS Ltd
Priority date: 2020-07-23
Filing date: 2020-07-23
Publication date: 2022-02-09
Also published as: GB202011435D0; WO2022018456A1

Abstract

A mould 1 for manufacturing a composite component comprises a first surface 5 defining at least part of a mould cavity 8 and at least one channel 20 for receiving heat transfer fluid; wherein heat transfer is provided between the channel and the mould surface to form the composite component. Preferably, the mould may comprise a plurality of channels, be made from X-ray transparent material, be made resiliently deformable and/or have a thickness that may be varied in different regions of the mould. A method of producing the mould uses additive manufacturing. A system for manufacturing components comprises the mould, a heat regulating device and a fluid delivery device. Preferably, the system comprises a compression device - which may comprise a deformable membrane, or an electromagnetic insert -for exerting a compressive force on the composite material. A method of manufacturing a composite component using the mould is further provided.

Description

Mould for a Composite Component The present invention relates to a mould for manufacturing a composite component, and in particular a mould comprising a channel, or channels, for receiving heat transfer fluid(s). The present invention further relates to a method of producing such a mould, a system for manufacturing a composite component using the mould, and a method of manufacturing a composite component using the mould.

Composite materials are materials comprising two or more chemically different constituents with differing physical properties. Depending upon the choice of the constituents, the composite material may exhibit enhanced physical characteristics that would not be possible using one of the constituents in isolation. A typical composite material comprises a polymer constituent, such as a thermoplastic material, and a fibre constituent, such as glass or Kevlar. The fibre constituent typically comprises a large number of individual fibres provided with a particular geometry, such as short or long strand fibres, or fibres that have been woven into a textile. Alternatively, the fibre constituent may be made from a recycled fibre material and therefore have a random geometry (e.g. random lengths or orientation). The polymer constituent typically comprises a mouldable material such as a thermoplastic or a thermoset material. The fibre constituent provides enhanced strength, whilst the polymer constituent binds the individual fibres together to prevent separation. Such fibre polymer composites can provide high strength of a level comparable to or higher than metals but exhibit a much lower density. As such, fibre polymer composites are often used in high-performance applications within the automotive and aerospace industries for reducing the weight of high-load components. Furthermore, because recycled fibres can be used composite constituents are also used to make products from recycled materials to reduce waste as part of the circular economy.

To manufacture a component from a composite material, it is known to provide a mould defining a negative image of the component to be manufactured. In some composite moulding processes, a composite material is laid upon, injected into, wrapped around or otherwise engaged with the mould so that the composite material conforms to the surface of the mould, thereby creating a positive image of the component. In some processes, the composite material may simply be left to cure at room temperature and atmospheric pressure. However, some materials, such as polymers, must be heated above a plastic deformation temperature before they are able to be deformed into the shape of the mould. In one known process, strands of carbon fibre are pre-impregnated within a thin covering of polymer and woven into a sheet of material before moulding, or a fibre fabric is injected with polymer material, and particulate additives, under pressure. In other processes, strands of fibre and strands of polymer may be co-mingled into a yarn, braided, woven or matted into a sheet of material. The pre-impregnated sheet of material is laid upon the mould so that the pre-impregnated sheet conforms to the contours of the mould. The mould and the pre-impregnated sheet are then placed into an oven. The oven heats the mould and the pre-impregnated sheet of material, causing the polymer coating surrounding each fibre to melt and thereby encapsulate the fibres in a single matrix conforming to the shape of the mould. Once moulded, the oven can be switched off and the mould left to cool in ambient air or forced cooled by circulating cold air over the mould and/or component.

In most industrial settings a single oven is used to make multiple different types of component. As such, the volume of the oven is often much larger than the volume of the component being made. Heating and cooling such a large volume of air can take a long time and can be costly in terms of energy consumption. Furthermore, to maintain profitability, it may be necessary to only run the oven when it is completely, or nearly, full. This can increase lead times for the manufacture of low-volume or specialist components. Additionally, if the component being manufactured is an odd shape or large size, it may not be possible to accommodate the component in the oven.

Moulds are typically made by machining a negative image of the component into a workpiece. The workpiece is often a cuboid block of material such as metal. The associated time taken and cost of manufacturing the mould therefore depend upon the size of the original workpiece and the amount of material that is machined from the workpiece. The high cost of machining means that often the mould has a similar overall spatial envelope to the original workpiece and comprises a relatively large volume of material. Because the mould is relatively large, it takes a relatively long time to heat in the oven and to cool it during the moulding process.

It is an object of the present invention to obviate or mitigate one or more problems associated with known moulds for manufacturing composite components, methods of producing such moulds, systems for manufacturing a composite component using such moulds, and methods of manufacturing a composite component using such moulds, whether identified herein or elsewhere. It is a further object of the invention to provide an alternative mould, method of manufacturing a mould, system for manufacturing a composite component and method for manufacturing a composite component.

According to a first aspect of the invention, there is provided a mould for manufacturing a composite component, the mould comprising: a first surface defining at least part of a mould cavity for receiving an unformed composite material; and at least one channel for receiving a heat transfer fluid; wherein the mould is configured to provide heat transfer communication between the channel and the first surface so as to form the composite material to the shape of the mould cavity.

It will be appreciated that to cause the unformed composite material to melt, the unformed material must be raised above a forming temperature. Conventional moulds do not comprise channels for receiving heat transfer fluid and must therefore be heated externally, for example placed in an oven, to raise the temperature of the mould itself and the temperature of the surrounding environment above the forming temperature of the unformed composite material. However, because the mould according to the first aspect of the invention includes a channel for receiving a heat transfer fluid, heat can be supplied to or extracted from the mould via the heat transfer fluid passing through the channel. Because the mould is in contact with the unformed composite material, the mould is able to conduct heat directly into the unformed composite material via the first surface, without the need for an oven to heat the mould and the surrounding environment. This reduces the overall thermal mass being heated compared to conventional moulding processes and therefore the overall amount of energy required to cause the composite material to reach the forming temperature is reduced. Furthermore, because a smaller thermal mass is required it is possible to achieve the forming temperature in a shorter period of time. Put another way, the temperature ramp up and cool down times may be reduced compared to using an oven. The above notwithstanding, it will be appreciated that it is possible to use the mould within an oven. In such cases, the channel provides the ability to more precisely control the heat within the mould itself and/or to heat the mould faster as compared to using the oven in isolation. In some embodiments, the oven air may be circulated through the channel, or the air may circulate through the channel naturally. The channel may reduce the thermal mass of the mould to provide faster heating and/or cooling. Furthermore, it will be appreciated that the use of a channel enables the path of the heat transfer fluid and the flow properties of the heat transfer fluid to be precisely controlled. Consequently, this provides a high degree of control over the heating and cooling of the mould.

The term "mould" encompasses a structure defining at least part of a negative image of a product to be manufactured. An alternative term for a "mould" is a "former'. The term "channel" encompasses an internal conduit defined by the mould for directing the flow of the heat transfer fluid. The term "heat transfer fluid" encompasses any fluid suitable for providing heat to or removing heat from the mould via the channel. The "first surface" may be a mould surface.

The mould may be additively manufactured. That is to say, the mould is manufactured using an additive manufacturing process. Because the mould is manufactured additively, in contrast to conventional subtractive manufacturing, this permits the creation of more complex geometries, and in particular enables the creation of one or more channels running through the body of the mould and closely following the contours of the first (i.e. mould) surface. This is particularly advantageous for moulds that are elongate as it may not be possible to machine the channels using subtractive manufacturing. Furthermore, additive manufacturing enables the creation of channels comprising twists, bends, elbows, internal turbulators, or the like which would otherwise be impossible to create in a single integral component using subtractive manufacturing.

The mould may comprise a plurality of channels. Where the mould comprises a plurality of channels, the available volume within the body of the mould for receiving heat transfer fluid is increased. Therefore a greater amount of heat can be transferred to and from the mould to provide improved heating and cooling. Put another way, increasing the number of channels provides improved thermal agility. This enables more precise temperature control and reduced heat-up and cool-down times. The channels may have the same or approximately the same cross-sectional areas available for fluid flow, alternatively the channels may have different cross-sectional areas or variable cross-sectional areas. Additionally or alternatively the mould may comprise a plurality of networks of channels. A "network of channels" encompasses one or more channels that are fluidly connected.

The plurality of channels define a concordant geometrical relationship relative to one another along at least a portion of their lengths. The term "concordant geometrical relationship" encompasses there being a geometrical relationship between the channels that is constant along the lengths of at least a portion of the channels or alternatively along the whole channel. By having a concordant geometrical relationship, it can be ensured that the fluid flow through the all of the channels has similar characteristics, such that the heating and cooling properties of the channels are consistent. This may ensure a more uniform transfer of heat into and out of the mould.

