Patent Application
20120181730
The present invention relates to a cutting tool, a method of drilling a hole in a dry fibre assembly, and a method of manufacturing a composite component.
To manufacture composite materials using infusion processes such as Resin Transfer Moulding®, it may be necessary to cut tight tolerance holes in the dry fibre lay-up prior to infusion to locate the lay-up to the cure or infusion tooling and/or keep the dry fibre assembly in place during the forming operation. A wide variety of different cutting methods can be considered for this purpose, such as Numerically Controlled (NC) ultrasonic ply cutting, water jet and laser cutting, conventional or NC-drilling, pressing or punching and orbital drilling. However, none of these techniques are suitable for cutting accurate holes in thick dry fibre assemblies.
Conventional drills are prone to snagging on the fibres, which can damage the material and increase the expected tolerance in the size of the resultant holes. Moreover water jet cutters can contaminate the lay-up, while laser cutters often burn off the binder from the cutting area. Consequently, these devices are rarely used.
The most common method is to cut the holes manually with a knife. Although this can provide satisfactory results with relatively thin assemblies of dry fibre, this technique is not sufficiently accurate for thicker dry fibre assemblies. Likewise, punching or pressing may prove suitable with thin dry fibre assemblies. However, with thicker dry fibre assemblies, the cutting tool becomes prone to failure.
Disposing of the waste produced during the cutting process can also be a significant problem. With conventional drilling techniques, the cutting tools can quickly become clogged with waste material, preventing long term continuous drilling and making the process inefficient.
A first aspect of the invention provides a cutting tool comprising: a rotatable hollow tube with an inlet at a distal end of the tube and a cutting edge at the perimeter of the inlet, the tube being arranged to rotate when in use so as to cut a work piece with the cutting edge; and an auger housed within the hollow tube, the auger being arranged to rotate when in use so as to feed cut material from the inlet along the hollow tube, wherein a distal end of the auger is set back from the cutting edge of the tube.
A further aspect of the invention provides a method of operating the tool of the first aspect of the invention, the method comprising rotating the hollow tube so as to cut a work piece with the cutting edge; and rotating the auger so as to feed cut material from the inlet along the hollow tube.
The hollow tube may further comprise an outlet for expelling the cut material. This outlet may be an axial hole at a proximal end of the tube, or more preferably an outlet hole in a side of the hollow tube. A vacuum pump may be coupled to the outlet so as to remove the cut material, optionally via a vacuum chamber which surrounds the hollow tube at an axial position aligned with the outlet hole.
The cutting edge may be circular or may comprise one or more teeth. Preferably the teeth have edges which deviate from a circular line transverse to the axis of the hollow tube by an angle no greater than 90°.
The hollow tube and the auger may be rotated in the same direction and at the same rate. In this case means may be provided (such as a set screw) for preventing relative rotation between the hollow tube and the auger. Alternatively the auger may be rotated at a higher rate and/or in a different direction to the hollow tube.
A further aspect of the invention provides a method of drilling a hole in a dry fibre assembly, the method comprising engaging the dry fibre assembly with a cutting tool comprising a hollow tube with an inlet at a distal end of the tube and a cutting edge at the perimeter of the inlet; and rotating the hollow tube so as to cut the dry fibre assembly with the cutting edge.
A further aspect of the invention provides a method of manufacturing a composite component comprising: engaging a fibre assembly with a cutting tool comprising a hollow tube with an inlet at a distal end of the tube and a cutting edge at the perimeter of the inlet; drilling a hole in the fibre assembly by rotating the hollow tube so as to cut the fibre assembly with the cutting edge; infusing the fibre assembly with a liquid matrix after the hole has been drilled; and curing the liquid matrix.
The cutting tool may comprise a tool according to the first aspect of the invention, or a more basic cutting tool with no auger.
Preferably the cutting tool comprises one or more teeth, and the teeth have edges which deviate from a circular line transverse to the axis of the hollow tube by an angle no greater than 90°.
