GB2399049A

GB2399049A - Composite structural component and method

Info

Publication number: GB2399049A
Application number: GB0304964A
Authority: GB
Inventors: Clive John Chaplin
Original assignee: STOUR PREC TOOLS Ltd
Current assignee: STOUR PREC TOOLS Ltd
Priority date: 2003-03-05
Filing date: 2003-03-05
Publication date: 2004-09-08
Anticipated expiration: 2023-03-05
Also published as: GB0304964D0; GB2399049B

Abstract

A composite structural component (1) and method of manufacturing the composite structural component (1) comprising the steps of providing a core (29) of a first material and depositing a second material onto an outer surface of the first to form a sheath (31) of the second material. The second material has greater structural strength than the first material.

Description

COMPOSITE STRUCTURAL COMPONENT AND METHOD

The invention relates to composite structural components, and more particularly but not exclusively, to support fixtures. The invention also relates to a method for manufacturing composite structural components.

During the manufacturing or processing of an article, there is a range of support fixtures which are frequently required to position an article or tool at a particular precisely controlled location and/or orientation. Such support fixtures are, for example, robot welding fixtures, robotic material handling grippers, location fixtures, jigs, assembly fixtures, and structural frames and supports.

Computer-aided design is often used in order to determine the required dimensions for a new support fixture.

Current support fixtures are manufactured by means of fabricating and machining processes known to a person skilled in the art. The support fixtures are fabricated from, for example, metal. However, the production of support fixtures based on fabrication and machining means is time consuming and expensive. 1 i

There is a need for a support fixture that can be manufactured, cost effectively and relatively quickly, directly from a computer-aided design such that the support fixture not only has the required profile and dimensions but also has sufficient structural strength for the intended application.

It is therefore an object of the present invention to provide a composite structural component and a method of manufacture of the same which overcomes or minimises these problems.

According to one aspect of the present invention there is provided a composite structural component comprising a core of a first material and an outer sheath of a second material, wherein the second material has greater structural strength than the first material.

According to another aspect of the present invention there is provided a method of manufacturing a composite structural component comprising the steps of providing a core of a first material and depositing a second material onto an outer surface of the first to form a sheath of the second material, wherein the second material has greater structural strength than the first material. - 3 -

The first and second materials may be dissimilar.

The first material may comprise a sintered powder material or a plastics material, for example a cured photopolymer.

The first material may be manufactured by rapid prototyping means, for example by stereolithography means, selective laser sintering means or polyjet means.

The second material may be a metallic material, for example a thermally sprayable metallic material, preferably a zinc and/or aluminium alloy.

The composite structural component may comprise inserts, for example bush liners, threaded inserts, threaded inserts with locating spigots, threaded stud inserts, eccentric adjustable position location bushes, profiled inserts and mounting plates.

The inserts may be positioned to enable accurate location of the composite structural component in relation to a fixing surface, for example for the attachment of the composite structural component to a surface or the fixing of attachments to the composite structural component. - 4 -

The inserts may comprise means for being embedded into the sheath of the second material, for example a serrated surface may be provided which may be keyed to the second material.

The sheath of the second material may surround only a proportion of the first material.

The present invention therefore provides a lightweight, low cost composite structural component which may be used as a support fixture and which may be made by a combination of rapid prototyping and thermal spraying technologies.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a perspective view of one embodiment of a composite structural component according to the present invention; Figure 2 is a cross-sectional view along the line A-A of the composite structural component shown in Figure 1; Figure 3 is a perspective view of a first embodiment of an insert present in the composite structural component shown in Figures 1 and 2; Figure 4 is a perspective view of a second embodiment of an insert present in the composite structural component shown in Figures 1 and 2; Figure 5 is a perspective view of a third embodiment of an insert present in the composite structural component shown in Figures 1 and 2; Figure 6 is a perspective view of a core of the composite structural component shown in Figures 1 and 2; Figure 7 is an alternative perspective view of the core shown in Figure 6; Figure 8 is a perspective view of a second embodiment of a composite structural component according to the present invention; and Figure 9 is a cross-sectional view along the line B-B of the composite structural component shown in Figure 8. - 6

Figure 1 shows an embodiment of a composite structural component 1 according to the present invention comprising an elongate body 3 arranged in a substantially "Vn shaped configuration with a first longitudinal edge 5, a second longitudinal edge 7 and an apex 9. A substantially planar surface 11 is provided on the elongate body at a first end 13, substantially at a right angle to the longitudinal axis of the elongate body, and arranged to extend across the "V" shaped opening 15 of the elongate body. A second end 17 of the elongate body forms an open face of the "V" shaped opening of the elongate body. Provided centrally in a first side 19 of the "V" shaped elongate body is an aperture 21.