The concordant geometrical relationship may be selected from the group comprising (i) the channels extending in parallel to one another; (ii) the channels being offset from one another by an offset distance in a first direction and the channels extending along a second direction in which the offset distance is maintained; (iii) the channels extending helically wherein each channel defines the same helix angle; (iv) each channel defining a different radius of curvature about a common origin.

The mould may comprise a second surface on an opposite side of the mould to the mould cavity, and the second surface may define a generally conformal geometry in relation to the first surface. Put another way, the second surface may define an offset geometrical relationship in relation to the first surface, and the offset may be substantially constant for the whole or portions of the mould. As such, the mould closely "hugs" the shape of the component being manufactured, or, put another way, forms a shell-like structure conforming to the shape of the component. Because the second surface has a conformal shape in relation to the first surface, the size of the mould is reduced for example in comparison to prior art type moulds in which a mould surface may be machined into a large block of material. Reducing the size of the mould reduces the thermal mass of the mould and makes the mould faster to heat and cool using the heat transfer fluid.

The channel may be positioned closer to the first surface than the second surface.

When the channel is positioned closer to the first surface than the second surface, the channel is closer to the unformed composite material and therefore heat can be more efficiently transferred from the heat transfer fluid to the unformed composite material. Furthermore, because the channel is positioned closer to the first surface than the second surface the mould will be thicker on one side of the channel than the other. This thicker section of the mould is able to provide improved mechanical support for the mould.

The mould may define a longitudinal axis and a thickness in a generally radial direction with respect to the longitudinal axis; the mould cavity may define a width in a generally radial direction with respect to the longitudinal axis; and the thickness of the mould may be less than around 30 % of the width of the mould cavity. When the thickness of the mould is less than around 30 % of the thickness of the mould cavity, the thickness of the mould itself is relatively small in comparison to the width of the mould cavity. Put another way, the mould is relatively 'thin-walled' in relation to the mould cavity.

Therefore the volume of material defining the mould is reduced. Because less material is used to make the mould, the mould has a lower thermal mass and is faster to heat up and cool down. Put another way, the thermal agility (i.e. the ability of the mould to transfer heat efficiently) is increased.

The thickness of the mould may be less than around 25 cro of the width of the mould cavity, or may be preferably less than around 10%, 5 %, or 2.5 % of the width of the mould cavity. When the thickness of the mould is less than around 25 %, 10 %, 5 % or 2.5 % of the width of the mould cavity, the size of the mould is relatively small and has a low thermal mass to thereby provide faster heating and cooling.

The thickness of at least a portion the mould may be generally uniform. The term "generally uniform" encompasses some variation in the thickness of the mould, however this variation will generally be no more than around +/-10%, +/-5 % or +1- 1 % of the average thickness. The thickness of the mould may be generally uniform across at least a portion of the mould. The thickness of the entire mould may be substantially or generally uniform, or the thickness of only a portion of the mould may be substantially or generally uniform. In this context it will be appreciated that a portion of the mould is a localised region or part of the mould that does not constitute the entire mould.

The thickness of the mould may be varied in different regions of the mould in dependence upon the thickness of the unformed composite material. The unformed composite material may have sections that vary in thickness. Thinner regions of unformed composite material will reach the forming temperature faster, and therefore the thickness of the mould may be increased in the vicinity of the thinner regions to slow heating. Likewise, thicker regions of unformed composite material may require more time to reach the forming temperature, and therefore the thickness of the mould may be reduced in vicinity of the thicker regions to speed heating.

The mould may comprise one or more through holes connecting the channel and the first surface to provide fluid flow communication form the channels to the mould cavity. The lay-up material may be porous in its unformed state, and the through holes may permit heat transfer fluid to pass through the lay-up material to more efficiently raise the temperature of the lay-up material for forming.

The mould may be made from an X-ray transparent material. The term "X-ray transparent" encompasses materials that transmit at least 80 c/o, more preferably 90 % and most preferably 95 % of incident radiation having a wavelength in the range 0.01 to 10 nm. When an X-ray transparent material is used for the mould, the geometry of the composite material being moulded can be viewed using an X-ray spectroscopy machine. This enables the real time detection of defects within the composite material as it is being moulded, which can be used to adjust and improve the input parameters of the moulding operation (e.g. temperature ramp-up, pressure, mould geometry, or the like). The above notwithstanding, materials that transmit only 1 % of incident X-ray radiation may be suitable, however the definition of any defects visible by X-ray will be very low.

The mould may be resiliently deformable to permit adjustments to the geometry of the mould cavity. To this end, the mould may be made from a flexible (i.e. resiliently deformable) material. When the mould is resiliently deformable the geometry of the mould cavity can be adjusted to make minor alterations to the mould cavity. Adjusting the geometry of the mould cavity before and/or during the moulding process may permit the final geometry of the component to be correspondingly adjusted. Additionally or alternatively, adjusting the geometry of the mould cavity after the component has been moulded may permit the mould cavity to enlarge slightly such to aid the removal of the component from the mould cavity The mould may comprise an additively manufacturable material. For example: a polymer, a polymer-resin ceramic, or a metal powder. An addifively manufacturable material encompasses any material suitable for use in an additive manufacturing procedure to create the mould. This encompasses, for example: polymers, polymer-resin ceramics, metal powder, polymer hybrid materials, polymer-metal hybrids, wood-polymer hybrids, or the like. This may additionally include polymer materials with additives such as metal additives, graphene additives, nanoparticles or the like. Where graphene and/or metal are added to the additively manufacturable material, this may improve the transfer of heat in particular portions of the mould. For example, graphene and/or metal can be added near the first surface to improve heat transfer from the channel to the first surface.

The mould may comprise a port for supplying and/or removing heat transfer fluid to and from the channel and an outlet port for removing heat transfer fluid from the channel.

The first surface may be coated with a protective layer. When the first surface is coated with a protective layer or layers, this protects the mould from damage and enables the mould to be used in high volume production runs (i.e. used a relatively large number of times).

According to a second aspect of the invention, there is provided a mould assembly comprising a plurality of moulds according to the first aspect of the invention. Where more than one mould is used, it is possible to manufacture components that are large or complex in shape. This permits products that would previously have been assembled from multiple separate components to be manufactured monolithically using low density high strength materials. For example, the moulds may define separate sub-sections of the exterior of a component to be formed. The moulds may be assembled with one another in a modular fashion. The channel of one mould may fluidly communicate with one or more channels of an adjacent mould.

According to a third aspect of the invention, there is provided a method of producing the mould of the first aspect of the invention, the method comprising: obtaining an electronic file representing a geometry of the mould; and controlling an additive manufacturing apparatus to manufacture the mould according to the geometry specified in the electronic file. As previously noted, by manufacturing the mould using an additive manufacturing process, it is possible to create mould geometries that would otherwise not be possible or would be prohibitively expensive to produce using conventional subtractive manufacturing. This enables the creation of moulds with reduced thermal mass and integrally formed channels for carrying heat transfer fluid.

According to a fourth aspect of the invention there is provided a system for manufacturing a composite component, the system comprising: a mould according to the first aspect of the invention or a mould assembly according to the second aspect of the invention; a heat regulating device for controlling the temperature of the heat transfer fluid; and a fluid delivery device for supplying heat transfer fluid to the channel.

The heat regulating device permits the temperature of the heat transfer fluid to be controlled. Once the heat transfer fluid is at a desired temperature the delivery device enables the delivery of the heat transfer fluid to the channel. Additionally, the delivery device may comprise means for controlling the flow rate and/or the pressure of the heat transfer fluid delivered to the channel (for example a pump, throttle valve or the like).

Therefore, the amount of thermal energy delivered to or extracted from the mould via the heat transfer fluid is controllable by the system. In one example, the heat regulating device and the delivery device can be controlled to deliver a sufficient amount of energy to the unformed composite material via the mould such that the composite material reaches a temperature above a plastic deformation temperature. Once the composite material is above the plastic deformation temperature, the composite material will deform and adopt the shape of the mould cavity. For most polymer materials the temperature of the heat transfer fluid to raise the lay-up material above the plastic deformation temperature can be expected to be in the range of around 50 °C to around 450 °C and more, preferably within the range of around 100 °C to around 400 °C, or 150 °C to around 350 °C, or 200 °C to around 300 °C, or around 250 °C. In some embodiments, the temperature of the heat transfer fluid may be +/-10 °C, 20°C, 30°C, or 50 °C relative to the melting temperature of the lay-up material. Further still, the temperature of the heat transfer fluid may be +/-1 %, 2 °/0, 5 %, 10 % or 25 % of the melting temperature of the lay-up material. The heat regulating device may then be used to control the extraction of heat from the mould by providing heat transfer fluid at a lower temperature. In some embodiments, the fluid delivery device may additionally or alternatively supply heat transfer to a compression device (e.g. a bladder or an insert). The heat transfer fluid may be recirculated from the compression device to the channel or vice versa. A compression device may be provided to exert a compressive force upon the unformed composite material to form the composite material to the shape of the mould cavity. The mould and/or the compression device may be heated by the heat transfer fluid. The heat transfer fluid may heat the first surface to a temperature at least equal to or greater than a melting temperature of the unformed composite material.

