Making the cut: tools for machining composites

Manufacturers of large structures often need to remove weight from the product, which has pushed the greater use of composite materials. Leading the way are aircraft structures, wind turbine blades, Formula One monocoque cabins and, increasingly, structures on cars. The Jaguar F-Type has carbon-fibre wind mirror covers, bonnet louvres and a variant has a carbon-fibre roof.

The growth of carbon-fibre applications  has driven new machining technologies for composites. Machining techniques, cutting tool designs and workholding solutions have been refined, but the biggest area is cutting tool design, with a growing  range of tooling companies introducing new designs to overcome the problems of machining composites, which behave very differently to metals. Layers, or plies, of fibre and resin bonded together react differently when placed under the force of a cutting tool.

“The biggest difference is in the chip formation mechanism, which you have no control of for composites, as the material shatters,” said Dr Kevin Kerrigan, composites machining technology lead at the Advanced Manufacturing Research Centre (AMRC)  with Boeing near Rotherham. Dust is the predominant feature when composite machining, as the cured epoxy resin layers disintegrate and throw up micro-sized particles.