Inserts 23, 25, 27 are provided through the planar surface 11 in the region of, and longitudinal to, the first longitudinal edge 5, the second longitudinal edge 7 and the apex 9 of the elongate body 3. These inserts are used, for example, for the attachment of the component to a surface (not shown) or the fixing of attachments (not shown) to the component.

In Figure 2 it can be seen that the composite structural component according to the present invention comprises a core 29 of a first material, for example a plastics material, preferably a cured photopolymer, and an outer sheath 31 of a second material, for example a metal such as a zinc and/or aluminium alloy The core 29 of the first material provides an accurate profile for the required composite component. However the core does not need to be structurally strong as it defines a profile onto which the outer sheath of the second material, in the form of a metallic exoskeleton, is applied. The second material has relatively greater structural strength than the first material and provides a substantial proportion of the structural strength of the composite component.

Figures 3 to 5 show examples of inserts that can be utilised in a composite structural component in accordance with the present invention.

Figure 3 shows a threaded insert 23 with a location spigot 39. The threaded insert comprises an elongate cylindrical body comprising a self forming thread 33 on a first end 35, a region of serrated surface 37 and a substantially smooth region 38 of the body of the insert, all of which in use are inserted into the body of the core of the first material, and the location spigot 39 on a second end 41 that will protrude from the first material.

Figure 4 shows a threaded insert 25. The threaded insert comprises an elongate body comprising a self forming thread 33 on a first end 35, a region of serrated surface 37 and a substantially smooth region 38 of the body of the insert, all of which in use are inserted into the body of the core of the first material, and a threaded hole 43 on a second end 41 that will protrude from the first material.

Figure 5 shows a threaded stud insert 27. The threaded stud insert comprises an elongate body comprising a self forming thread 33 on a first end 35, a region of serrated surface 37 and a substantially smooth region 38 of the body of the insert, all of which in use are inserted into the body of the core of the first material, and a threaded stud 45 on a second end 41 that will protrude from the first material.

The core 29 of the first material can be produced, by methods known to a person skilled in the art, with accurately located apertures, for example location holes into which inserts can be provided during manufacture. The location holes may only extend into the core a limited depth, for example sufficient to receive the thread 33, and serrated and smooth regions 37, 38 of an insert such as threaded inserts 23, 25 or threaded stud insert 27. The location holes are provided such that the inserts are positioned at required positions in the final composite - 9 - structural component to correspond to the position of fixtures on a separate body.

Alternatively, a location hole may extend through the entire thickness of a portion of the core to receive a liner insert, for example, in the form of a hollow metal tube with an outer configuration substantially the same as the configuration as the location hole in the core and a length substantially the same as the thickness of the portion of the core, such that the inner surface of the location hole is lined along its entire length. The lined location hole through the final composite structural component can be used to secure the composite structural component to a surface by passing fixing means, for example bolts, through the lined location holes.

Figures 6 and 7 show a core 29 of the first material with a threaded insert 23 provided at the second longitudinal edge 7, a threaded insert 25 provided at the first longitudinal edge 5, and a threaded stud insert 27 provided at the apex 9, wherein the longitudinal axis of each of the inserts is aligned with the longitudinal direction of the elongate body. The core 29 of the first material is produced with apertures 47 in the region of the inserts such that the serrated surfaces 37 of the inserts are exposed when inserted into the location holes. The exposed serrated surfaces are used to form a bond with, and key to, the second material, as will be described hereinafter.

The method of manufacturing a composite structural component in accordance with the present invention will now be described.

Initially, using computer-aided design means known to a person skilled in the art, the required dimensions and profile of a component are determined and a computer model is produced for use in a process utilising stereolithography. By means of stereolithography a three dimensional core of the first material is produced using the computer model based on the computer-aided design to control laser curing of successive cross sections of a liquid resin, for example a photopolymer. Successive layers of resin are each exposed to ultraviolet laser radiation causing the resin to solidify and build up a core with the same dimensions and configuration of the computer design.