The system may further comprise a compression device for exerting a compressive force upon the unformed composite material to form the composite material to the shape of the mould cavity. The compression device may enable the unformed composite material to be pressed against the first surface of the mould so that the surface area of the unformed composite material in contact with the mould increases, allowing for better transfer of heat to the composite material and enabling the composite material to take on the shape of the mould cavity during the forming process.

The compression device may be configured to receive a heat transfer fluid for controlling the temperature of the compression device. When the compression device receives a heat transfer fluid, the heat transfer fluid can transfer heat into or out of the compression device to control the temperature of the compression device. Controlling the temperature of the compression device enables more precise control of the temperature gradient over the composite material from the surface of the mould to the surface of the compression device. The compression device may receive the same heat transfer fluid as the channel of the mould. For example, the heat transfer fluid may be first passed through the channel and then passed through the compression device in series, or vice versa. Alternatively, the compression device may receive a separate heat transfer fluid, for example a heat transfer fluid from another source. Further still, the compression device and the channel of the mould may be fluidly connected in series, and a separate heat transfer fluid may be introduced between the compression device and the mould to adjust the temperature of one relative to the other.

The compression device may comprise: a deformable membrane; and a fluid pump, wherein the fluid pump is configured to control the pressure on one or both sides of the membrane to cause the membrane to exert the compressive force on the unformed composite material. The deformable membrane may be substantially any suitable membrane, for example a sheet of elastomeric material which may optionally be covered by a braided lining. During use, the membrane may be sealed against the mould using a gasket. The air within the mould cavity between the first surface and the membrane may be pumped out via a fluid pump so that the membrane conforms to the contours of the first surface to cause the unformed composite material to be compressed against the first surface. The deformable membrane may receive a heat transfer fluid on at least one side of the membrane.

The membrane may be an inflatable bladder or a vacuum bag. The inflatable bladder may receive a heat transfer fluid. The deformable bladder may comprise a pressure release valve or a throttle or the like to control flow out of the bladder.

The compression device may comprise an insert configured to be received within the mould cavity. The insert effectively 'sandwiches' the composite material against the mould, such that the composite material takes on the shape of the mould cavity. The insert may have a generally conformal geometry in relation to the mould cavity to enable compression of the composite material against the entire surface of the mould cavity. The insert may comprise one or more channels for receiving a heat transfer fluid.

The system may further comprise an electromagnet; the insert may comprise a magnetic component; and activation of the electromagnet may cause the insert to exert the compressive force on the unformed composite material. The insert may be magnetically repelled or attracted to the electromagnet to cause the application of the compressive force. The use of an electromagnet for applying the compressive force allows the compressive force to be supplied and removed instantaneously or in a controlled manner. The insert may comprise particles of magnetic material that have been mixed into the body of the insert, or the insert may comprise one or more portions of magnetic material (e.g. formed from a plate or the like) that are contained within the insert.

According to a fifth aspect of the invention, there is provided a method of manufacturing a composite component, the method comprising: providing a mould according to the first aspect of the invention or a mould assembly according to the second aspect of the invention; engaging an unformed composite material with the first surface; and supplying a heat transfer fluid to the channel to heat the unformed composite material via the first surface so as to form the composite material to the shape of the mould cavity. The unformed composite material may be engaged with the first surface in any suitable way. For example, the unformed composite material may be laid upon the first surface as a solid object, or may be introduced to the first surface in any other manner.

The method may further comprise manufacturing the mould using an additive manufacture process. The method may further comprise providing a compression device and exerting a compressive force upon the unformed composite material via the compression device to form the unformed composite material to the shape of the mould cavity.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: Figure 1 is a cross-sectional schematic side view of a first embodiment of a mould assembly; Figure 2 is a schematic plan view of a mould of the first embodiment; Figure 3 is a cross-sectional schematic side view of the first embodiment including a lay-up material and a compression device in pre-forming configuration; Figure 4 is a cross-sectional schematic side view of the first embodiment including a lay-up material and a compression device in a forming configuration; Figure 5 is a cross-sectional schematic side view of a second embodiment of a mould assembly; and Figure 6 is a schematic diagram of a system comprising a mould assembly.

Exemplary Embodiment Figure 1 shows a cross-sectional view of an example embodiment of a mould assembly 1 for manufacturing a composite component. The mould assembly 1 comprises a first mould 2 and second mould 3 that are assembled together in a shell-like fashion (alternatively, in the manner of an "Easter egg") to define a hollow region therebetween. The mould assembly 1 has a hollow tubular shape extending along a central axis 4. The first mould 2 comprises a first mould surface 5 and the second mould 3 comprises a second mould surface 6. The first and second mould surfaces 5, 6 collectively define a mould cavity 8 having substantially the shape of the composite component to be manufactured. In the illustrated embodiment, the component to be manufactured is cylindrical and therefore the mould surfaces 5, 6 are correspondingly cylindrical. The first mould 2 comprises a first outer surface 7 and the second mould 3 comprises a second outer surface 11. The first and second mould surfaces 5, 6 face radially inwardly with respect to the central axis 4, whilst the first and second outer surfaces 7, 11 face radially outwardly with respect to the central axis 4.

The first mould 2 comprises a first cylindrical wall section 9 extending along the central axis 4 that defines the first mould surface 5 and the first outer surface 7. The second mould 3 comprises a second cylindrical wall section 10 extending along the central axis 4 that defines the second mould surface 6 and the second outer surface 11. The thicknesses of the first and second cylindrical wall sections 9, 10 are substantially constant along the central axis 4, such that the first and second outer surfaces 7, 11 exhibit a generally conformal shape in relation to the first and second mould surfaces 5, 6. As such, the moulds 2, 3 effectively "hug" the contours of the component. Preferably, the thickness of the wall sections 9, 10 in the radial direction relative to the central axis 4 is no more than around 30 % of the overall diameter of the mould cavity 8. In general, it is preferable for the thickness of the moulds 2, 3 to be as thin as practical, and therefore the thickness of the wall sections 9, 10 to be no more than around 25 %, 10 °/0, 5 c/o or 2.5 % of the overall diameter of the mould cavity 8. For non-cylindrical mould cavities, an alternative dimension to the diameter may be chosen, for example the maximum width of the mould cavity in a perpendicular or a longitudinal direction. In some embodiments of the invention, the thickness of the wall sections may be chosen in dependence upon the desired structural and/or thermal transfer properties of the mould. For example, the channels may need to be a certain dimension to carry sufficient heat transfer fluid, and the thickness of the wall sections either side of the channels may need to be a minimum thickness to provide strength or may need to be less than a maximum thickness to increase the rate of thermal transfer. Generally speaking, in many embodiments the thickness of the wall sections will be a maximum of around 150 mm, 100 mm, 60 mm, 50 mm, 30 mm, 25 mm, 10 mm or 5 mm. The thickness of the wall sections may be within a range of these dimensions.

The first mould 2 is closed at one end by a first end wall section 12 and the second mould 3 is closed at one end by a second end wall section 14. The first and second end wall sections 12, 14 extend normal to the central axis 4, are generally annular in shape for a circular component, and respectively define a first end bore 16 and a second end bore 18. The end bores 16, 18 allow objects and fluids to pass into and out of the mould cavity 8. The first and second moulds 2, 3 further comprise a plurality of channels 20 for receiving a heat transfer fluid or fluids. The channels 20 extend parallel to the central axis 4 along the cylindrical wall sections 9, 10 in the vicinity of the mould surfaces 5, 6. The channels 20 of the first mould 2 are aligned with the channels 20 of the second mould 3 and extend from an inlet port 22 formed by the first mould surface 5 of the first mould 2 to an outlet port 24 formed by the second mould surface 6 of the second mould 3. Figure 2 is a plan view of the first mould 2 facing towards the first end wall section 12. As shown in Figure 2, the channels 20 are arranged at a regular pitch distance in a circumferential pattern surrounding the central axis 4. However, in alternative embodiments the pitch may be irregular, for example in dependence upon the shape of the mould or the component and/or for additional thermal agility as may be required.

