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Paul Crosby founded Crosby Composites (Brackley, Northamptonshire, U.K.) 25 years ago when the use of composites in Formula 1 (F1) racing cars was just beginning. “It was obvious that these materials were an opportunity that would get bigger,” he remembers, “so I started my own company.”
He introduced digital modeling and CNC machining eight years ago, with the help of software supplier Delcam Plc (Birmingham, U.K.), despite his reservations about cost. Starting with PowerSHAPE for basic part and tool design, Crosby’s designers found it easy to learn how to do complex modeling operations. PowerMILL — software that converts CAD models to NC toolpaths for multiaxis milling — was adopted on a 30-day trial, and Crosby never looked back.
Crosby says the software has helped produce F1 composite parts to levels of accuracy rarely seen in the industry. Part tolerances between ±0.1 and ±0.25 mm (±0.004 and ±0.010 inch) are a key differentiator for his business. Now, a third Delcam software suite is helping ensure part accuracy. PowerINSPECT On-Machine Verification software enables rapid inspection of complex parts or tools by comparing them with the CAD model, and it is compatible with a variety of coordinate measurement machines.
Crosby explains that machined holes and pockets in carbon fiber composites tend to be undersized because the material relaxes slightly when cut, which is difficult to predict because not all of the fibers are cut in the same orientation. To overcome this problem, the initial machining operation is followed by inspection on the machine tool with PowerINSPECT, which shows if material needs to be removed while the required extra toolpaths are easily generated in PowerMILL. In addition to increased accuracy, all machining and inspection can be completed on the machine tool on a single fixture, eliminating the need to move the parts between fixtures, which can affect tolerances.
The first set of 17 parts produced with this method was fitted onto a F1 race car with no misfits or rework, reportedly the first time for such an outcome in that FI team’s history.