The computer design is such that any location holes that are required are formed as the core is built up. The location holes can be formed, for example, with circular, hexagonal or other cross sections depending on the configuration of the outer surface of the inserts that are to be installed. r - 11

On completion of the installation of the inserts, the second material is deposited on the core of the first material, and the inserts, by means of thermal spraying.

The thermal spraying process is, for example, a process for depositing metal onto a substrate. An energy source, for example an electric arc, combustion flame or plasma flame, is used to melt a metal, for example a zinc and/or aluminium alloy, in the form of a wire, powder or ingot. A gas, for example compressed air or nitrogen, is used to atomise the molten metal and propel it onto the core of the first material and the inserts. The successive deposition of the metal by the thermal spraying process produces a sheath, for example about 1.5mm to about 3.Omm thick, and preferably about 2.Omm thick, on the exposed surfaces of the core of the first material. The thickness of the metal sheath can be increased in areas of the composite component that require additional strength, or that will be machined in a secondary operation such that a proportion of the sheath can be removed without exposing the core material.

During the application of the second material, the action of the thermal spraying covers and fills the hereinbefore mentioned serrated surfaces 37 of the inserts that are exposed in the apertures 47 of the core 29. Therefore, the thermally sprayed second material bonds and keys the l - 12 inserts securely in position within the composite structural component as the serrated surfaces become embedded in the sheath of the second material as the sheath is formed.

The thermally sprayed second material can, for example, be applied by hand-spraying or by a robotic process.

Certain areas of the core and inserts may not require the application of the sheath of the second material, for example the mating faces of the inserts, and holes and studs associated with the inserts. These surfaces can be covered by masking material, for example sacrificial plugs, caps, tape and/or plates, prior to the application of the thermally sprayed second material. The thermally sprayed second material can then be applied to the inserts provided within the core and the sheath of second material will only be formed over the unmasked areas. After spraying, the masking materials are removed. Any excess sprayed material around the masked edging is removed, for example by finishing.

Where insert lined location holes are present through the entire thickness of a portion of the core, the location holes being used for the accurate locating and fixing of the final composite structural component, pins with the - 13 same configuration as the inner surface of the liner insert in the location hole are used to fill the hole prior to thermal spraying. In order that the pins can be located and removed after thermal spraying, the pins are of sufficient length to extend beyond the plane of the surfaces being sprayed with the second material. Following the spraying process each pin can be pushed out of the composite structural component leaving behind an insert lined location hole free from second material on its inner surface. The presence of the sheath of second material remaining over the opposite ends of the liner inserts secures the liner inserts within the composite structural component.

Additional surface finishing, for example polishing, painting, electrolytic plating or chemical plating, or secondary machining operations, can be carried out on the composite structural component as required for an intended application.

Long flat profiles on the composite structural component may require additional reinforcement to provide sufficient structural strength. This reinforcement may be supplied by means of using relatively large apertures in the profile, for example aperture 21 provided in the first side 19 of the embodiment shown in Figures 1, 2, 6 and 7, to enable - 14 additional second material to be applied to these areas of the profile. The presence of an aperture enables the sheath of the second material to be formed on both sides of the profile as well as on the exposed surface of the aperture, thus providing additional reinforcement.

The aperture 21 is formed with smooth radius profiles such that the potential for the formation of stress points within the sheath of second material is reduced.

Another method of providing long flat profiles of a component with additional structural strength which may be used where apertures through the component are not suitable, for example due to cosmetic or functional reasons, will be described with reference to Figures 8 and 9. In this case the core of the first material is produced with a recess 51 provided in a first side 53 of the core to such a depth that only a thin layer 55 of material remains between the deepest portion of the recess and the outer surface of a second side 57 of the core opposite the recess 51. The thin layer 55 is profiled at the perimeter 59 of the recess such that it can be subsequently separated by fracture from the remainder of the core.