With reference to Figure 3, during use, when a user wishes to create a composite component using the mould assembly 1, a lay-up material 26 (i.e. an unformed composite material) in the form of a pre-impregnated fibre textile or suitable alternative is inserted into the mould cavity 8 via one of the end bores 16, 18. Alternatively, the mould 1 may be assembled around the lay-up material 26 whilst the lay-up material 26 remains stationary (e.g. the lay-up material may be provided as part of a cartridge around which the mould assembly 1 is assembled, the cartridge may also comprise a compression device as discussed herein). In some embodiments, the lay-up material 26 may be heated before being inserted into the mould cavity 8 or the mould assembly 1 being assembled around it.

The lay-up material 26 comprises lengths of fibre combined into strings, each string being coated with a layer of polymer and woven into a tubular lattice. Alternatively the lay-up material 26 may comprise substantially any suitable material for composite moulding, for example a matted, non-woven, sheet of fibre and polymer strands or the like. The lay-up material 26 is flexible, and in some cases can easily be deformed to pass through the end bores 16, 18. A compression device in the form of an inflatable bladder 27 is passed into the mould cavity 8 via one of the end bores 16, 18 and arranged within the centre of the lay-up material 26 (in practice, the lay-up material 26 may be arranged upon the inflatable bladder 27 outside of the mould assembly 1 and placed into the mould cavity 8 in a single action before assembling the mould sections 2, 3 into a closed mould). The inflatable bladder 27 comprises a deformable membrane defining an expandable interior. The interior of the inflatable bladder 27 is mechanically and fluidly connected to a pump (not shown) for controlling inflation and deflation of the bladder 27. In Figure 3, the lay-up material 26 and the bladder 27 are shown in a preforming configuration (i.e. before expansion of the bladder 27).

With reference to Figure 4, the inflatable bladder 27 is inflated to push the lay-up material 26 outwards and force it into contact with the mould surfaces 5, 6 such that the lay-up material 26 and the bladder 27 are in a forming configuration. Because the lay-up material 26 is in contact with the mould surfaces 5, 6, the lay-up material 26 will substantially conform to the shape of the mould surfaces 5, 6 and therefore substantially take on the shape of the component to be made On practice, the shape of the mould cavity may differ slightly from the shape of the component to take into account thermal contraction, springback and other characteristics of the composite material and finished component form). The inflatable bladder 27 is sized and shaped such that when it is in its expanded state it does not contact the first or second end wall sections 12, 14. When the inflatable bladder 27 is in its expanded state, it defines a first manifold region 28 between the first end wall section 12 and the bladder 27 and a second manifold region 29 between the second end wall section 14 and the bladder 27. The first manifold region 28 permits fluid communication from the first end bore 16 to the inlet ports 22 and the second manifold region 29 permits fluid communication from the outlet ports 24 to the second end bore 18. In another embodiment the bladder 27 is sealed with a fitting that enables connection to the pump (not shown) and inflation of the bladder 27 such that it is constrained within the mould cavity 8. In such embodiments the manifold regions 28, 29 may be either integral to or additional to the end wall sections 12, 14. Additionally the bladder 27 can be open-ended and sealed at both ends with a fitting that enables connection to the pump (not shown) and inflation of the bladder 27 such that it is constrained within the mould cavity 8.

Once the inflatable bladder 27 has expanded, heat transfer fluid is supplied to the channels 20. Alternatively, the heat transfer fluid may be supplied to the channels 20 before or during expansion of the inflatable bladder 27. The heat transfer fluid may be supplied at the elevated temperature, or may be supplied at a lower temperature and then heated before, during or after expansion of the bladder 27. As shown by the arrows in Figure 4, the heat transfer fluid enters the mould cavity 8 via the first end bore 16 through an annular region defined between a stem 30 of the inflatable bladder 27 or a bladder sealing fitting and the first end wall section 12. The heat transfer fluid travels radially outwards relative to the central axis 4 through the first manifold region 28 and enters the channels 20 via the inlet ports 22. The channels 20 carry the heat transfer fluid along the cylindrical wall sections 9, 10, in the vicinity of the mould surfaces 5, 6, and into the second manifold region 29 via the outlet ports 24. The heat transfer fluid is then finally removed from the mould cavity 8 via the second end bore 18. The first and second moulds 2, 3 may include sealing and/or connection features to join the first and second end bores 16, 18 to a delivery device (e.g. a pipe network) for supplying the heat transfer fluid.

During moulding, the heat transfer fluid is supplied at an elevated temperature that is sufficiently high to melt the polymer material coating, surrounding, or co-mingled with the strings of fibres in the lay-up material 26. In some embodiments the heat transfer fluid may only be supplied once the lay-up material 26 is in place, whereas in other embodiments the heat transfer fluid may be supplied before the lay-up material 26 is placed within the mould assembly 1, so that the moulds 2, 3 are already warm. Further still, the heat transfer fluid may have partially warmed the moulds 2, 3 before the lay-up material 26 is introduced to the mould assembly 1, so that the length of time taken to get the mould 2, 3 up to temperature is reduced. It will be appreciated that the temperature of the heat transfer fluid must be sufficiently high that enough heat to cause melting of the polymer within the lay-up material 26 is transferred out of the heat transfer fluid to the moulds 2, 3 via the channels 20 and then subsequently transferred from the moulds 2, 3 to the lay-up material 26 via the mould surfaces 5, 6. The temperature of the heat transfer fluid will therefore be dependent upon the melting temperature of the polymer within the lay-up material 26 and will vary depending upon the type of polymer chosen. In some embodiments, the temperature of the heat transfer fluid will be slightly above the melting temperature of the lay-up material 26 polymer, so as to raise the temperature of the polymer in the lay-up material 26 to a state where it becomes sufficiently viscous to flow and enable the lay-up material 26 to take up the shape of the mould cavity 8 such that the component can be adequately formed. As such, the temperature of the heat transfer fluid may be chosen based on the rheological properties of the polymer within the lay-up material 26. For most polymer materials the temperature of the heat transfer fluid can be expected to be in the range of around 50 °C to around 450 °C, preferably within the range of around 100 °C to around 400 °C, or 150°C to around 350 °C, or 200 °C to around 300 °C, or around 250 °C. In some embodiments, the temperature of the heat transfer fluid may be +/-10°C, +/-20 °C, +/-30°C, or +/-50 °C relative to the melting temperature of the lay-up material 26. Further still, the temperature of the heat transfer fluid may be +/- 1 %, +/-2 %, +/-5 %, +/-10 or+/-25 % of the melting temperature of the lay-up material 26 polymer.

In alternative embodiments one or more of the channels 20 may comprise a plurality of small through holes that permit fluid communication with the mould cavity 8 through the cylindrical wall sections 9, 10. It will be appreciated that the lay-up material 26 in the unformed state will be porous and therefore heat transfer fluid can flow into the lay-up material 26 to more efficiently raise the temperature of the lay-up material. In such embodiments, the through holes may be supplied by a dedicated channel 20 and the moulds 2, 3 may comprise additional channels 20 that do not comprise through holes. The channels 20 comprising through holes may be supplied with heat transfer fluid independently of the channels 20 with no through holes and/or may be controlled independently of the channels 20 with no through holes. In alternative embodiments, one or more of the channels 20 may comprise a plurality of microbores which pass close to the mould surfaces 5, 6 but do not penetrate the mould surfaces 5, 6 to provide enhanced heat transfer.

The heat transfer fluid may be any suitable fluid, for example air or water. In some embodiments, the heat transfer fluid is heated using a heating device and delivered to the mould assembly 1 at a desired temperature. For example the heat transfer fluid can be heated by an apparatus comprising electrical heating element or the like and the temperature of the heat transfer fluid can be controlled using a PID controller. Furthermore, the heat transfer fluid may be selected based upon physical properties, such as a phase-change temperature, heat capacity, compressibility, viscosity at a desired temperature or the like.

In the present embodiment only the moulds 2, 3 are heated and/or cooled by the heat transfer fluid. However in alternative embodiments in addition to the moulds 2, 3 the compression device (e.g. the inflatable bladder 27 or another device as discussed below) may also be heated. The compression device may be heated and/or cooled by the same heat transfer fluid as the moulds 2, 3, or may be heated and/or cooled by a different heat transfer fluid. The compression device and the moulds 2, 3 may be fluidly arranged in series such that heat transfer fluid first passes through one then the other.

For example, the inflatable bladder 27 may comprise a pressure regulating outlet valve to control the internal pressure of the bladder 27, and heat transfer fluid vented through the valve may be fed to the channels 20 of the moulds 2, 3. In further embodiments an additional heat transfer fluid may be introduced between the moulds 2, 3 and the compression device in order to create a temperature difference between the heat transfer fluid in the channels 20 of the moulds 2, 3 and the heat transfer fluid in the compression device. This may provide a controlled temperature gradient over the lay-up material 26.

