Cutting & machining

Composites are generally manufactured close to the end shape required. Therefore, any post-manufacture machining is generally trimming or addition of design features such as holes and profiling for attachment. Cutting is generally recommended with some form of liquid cooling which helps to remove dust and prolong tool life. Dust from carbon fibres is abrasive and conductive. Therefore, it is advisable to prevent the dust entering the machinery or electrical components.

The more common method for milling uses a rotating tool or blade. The blades in saws or milling tools generally need to be coated to prevent premature wear when cutting tough composites containing carbon or aramid fibres. Diamond coated carbide tools provide a good tool for composites cutting, while polycrystalline cutting tools have a far superior cutting life, albeit at a higher cost. These tools are brittle and subject to easy damage from chipping and breakage.

For cutting of trim, particularly with non-straight edges, a water jet cutter provides a high accuracy high quality finish. The process cuts at low temperature reducing potential damage. An abrasive grit is used along with a high pressure water jet allowing cutting rates in excess of 150 mm/minute for laminates less that 13mm thick. The feed rate can be lowered to prevent the cut edge being curved through the thickness, particularly on thicker components.