As shown in Figures 8 and 9, the shape of the recess is such that an island 61 of core material remains connected - 15 to the thin layer 55. The island 61 and thin layer 55 within the recess 51 form a removable plug 55, 61. The second material, in the form of thermally sprayed metal, is then applied to the second side 57 producing a substantially flat surface free from the presence of apertures. On the first side 53, thermally sprayed second material is deposited up to the edges of the recess. Once the required thickness of second material is deposited on the first and second sides 53, 57, the plug 55, 61 of core material is removed from the recess by breaking the profiled edges and exposing the inside face of the sheath of second material that was deposited on the second side of the core. Thermally sprayed second material is then applied into the recess, bonding together the second material that has been previously deposited on both sides of the core.

In this way, additional reinforcement is provided by the second material on the additional surface area formed by the recess, whilst the second side is formed without the presence of apertures.

The recess produced in the core has rounded profiles and edges to reduce the potential for the formation of stress points within the sheath of second material. - 16

Although Figures 3 to 6 show specific embodiments of inserts which can be incorporated into a composite structural component in accordance with the present invention it should be appreciated that other inserts, for example bush liners, eccentric adjustable position location bushes, profiled inserts and mounting plates, may also be used. It should also be appreciated that a composite structural component in accordance with the present invention need not contain any inserts.

Where the composite structural component is to be utilised in support fixtures such as rapid welding fixtures, material handling grippers, assembly fixtures or location fixtures, the composite structural component may be used as a location support for a separate component. The positioning of the composite structural component relative to its surroundings may utilise, for example, shim adjustable and cam adjustable locating means as known to a person skilled in the art.

The composite structural component can also be utilised as an adjustable tooling support mounting for items, for

example clamps.

Due to fact that complex forms can be generated in the composite structural component by means of the direct - 17 production of the core based on computer-aided designs, a composite structural component in accordance with the present invention can be produced which possesses multiple mating faces or location sites.

The composite structural component may be used to produce working prototype components of cast parts. These prototype components of cast parts may, for example, include machining operations as would be carried out to a casting.

Complex structures, for example motorcycle frames which are conventionally constructed by fabricating castings and tubular components, could be produced as a single composite structural component in accordance with the present invention. Inserts for ancillary items, for example engine and suspension mountings, could be included. As mentioned hereinbefore, the sheath of second material can be applied with a relatively larger thickness where machining operations are required, for example for head-stock bearing mountings.

Fabricated steel structures, for example motorcycle seat support frames, can be replaced with composite structural components in accordance with the present invention. The composite structural component could provide, for example, - 18 the seat support, battery box and rear body profile as a single component.

Composite structural components in accordance with the present invention could also be used, for example, in furniture, architectural structures, general automotive components and structures, and medical (including prosthetic) components.

The method of producing the core of the first material has been described as being accomplished using the process of stereolithography. However, it should be understood that other methods for producing three-dimensional representations based on computer-aided design may be used.

One example of another method to produce the core of the first material is selective laser sintering which creates the three-dimensional core, layer by layer, by sintering successive layers of powder into a unified core by heating the powder using a carbon dioxide laser. Another example is a process wherein a method similar to ink jet printing is used but the print heads deposit successive layers of photopolymer, rather than ink, and the successive layers of photopolymer are cured using an ultraviolet lamp to form the three-dimensional core. l - 19

Depending on the form of the first material and/or the means of producing the core of the first material, the core may require some surface preparation, for example the application of a primer, or chemical etching, prior to the application of the second material to aid bonding between the first material and the second material.

The method of producing a composite structural component in accordance with the present invention as described herein enables a cost effective and relatively quick manufacture of a component directly from a design concept, which possesses sufficient structural strength for the intended application.

The manufacture of the composite structural component in accordance with the present invention enables sufficiently strong support fixtures to be produced which have relatively less mass than a substantially similar support fixture with similar strength that has been manufactured from a single material, for example plastics material or metal.

Claims

À. . -. : À À c e À CLAIMS

1. A composite structural component comprising a core of a first material and an outer sheath of a second material, wherein the second material has greater structural strength than the first material.

2. A component as claimed in claim 1, wherein the first and second materials are dissimilar.

3. A component as claimed in claim 1 or 2, wherein the first material comprises a sistered powder material.

4. A component as claimed in claim 1 or 2, wherein the first material comprises a plastics material.

5. A component as claimed in claim 4, wherein the plastics material is a cured photopolymer.

6. A component as claimed in any preceding claim, wherein the first material is a material manufactured by rapid prototyping means.