When the polymer within the lay-up material 26 melts, the polymer wets the fibres in a liquid fashion to form a single matrix of polymer encapsulating the fibres. Once the polymer has melted, the temperature of the heat transfer fluid is then reduced such that the heat transfer fluid begins to remove heat from the melted polymer matrix, causing the polymer matrix to consolidate and thereby form the component. When the component has consolidated, the bladder 27 is deflated. Once the component has cooled down to a safe handling temperature, the first and second moulds 2, 3 are separated along the central axis 4 and the component removed.

Because the heat transfer fluid in the channels 20 heats the moulds 2, 3 from within, the mould assembly 1 does not need to be placed in an oven for heating. Instead, all that is required is a heat source for the heat transfer fluid. Furthermore, because the thicknesses of the moulds 2, 3 are relatively thin in comparison to their widths and because the moulds 2, 3 generally conform to the shape of the component being made, the moulds 2, 3 have a relatively small thermal mass. As such, the amount of energy required to raise the mould surfaces 5, 6 to the desired temperature will be much less than the energy required to heat the entire internal volume of an oven and the contents within, therefore the use of internal heating channels the conformal geometry of the moulds 2, 3 relative to the component being made saves energy.

Furthermore, because no oven is required, the mould assembly 1 can be used to create components of an impractical size or shape that would not be able to fit in a standard commercial or industrial oven. Therefore, the mould assembly 1 could be used to manufacture extremely large components, such as wind turbine blades, pylons, aircraft wings, lamp posts, signage, bollards, street furniture or the like in an integral fashion where it would previously have been necessary to assemble such products in sections. The use of the mould assembly 1 therefore opens up the possibility of manufacturing large components monolithically and using lightweight high-strength composite materials where this would previously not have been possible. Furthermore, the mould assembly 1 could be used in a continuous extrusion process in which a continuous braid or sequence of lay-up material 26 is formed into desired cross-sectional profile in a continuous manner. Furthermore the mould assembly 1 could consist of a number of mould sections of different and/or irregular shape and geometry to manufacture variable shape and geometry components monolithically and using lightweight high-strength composite materials where this would previously not have been possible or prohibitively expensive.

In another embodiment the tool assembly 1 can be used for a resin transfer moulding process whereby the bladder 27 is replaced by a matched form internal component (not shown) so as to make a cavity between itself and the moulds 2, 3 surfaces 5, 6. In this embodiment dry fibre is laid onto the matched form internal component (not shown) prior to closing the mould sections 2, 3 and a resin transfer mechanism (not shown) attached to pump resin into the cavity. The heating of the moulds 2, 3 assists the resin transfer and curing processes, and in a similar manner heating the matched form internal component (not shown) further assists the process. The transfer of the resin into the cavity between the moulds 2, 3 internal surfaces and the matched form internal component (not shown) is completed and time allowed for the resin to cure. Once this has been achieved the mould temperature is reduced and mould assembly 1 opened to remove the component being made and if required extract the matched form internal component (not shown). In a further embodiment the matched form internal component (not shown) can be left within the component being made to support its function.

Additionally the matched form internal component (not shown) could be heated and cooled by a heat transfer fluid and a suitable channel 20, or a chamber similar to an inflated bladder 27.

Figure 6 is a schematic diagram of a system 40 for manufacturing a composite component using the mould assembly 1 of the first embodiment. The system 40 comprises the mould assembly 1, a heat regulating device 42, a fluid delivery and return device 44, and a compression device 46. The heat regulating device 42 is configured to provide heat to the heat transfer fluid and to control the temperature of the heat transfer fluid to a predetermined value. The heat regulating device 42 may be any suitable device, for example a boiler equipped with a PI D control. The fluid delivery and return device 44 comprises a network of conduits for delivering heat transfer fluid that has been controlled to a particular temperature to the mould assembly 1, and for returning heat transfer fluid that has passed through the mould assembly 1 to the heat regulating device 42. In alternative embodiments, the heat transfer fluid that has passed through the mould assembly 1 may simply be vented to atmosphere or disposed of down a drain. However, as previously discussed the heat transfer fluid could be "recycled" and passed into or received from the compression device. The fluid delivery and return device may comprise a suitable control means for controlling the pressure and/or flow rate of the fluid. This includes for example throttles, pressure relief valves or the like. The compression device 46 comprises the inflatable bladder 27, a pump 48 and a conduit 50 fluidly connecting the pump 48 to the bladder 27.

Mould Geometries It will be appreciated that the precise shape and size of the mould surfaces 5, 6 is dependent upon the geometry of the component to be manufactured and will therefore vary component-to-component. As such, in alternative embodiments the mould surfaces 5, 6 may have substantially any suitable shape and size. The example shown in Figures 1 to 4 is merely a simplification to illustrate the working principals of the invention. Furthermore, although the first and second moulds 2, 3 are separable along the central axis 4, in alternative embodiments the first and second moulds 2, 3 may be separable in any other direction. For example, the first and second moulds may be separable in a direction perpendicular to the central axis 4 (i.e. in the manner of an "Easter egg"). Furthermore, although two moulds 2, 3 are illustrated, it will be appreciated that in alternative embodiments any suitable number of moulds may be used. For example, one, two, three or more moulds can be assembled together to define a single mould cavity 8. That is to say, a number of individual moulds can be manufactured and then assembled together in a modular fashion to define the mould cavity 8.

The illustrated mould assembly 1 is a closed mould, as it encapsulates the component on all sides. This is generally suitable for components in which the convexly shaped or outer surfaces require a good or highly controllable surface finish, for example struts or the like. It will be appreciated that in some embodiments the first and second mould surfaces 5, 6 may be used to manufacture the "A" surfaces of the component, the "A" surfaces being the higher-quality or smother sides of the component. By contrast, the surface finish provided by the compression device (for example, the bladder 27) may be rougher and less controllable, such that the compression device is used to manufacture lower-quality, less controllable and/or rougher sides of the components, which may be referred to as the "B" surfaces. Such components may be referred to as "A" and "B" surfaced components.

In alternative embodiments the mould assembly 1 may be an open mould. Open moulds are open on at least one side and are generally suitable for manufacturing concavely shaped components such as vehicle body panels, enclosures, bath tubs or the like. One such example is shown in Figure 5 which depicts a second embodiment of a mould assembly 30 according to the invention comprising a mould 31 having a channel 32 (or plurality of channels) and defining a mould surface 34 upon which a lay-up material 36 has been placed. The mould 31 defines a generally bowl-shaped concave interior so as to produce a bowl-shaped component.

In the first and second embodiments the walls of the moulds define substantially constant thicknesses (put another way, the thicknesses of the moulds are generally or substantially uniform). However, in alternative embodiments, the thickness of the mould may be varied in dependence upon the geometry of the component. For example, the component may have a wall thickness that varies along its length. In such cases, thinner sections of the lay-up material may reach their forming temperature faster than the thicker sections, and may be cooled below the forming temperature (to cause the material to set) faster than the thicker sections. As such, it may be beneficial to provide the mould with a correspondingly thicker wall section in the vicinity of the thin sections of the component so as to provide slower heating and/or cooling time in this region (the larger thickness of the mould taking a longer time to heat up or cool down in comparison to thinner sections of the mould). Likewise, thicker sections of the component will take longer to heat up or cool down and therefore it may be beneficial to reduce the thickness of the mould in these regions so as to provide faster heating and/or cooling. In yet further alternatives, the position of the channels can be chosen so that the channels are more closely bunched in the vicinity of thicker regions of the component, and more sparsely spaced in the vicinity of the thinner regions of the component. In general, the thickness of the walls or any other geometry of the mould may be adjusted to provide different thermal properties in a particular region of the mould in dependence upon the geometry of the component being made. For example, the moulds 2, 3 may not be constant in cross-section and may be varied. The moulds 2, 3 may be tapered.

Although the moulds 2, 3 define generally cylindrical wall sections 9, 10 it will be appreciated that, in practice, it may be necessary to provide the cylindrical wall sections 9, 10 with a draft angle to aid the extraction of the component from the moulds 2, 3. In some embodiments, the moulds 2, 3 may comprise a longitudinally extending slot configured to provide compliance and allow the geometry of the mould cavity to be adjusted. Further still, although not shown in the figures, if the length of the component is to be made longer an additional mould may be introduced between the first and second moulds 2, 3. This additional mould may be generally tubular in shape, and open at both longitudinal ends to mate with the first and second moulds 2, 3. The additional mould may comprise a longitudinally extending slot running the entire length of the additional mould, such that the cross-section of the additional mould relative to the central axis is generally c-shaped. This c-shaped cross section provides compliance to allow the geometry of the mould cavity to be slightly adjusted, enabling the geometry of the component to be made to be adjusted and/or to facilitate removal of the component from the mould assembly 1 once formed. In such cases a wedge, shim or packing pieces may be inserted in the slot to complete the internal geometry of the mould assembly 1.