A further aspect of the invention provides a cutting tool comprising: a rotatable hollow tube with an inlet at a distal end of the tube, a cutting edge at the perimeter of the inlet, the tube being arranged to rotate when in use so as to cut a work piece with the cutting edge, and an outlet for expelling the cut material; and a vacuum pump coupled to the outlet of the rotatable hollow tube.
A further aspect of the invention provides a method of operating the tool of the preceding aspect of the invention, the method comprising rotating the hollow tube so as to cut a work piece with the cutting edge; and operating the vacuum pump to remove the cut material from the outlet.
Embodiments of the invention will now be described with reference to the accompanying drawings, in which:
The body of the cutting tool 4 is preferably formed from steel. The cutting edge 4 may be made from a hardened material such as tungsten carbide or diamond. Alternatively, the cutting edge 4 may be made from steel with a brazed-on hardened tip (for instance tungsten carbide).
A drill bush 11 is fitted into a pressure pad 12 and placed on the dry fibre assembly at a desired position as shown in
Cut material enters the inlet 2 and is ejected from the outlet 3, guided by an angled wall 5 shown in
After the hole 13 has been cut, the dry fibre assembly 10 is infused with a liquid epoxy resin matrix. The infused dry fibre assembly is then heated to cure the epoxy resin. A locating member (not shown) is inserted into the hole 13 during the infusion process to keep the dry fibre assembly in place.
The tooth shape shown in
The bottom of the tube 31 is hollow with an inlet 34 at its distal end and a cutting edge 35 at the perimeter of the inlet. The cutting edge 35 shown in
The auger 32 has a helical channel running from a sharp tip 37 at the distal end of the auger to an end 38 shown most clearly in
The vacuum connector 33 has a pair of sealed bearings 42, 43 which carry the tube 31 and enable the tube 31 and auger 32 to be rotated together whilst the vacuum connector 33 remains stationary.
The tube 31 has an outlet hole 44 in its side, shown most clearly in
The tube 31 is gripped by a drill (not shown) which rotates the tube 31 and auger 32 together. The auger 32 feeds cut material from the inlet 34 along the hollow tube, out of the outlet hole 44 and into the vacuum chamber 45. The cut material is then sucked from the vacuum chamber through the vacuum outlet 46.
In an alternative embodiment (not shown) the auger may be rotated at a higher rate and/or in a different direction to the hollow tube. In this case the set screw 41 will be omitted. If the auger is rotated in a different direction to the hollow tube then the direction of the auger thread will be reversed so that the cut material is fed in the correct direction. A gear box (not shown) can be used to generate the desired rate and direction for the two components.
In an alternative embodiment (not shown) the auger 32 may be omitted, along with the hole 40 in the tube 31. In this case the cut material is fed from the inlet 34 of the hollow tube to the vacuum outlet 46 by the action of the vacuum only.
When bound dry fibre is drilled, the cut material expands in volume. This leads to the production of a large quantity of waste cut material. By employing an auger and/or a vacuum pump, this large quantity of waste material can be disposed of quickly and efficiently allowing the tool to be used continuously for long periods of time.
The tip 37 at the distal end of the auger 32 is set back from the cutting edge 35,36 of the tube. This prevents the auger from snagging and/or tearing the carbon fibres as they are cut.
Hole tolerances lower than +/−0.1 mm in diameter have been achieved in dry fibre lay-ups using the tools described in
To improve the tool further, the tools 10, 30 may be fitted with an ultrasonic head (not shown). Vibrations produced by the ultrasonic head assist in the cutting process, allowing the operator to exert less force to manufacture the required holes.
Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0807639.0 | Apr 2008 | GB | national |
The present application is a divisional of U.S. application Ser. No. 12/415,202, filed Mar. 31, 2009 and is based on, and claims priority from, British Application Number 0807639.0, filed Apr. 28, 2008, the disclosure of which is hereby incorporated by reference herein in its entirety
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12415202 | Mar 2009 | US |
| Child | 13426130 | US |