7. A component as claimed in claim 6, wherein the rapid prototyping means is stereolithography means.

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8. A component as claimed in claim 6, wherein the rapid prototyping means is selective laser sistering means.

9. A component as claimed in claim 6, wherein the rapid prototyping means is polyjet means.

10. A component as claimed in any preceding claim, wherein the second material is a metallic material.

11. A component as claimed in claim 10, wherein the metallic material is a thermally sprayable metallic material.

12. A component as claimed in claim 11, wherein the thermally sprayable metallic material is a zinc alloy.

13. A component as claimed in claim 11 or 12, wherein the thermally sprayable metallic material is an aluminium alloy.

14. A component as claimed in any preceding claim, wherein the composite structural component comprises at least one insert.

15. A component as claimed in claim 14, wherein the at least one insert is selected from bush liners, threaded . ec. À. ;. À:. e.e - 22 - inserts, threaded inserts with locating spigots, threaded stud inserts, eccentric adjustable position location bushes, profiled inserts and mounting plates.

16. A component as claimed in claim 14 or 15, wherein the at least one insert is positioned to enable accurate location of the composite structural component in relation to a fixing surface.

17. A component as claimed in claim 16, wherein the at least one insert is positioned for the attachment of the composite structural component to a surface.

18. A component as claimed in claim 16, wherein the at least one insert is positioned for the fixing of attachments to the composite structural component.

19. A component as claimed in any one of claims 14 to 18, wherein the at least one insert has means for being embedded into the sheath of the second material.

20. A component as claimed in claim 19, wherein the means for being embedded is a serrated surface.

21. A component as claimed in claim 20, wherein the serrated surface is keyed to the second material.

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22. A component as claimed in any preceding claim, wherein the sheath of the second material surrounds only a proportion of the first material.

23. A composite structural component substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

24. A method of manufacturing a composite structural component comprising the steps of providing a core of a first material and depositing a second material onto an outer surface of the first to form a sheath of the second material, wherein the second material has greater structural strength than the first material.

25. A method according to claim 24, wherein the first and second materials are dissimilar.

26. A method according to claim 24 or 25, wherein the first material comprises a sistered powder material.

27. A method according to claim 24 or 25, wherein the first material comprises a plastics material.

28. A method according to claim 27, wherein the plastics material is a cured photopolymer.

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29. A method according to any one of claims 24 to 28, wherein the first material is manufactured by rapid prototyping means.

30. A method according to claim 29, wherein the rapid prototyping means is stereolithography means.

31. A method according to claim 29, wherein the rapid prototyping means is selective laser sistering means.

32. A method according to claim 29, wherein the rapid prototyping means is polyget means.

33. A method according to any one of claims 24 to 32, wherein the second material is a metallic material.

34. A method according to claim 33, wherein the metallic material is a thermally sprayable metallic material.

35. A method according to claim 34, wherein the thermally sprayable metallic material is a zinc alloy.

6. A method according to claim 34 or 35, wherein the \rmally sprayable metallic material is an aluminium cee. ;e À:e at'. -

37. A method according to any one of claims 24 to 36, wherein the composite structural component comprises at least one insert.

38. A method according to claim 37, wherein the at least one insert is selected from bush liners, threaded inserts, threaded inserts with locating spigots, threaded stud inserts, eccentric adjustable position location bushes, profiled inserts and mounting plates.

39. A method according to claim 37 or 38, wherein the at least one insert is positioned to enable accurate location of the composite structural component in relation to a fixing surface.

40. A method according to claim 39, wherein the at least one insert is positioned for the attachment of the composite structural component to a surface.

41. A method according to claim 39, wherein the at least one insert is arranged for the fixing of attachments to the composite structural component.

42. A method according to any one of claims 37 to 41, wherein the at least one insert has means for being embedded into the sheath of the second material.

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43. A method according to claim 42, wherein the means for being embedded is a serrated surface.

44. A method according to claim 43, wherein the serrated surface is keyed to the second material.

45. A method according to any one of claims 24 to 44, wherein the sheath of the second material surrounds only a proportion of the first material.

46. A method of manufacturing a composite structural component according to any one of claims 24 to 45 and substantially as hereinbefore described with reference to the accompanying drawings.