Channel Geometries In the first embodiment, the inflatable bladder expands to define first and second manifold regions 28, 29. However, it will be appreciated that in alternative embodiments, the channels 20 may join one another via one or more manifolds defined within the body of the moulds 2, 3 themselves. For example, the manifold regions 28, 29 may be defined within the end wall sections 12, 14 and therefore a single inlet port and a single outlet port may be used to feed all of the channels 20. Furthermore, although the embodiment of Figures 1 to 4 comprises a plurality of channels 20, it will be appreciated that in alternative embodiments a single channel may be provided. The single channel can be shaped to define a boustrophedonic (i.e. back and forth) or alternatingly "zig-zagged" path from a single inlet port to a single outlet port.

Where a plurality of channels is used, the channels may define a common or concordant geometrical relationship relative to one another along sections of the mould assembly. Such a concordant geometrical relationship encompasses the presence of a particular characteristic in the geometry of the channels, and in particular the size, shape or path of the channels. For example, the channels can be arranged parallel to one another. The channels may be offset from one another by an offset distance in a first direction (for example, in a circumferential direction about a central axis) and the channels may extend along a second direction (for example, along the central axis) in which the offset distance is maintained. The channels may extend helically and each channel may define the same helix angle. The channels may begin and/or terminate at common points along a longitudinal axis of the mould assembly. The channels may converge or diverge relative to a common origin, or may define a series of arcs or different radiuses about a common origin. The channels may define the same cross-sectional shape, which may be for example circular, elliptical, rectangular or any other suitable shape. The channels may define the same cross-sectional size in a direction normal to the direction of fluid flow through the channels. The channels may be arranged in a sequence, each channel in the sequence having a different size, shape and/or path, and the sequence may be repeated one or more times. Where a single channel is used (rather than a plurality of channels), portions of the channel may define a concordant geometrical relationship with other portions of the channel. For example, where the channels define a boustrophedonic path. By ensuring that the channels or portions of the channels define concordant geometries, it can be ensured that the channels are able to transfer heat into and out of the mould assembly evenly, and avoid the occurrence of undesired hot or cold spots. Alternatively, the channels may have non-concordant geometries, or have sections of non-concordant geometries. In some embodiments the channels may define different sizes, cross-sections or other geometries that vary along the length of the channel, and adjacent channels may define concordant or non-concordant relative geometries in this regard.

With reference to Figure 3, the channels 20 of the first embodiment are arranged circumferentially around the central axis 4 at a common radius. Furthermore, the channels 20 are positioned radially closer to the mould surfaces 5, 6 than the outer surfaces 7, 11. By positioning the channels 20 closer to the mould surfaces 5, 6, this ensures faster heat transfer to the mould surfaces. Additionally, this means that the increased thickness of the radially outer part of the walls 9, 10 is able to provide sufficient strength to support the moulds 2, 3. It will be appreciated that in alternative embodiments the channels 20 could be positioned at any position between the mould surfaces 5, 6 and the outer surfaces 7, 11. Furthermore, in alternative embodiments the channels 20 may be placed at different spacings from the mould surfaces 5, 6. For example, the moulds may comprise a first ring of channels circumferentially spaced apart from one another along a first pitch circle, and a second ring of channels circumferentially spaced apart from one another along a second pitch circle having a diameter larger or smaller than the first pitch circle. The positions of the channels 20 of the first and second rings may be circumferentially offset from one another, for example such that the channels are arranged in an alternating or tessellated fashion.

In the embodiment of Figures 1 to 4, the heat transfer fluid is carried through all of the channels 20 from one end of the mould assembly 1 to the other. However, it will be appreciated that in alternative embodiments the mould assembly 1 may comprise substantially any number of separate networks of channels 20 that carry heat transfer fluid in different directions or that carry different heat transfer fluids. For example, the mould assembly 1 may define a first set of channels 20 that are used to receive a heating fluid for heating the mould assembly 1, and may further comprise a second set of channels 20 that are used for receiving a cooling fluid for cooling the mould assembly 1. The two networks of channels 20 can be arranged in an alternating or tessellated fashion within the body of the moulds 2, 3. The use of two networks of channels 20 may enable faster temperature changes. Alternatively, the two networks of channels 20 could carry heat transfer fluid at elevated but different temperatures. This enables different amounts of heat to be transferred to different sections of the moulds 2, 3, and is useful for example where the lay-up material 26 is not uniform and is thicker in certain areas (such thicker areas requiring more heat to melt the polymer or cure a resin, and therefore higher temperature heat transfer fluid or a faster heat transfer fluid flow rate is achieved). The two networks of channels 20 may carry the same or different heat transfer fluids. For example, nitrogen maybe used to cool the moulds 2, 3 and air may be used to heat the moulds 2, 3. Additionally more than two networks of channels may be provided in moulds 2, 3 and/or the compression device, or insert 38, or the matched form internal component (not shown) for resin transfer moulding In the embodiments shown, heat transfer fluid enters and leaves the channels via separate inlet and outlet ports. However it will be appreciated that in alternative embodiments of the invention a single port may be provided functioning as both the inlet and the outlet port. Additionally or alternatively, a pressure relief valve may be provided to selectively vent fluid from the channel(s) if the pressure of the fluid rises above a predetermined threshold.

Compression Device In the example of Figures 1 to 4, the compression device is an inflatable bladder 27.

However, it will be appreciated that in alternative embodiments, any suitable compression device may be provided for causing the lay-up material to contact the mould surfaces. One such example is shown in Figure 5, in which a an insert 38 having an inversely corresponding shape to the mould 31 is inserted within the central portion of the U-shaped mould 31 to cause the lay-up material 36 to be compressed against the mould surface 34 and thereby take on the shape of the mould surface 34. The insert 38 may be urged against the lay-up material 36 using any suitable means, including for example mechanical, thermal, electrical, pneumatic, or hydraulic actuation, or electromagnetic attraction / repulsion. In the example shown in Figure 5, the insert 38 comprises a magnetic component 39 and the compression device further comprises an electromagnet 41 configured to magnetically attract the magnetic component 39 of the insert 38 so as to compress the lay-up material 34 therebetween.

In a further alternative (not shown), the insert 38 may be replaced by a deformable membrane attached to the perimeter of the open side of the mould 31. The area between the membrane and the mould 31 which defines the mould cavity can then be subjected to vacuum pressure to cause the membrane to deform and compress the lay-up material 36 against the mould surface 34. In general terms, by providing a compression device it can be ensured that the lay-up material takes on the desired shape. Furthermore, the use of a compression device enables more precise control of the pressure that the lay-up material is subjected to during the moulding process.

In another alternative the compression device may contain a channel 20 or a plurality of channels for heating and cooling as in the moulds 2, 3 of the first embodiment.

Types of Lay-Up In the examples above, the lay-up materials 26, 36 are pre-impregnated polymer-fibre textiles. However, it will be appreciated that substantially any suitable lay-up material may be used. For example, the lay-up material may comprise an uncoated woven fibre and a liquid polymer or resin that is injected into the mould cavity. The mould assembly may be heated using the channels and the heat transfer fluid to keep the lay-up polymer in a liquid state or cure a resin, and the temperature of the heat transfer fluid can be controlled to cool the polymer so that it sets hard. In one embodiment, the lay-up material 26 may be a mat of comingled polymer and fibre strands. Further still, the invention may be applied to any suitable moulding process, for example using polymer only without the presence of fibre strands.

Mould Materials A mould according to the present invention can in principal be made from substantially any suitable material. Preferably, the mould is made from a thermally conductive material so as to provide heat transfer communication between the channel(s) and the mould surface(s). However, due to the relatively thin nature of the walls of the moulds 2, 3 the thermal conductivity of the mould material does not need to be exceptionally high. It has been found that many materials that are suitable for manufacture using an additive manufacture process provide sufficient thermal conductivity that enough heat can be transferred into the moulds 2, 3. Furthermore, the mould material must be able to withstand the temperatures applied by the heat transfer fluid when it is used for manufacturing the desired components. That is to say, provided that the mould material should not melt, deform, or change shape in a manner that would distort the geometry of the finished component outside of an acceptable limit. Suitable mould materials include metal, plastic, ceramic or the like.

Preferably the mould material is an X-ray transparent material. X-ray transparent materials are materials that exhibit at least some transmissivity to electromagnetic radiation in the range of 0.01 nm to 10 nm. Preferably, the mould material is able to transmit at least 80 %, more preferably 90 %, and most preferably 95 % of incident X-ray radiation. Suitable x-ray transparent materials include polymers. An example of a suitable X-ray transparent material is Somos® PerFORM.

Where an X-ray transparent material is used for the mould, the mould may be placed within an X-ray spectroscopy machine during the process of forming the components, for example as part of a production line. The X-ray spectroscopy machine can monitor the mechanical properties of the lay-up material, for example movement of the fibres during moulding, in real time (or pseudo real time) as the mould is heated. The use of an X-ray transparent material and an X-ray spectroscopy machine therefore permits the real time (or pseudo real time) detection of defects within the composite material and the forming of it as it is being moulded, which can be used to adjust and improve the input parameters of the moulding operation (e.g. controlled temperature ramp-up, soak time, pressure, mould geometry, reducing thermal shock or the like). The above notwithstanding, materials that transmit less than 80 % of incident X-ray radiation may be suitable, however the definition of any defects visible by X-ray will be lower.

Preferably the mould is made from a material having some degree of elastic flexibility whilst remaining rigid enough so that the shape of the component cannot be deformed outside of an acceptable limit. As such, the mould is resiliently deformable such that it permits adjustment to the mould cavity by flexing the mould by a small amount. For example, the mould may be provided with a slot, and a shim can be provided in the slot to cause the mould to flex outwardly to slightly increase the size of the component being made. Additionally, a resiliently deformable mould material may assist with removing the finished component from the mould. Put another way, a flexible mould material adds a degree of compliance to the mould to better control the dimensions of the finished component. Examples of suitably flexible materials are those which are able to withstand at least around 0.1 To, 0.5 Wo, 1 c/o, 2 % or 5 c/o elongation and/or compression.

Additive Manufacturing In principle, the moulds 2, 3 can be made via substantially any suitable manufacturing process. For example, the moulds could be subtractively machined from a workpiece or cast. However, in general it is preferable that the moulds 2, 3 are made via additive manufacturing. By manufacturing the moulds 2, 3 using an additive manufacturing process it is possible to achieve geometries that would otherwise not be possible using alternative methods or that would be prohibitively expensive to make. For example, additive manufacturing allows a large number of relatively small channels 20 to be included within the moulds 2, 3 and the channels 20 can include features that are not possible to machine, such as twists, bends, elbows, internal turbulators, or the like.

Furthermore, the use of additive manufacturing means that it is not necessary to produce a bespoke tool for manufacturing each mould. As such, a mould can be produced quickly and cheaply for manufacturing a relatively small run of components. Alternatively, the moulds 2, 3 can be used for high volume production runs (i.e. used a relatively large number of times). When the moulds 2, 3 are used in a high volume production run, it is preferable to coat the first and second mould surfaces 5, 6 with a protective layer or layers to prevent damage to the mould. Similarly this could be applied to the mould surfaces of the compression device. In this context it will be appreciated that a protective layer may require the use of a chemical interface to bound a hard coating to the moulds 2, 3 to form a protective outer skin, and is distinct from an internal "layer" of the moulds 2, 3, that result from their production using an additive manufacturing process.

As used herein, "additive manufacturing" refers generally to manufacturing processes wherein successive layers of material(s) are provided on each other to "build-up" layer-by-layer or "additively fabricate", a three-dimensional mould. This is compared to some subtractive manufacturing methods (such as milling or drilling), wherein material is successively removed to fabricate the part. The successive layers generally fuse together to form a monolithic mould which may have a variety of integral sub-moulds.

Additive manufacturing methods described herein enable manufacture to any suitable size and shape with various features which may not have been possible using prior manufacturing methods. Additive manufacturing can create complex geometries without the use of any sort of tools, moulds or fixtures, and with little or no waste material. Instead of machining moulds from solid billets of plastic or metal, much of which would be cut away and discarded, in some additive manufacturing processes the only material used is what is required to shape the part. However, in some additive manufacturing processes a support structure of the same or a different material to the part may also be required. In other additive manufacturing processes multiple materials and combinations of materials are possible.

Suitable additive manufacturing techniques in accordance with the present disclosure include, for example, Fused Deposition Modelling (FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjets and laserjets, Stereolithography (SLA), Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), Electron Beam Additive Manufacturing (EBAM), Laser Net Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), Digital Light Processing (DLP), Continuous Digital Light Processing (CDLP), Direct Selective Laser Melting (DSLM), Selective Laser Melting (SLM), Direct Metal Laser Melting (DMLM), Direct Metal Laser Sintering (DMLS), Material Jetting (MJ), Nano Particle Jetting (NPJ), Drop On Demand (DOD), Binder Jetting (BJ), Multi Jet Fusion (MJF), Laminated Object Manufacturing (LOM) and other known processes.

The additive manufacturing processes described herein may be used for forming the moulds 2, 3 using any suitable material. For example, the material may be plastic, metal, composite, concrete, ceramic, polymer, epoxy, photopolymer resin, or any other suitable material that may be in solid, liquid, powder, sheet material, wire, or any other suitable form or combinations thereof. More specifically, according to exemplary embodiments of the present subject matter, the additively manufactured parts (i.e. the moulds 2, 3) described herein may be formed in part, in whole, or in some combination of materials including but not limited to pure metals, nickel alloys, chrome alloys, titanium, titanium alloys, magnesium, magnesium alloys, aluminium, aluminium alloys, iron, iron alloys, stainless steel, and nickel or cobalt based superalloys (e.g., those available under the name Inconel() available from Special Metals Corporation). These materials are examples of materials suitable for use in additive manufacturing processes which may be suitable for the fabrication of examples described herein. Stainless steel, in particular grade 316, is a preferred material for use in manufacturing the moulds 2, 3 disclosed herein. In some embodiments a polymer skin may additionally be included surrounding the moulds by either additive or subtractive manufacturing. In some embodiments an outer skin may be manufactured additively from metal and an inner skin may be made additively from a polymer material.

As noted above, the additive manufacturing process disclosed herein allows a single mould to be formed from multiple materials. Thus, the examples described herein may be formed from any suitable mixtures of the above materials. For example, a mould may include multiple layers, segments, or parts that are formed using different materials, processes, and/or on different additive manufacturing machines. In this manner, moulds may be constructed which have different materials and material properties for meeting the demands of any particular application. In addition, although the moulds described herein are constructed entirely by additive manufacturing processes, it should be appreciated that in alternate embodiments, all or a portion of these moulds may be formed via casting, machining, and/or any other suitable manufacturing process. Indeed, any suitable combination of materials and manufacturing methods may be used to form these moulds.

Additive manufacturing processes typically fabricate moulds based on three-dimensional (3D) information, for example a three-dimensional computer model (or design file), of the mould.

Accordingly, examples described herein not only include products or moulds as described herein, but also methods of manufacturing such products or moulds via additive manufacturing and computer software, firmware or hardware for controlling the manufacture of such products via additive manufacturing.

The structure of one or more parts of the product may be represented digitally in the form of a design file. A design file, or computer aided design (CAD) file, is a configuration file that encodes one or more of the surface or volumetric configuration of the shape of the product. That is, a design file represents the geometrical arrangement or shape of the product. The CAD file may be created and/or arranged by a user, or alternatively may be created and/or arranged computationally using a small number of user inputs. For example, the CAD file may be created generatively, in which the geometry of the final component is used as an input to a computational process which automatically computes and determines the shape, geometry (whether internal or external), configuration, and composition of the mould in dependence upon geometrical and/or thermal properties of the moulding process.

Design files can take any now known or later developed file format. For example, design files may be in the Stereolithography or "Standard Tessellation Language" (.stl) format which was created for stereolithography CAD programs of 3D Systems, or the Additive Manufacturing File (.amf) format, which is an American Society of Mechanical Engineers (ASME) standard that is an extensible markup-language (XML) based format designed to allow any CAD software to describe the shape and composition of any three-dimensional object to be fabricated on any additive manufacturing printer.

Further examples of design file formats include AutoCAD (.dwg) files, Blender (.blend) files, Parasolid (.x_t) files, 3D Manufacturing Format (.3mf) files, Autodesk (.3ds) files, Collada (.dae) files and Wavefront (.obj) files, although many other file formats exist.

Design files can be produced using modelling (e.g. CAD modelling) software and/or through scanning the surface of a product to measure the surface configuration of the product.

Once obtained, a design file may be converted into a set of computer executable instructions that, once executed by a processer, cause the processor to control an additive manufacturing apparatus to produce a product according to the geometrical arrangement specified in the design file. The conversion may convert the design file into slices or layers that are to be formed sequentially by the additive manufacturing apparatus. The instructions (otherwise known as geometric code or "G-code") may be calibrated to the specific additive manufacturing apparatus and may specify the precise location and amount of material that is to be formed at each stage in the manufacturing process. As discussed above, the formation may be through deposition, through sintering, or through any other form of additive manufacturing method. Once formed, the mould may be subsequently processed using subtractive manufacturing to include additional features or to make any necessary adjustments to the geometry.

The code or instructions may be translated between different formats, converted into a set of data signals and transmitted, received as a set of data signals and converted to code, stored, etc., as necessary. The instructions may be an input to the additive manufacturing system and may come from a part designer, an intellectual property (IP) provider, a design company, the operator or owner of the additive manufacturing system, or from other sources. An additive manufacturing system may execute the instructions to fabricate the product using any of the technologies or methods disclosed herein.

Design files or computer executable instructions may be stored in a (transitory or non-transitory) computer readable storage medium (e.g., memory, storage system, etc.) storing code, or computer readable instructions, representative of the product to be produced. As noted, the code or computer readable instructions defining the product that can be used to physically generate the object, upon execution of the code or instructions by an additive manufacturing system. For example, the instructions may include a precisely defined 3D model of the product and can be generated from any of a large variety of well-known computer aided design (CAD) software systems such as AutoCADO, SolidWorks®, TurboCADO, DesignCAD 3D Max, etc. Alternatively, a model or prototype of the mould may be scanned to determine the three-dimensional information of the mould.

Accordingly, by controlling an additive manufacturing apparatus according to the computer executable instructions, the additive manufacturing apparatus can be instructed to print out one or more parts of the mould. These can be printed either in assembled or unassembled form. For instance, different sections of the product may be printed separately (as a kit of unassembled parts) and then subsequently assembled. Alternatively, the different parts may be printed in assembled form.

In light of the above, embodiments include methods of manufacture via additive manufacturing. This includes the steps of obtaining a design file representing the product and instructing an additive manufacturing apparatus to manufacture the product in assembled or unassembled form according to the design file. The additive manufacturing apparatus may include a processor that is configured to automatically convert the design file into computer executable instructions for controlling the manufacture of the product. In these embodiments, the design file itself can automatically cause the production of the product once input into the additive manufacturing device. Accordingly, in this embodiment, the design file itself may be considered computer executable instructions that cause the additive manufacturing apparatus to manufacture the product. Alternatively, the design file may be converted into instructions by an external computing system, with the resulting computer executable instructions being provided to the additive manufacturing device. In addition the steps required to convert a design file to executable instructions that cause the additive manufacturing apparatus to manufacture the product can be multiple.

Given the above, the design and manufacture of implementations of the subject matter and the operations described in this disclosure can be realized using digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. For instance, hardware may include processors, microprocessors, electronic circuitry, electronic components, integrated circuits, etc. Implementations of the subject matter described in this specification can be realized using one or more computer programs, i.e., one or more modules of computer program instructions, encoded on computer storage medium for execution by, or to control the operation of, data processing apparatus. Alternatively or in addition, the program instructions can be encoded on an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. A computer storage medium can be, or be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

Although additive manufacturing technology is described herein as enabling fabrication of complex objects by building objects point-by-point, layer-by-layer, typically in a vertical direction, other methods of fabrication are possible and within the scope of the present subject matter. For example, although the discussion herein refers to the addition of material to form successive layers, one skilled in the art will appreciate that the methods and structures disclosed herein may be practiced with any additive manufacturing technique or other manufacturing technology.

Claims

CLAIMS: 1. A mould (2, 3) for manufacturing a composite component, the mould comprising: a first surface (5, 6) defining at least part of a mould cavity (8) for receiving an unformed composite material (26); and at least one channel (20) for receiving a heat transfer fluid; wherein the mould (2, 3) is configured to provide heat transfer communication between the channel (20) and the first surface (5, 6) so as to form the composite material to the shape of the mould cavity (8).
2. A mould (2, 3) according to claim 1, wherein the mould (2, 3) is addifively manufactured.
3. A mould (2, 3) according to any preceding claim, wherein the mould (2, 3) comprises a plurality of channels (20).
4. A mould (2, 3) according to any preceding claim, wherein the plurality of channels (20) define a concordant geometrical relationship relative to one another along at least a portion of their lengths.
5. A mould (2, 3) according to any claim 4, wherein the concordant geometrical relationship is selected from the group comprising: (i) the channels (20) extending in parallel to one another; (ii) the channels (20) being offset from one another by an offset distance in a first direction and the channels (20) extending along a second direction in which the offset distance is maintained; (iii) the channels (20) extending helically wherein each channel (20) defines the same helix angle; (iv) each channel (20) defining a different radius of curvature about a common origin.
6. A mould (2, 3) according to any preceding claim, wherein the mould (2, 3) comprises a second surface (7, 11) on an opposite side of the mould (2, 3) to the mould cavity (8), and wherein the second surface (7, 11) defines a generally conformal geometry in relation to the first surface (5, 6).
7. A mould (2, 3) according to claim 6, wherein the channel positioned closer to the first surface (5, 6) than the second surface (7, 11).
8. A mould (2, 3) according to any preceding claim, wherein: the mould (2, 3) defines a longitudinal axis (4) and a thickness in a generally radial direction with respect to the longitudinal axis (4); the mould cavity (8) defines a width in a generally radial direction with respect to the longitudinal axis (4); and the thickness of the mould (2, 3) is less than around 30 % of the width (2, 3) of the mould cavity (8).
9. A mould (2, 3) according to claim 8, wherein the thickness of the mould (2, 3) is less than around 25 % of the width of the mould cavity (8), or preferably less than around 10%, 5 %, or 2.5 % of the width of the mould cavity (8).
10. A mould (2, 3) according to claim 8 or 9, wherein the thickness of at least a portion the mould (2, 3) is generally uniform.
11. A mould (2, 3) according to claim 8 or 9, wherein the thickness of the mould (2, 3) is varied in different regions of the mould (2, 3) in dependence upon the thickness of the unformed composite material (26).
12, A mould (2, 3) according to any preceding claim, wherein the mould (2, 3) comprises one or more through holes connecting the channel (20) and the first surface (5, 6) to provide fluid flow communication form the channels (20) to the mould cavity (8)-
13. A mould (2, 3) according to any preceding claim, wherein the mould (2, 3) is made from an X-ray transparent material.
14. A mould (2, 3) according to any preceding claim, wherein the mould (2, 3) is resiliently deformable to permit adjustments to the geometry of the mould cavity.
15. A mould (2, 3) according to any preceding claim, wherein the mould (2, 3) comprises an additively manufacturable material.
16. A mould (2, 3) according to any preceding claim, comprising a port for supplying and/or removing heat transfer fluid to and from the channel and an outlet port for removing heat transfer fluid from the channel.
17. A mould (2, 3) according to any preceding claim, wherein the first surface (5, 6) is coated with a protective layer.
18. A mould assembly (1) comprising a plurality of moulds (2, 3) according to any preceding claim.
19. A method of producing the mould (2, 3) of any preceding claim, the method comprising: obtaining an electronic file representing a geometry of the mould (2, 3); and controlling an additive manufacturing apparatus to manufacture the mould (2, 3) according to the geometry specified in the electronic file.
20. A system (40) for manufacturing a composite component, the system comprising: a mould (2, 3) according to any of claims 1 to 17 or a mould assembly according to claim 18; a heat regulating device (42) for controlling the temperature of the heat transfer fluid; and a fluid delivery device (44) for supplying heat transfer fluid to the channel (20).
21. A system (40) according to claim 20, further comprising a compression device (48) for exerting a compressive force upon the unformed composite material (26, 34) to form the composite material to the shape of the mould cavity (8).
22. A system (40) according to claim 21, wherein the compression device is configured to receive a heat transfer fluid for controlling the temperature of the compression device.
23. A system (40) according to claim 21 or 22, wherein the compression device (48) comprises: a deformable membrane (27); and a fluid pump (48), wherein the fluid pump (48) is configured to control the pressure on one or both sides of the membrane (27) to cause the membrane (27) to exert the compressive force on the unformed composite material (26).
24. A system (40) according to claim 23, wherein the membrane is an inflatable bladder (27) or a vacuum bag.
25. A system (40) according to claim 21 or 22, wherein the compression device (46) comprises an insert (38) configured to be received within the mould cavity (8). 15
26. A system (40) according to claim 21, wherein: the system further comprises an electromagnet (41); the insert comprises a magnetic component (39); and wherein activation of the electromagnet (41) causes the insert (38) to exert the compressive force on the unformed composite material (34).
27. A method of manufacturing a composite component, the method comprising: providing a mould (2, 3) according to any of claims 1 to 17 or a mould assembly according to claim 18; engaging an unformed composite material (26, 34) with the first surface (5, 6); and supplying a heat transfer fluid to the channel (20) to heat the unformed composite material (26, 34) via the first surface (5, 6) so as to form the composite material (25, 34) to the shape of the mould cavity (8).
28. A method according to claim 27, further comprising manufacturing the mould using an additive manufacture process.
29. A method according to claim 27 or 28, further comprising providing a compression device (48) and exerting a compressive force upon the unformed composite material (26, 34) via the compression device (48) to form the unformed composite material (26, 34) to the shape of the mould cavity (8).