Rapid Calculation of Contact Points in Multipoint Forming CAD

A rapid algorithm for calculating contact points between punches and work-piece in multi-point forming CAD is proposed in this paper. The basic idea in the algorithm is to transform NURBS surface that describes the shape of a work-piece to multi-piece rational Bézier surface before the contact points are calculated. As a result,, the calculation can be made at relatively high speed since lots of recurrence from NURBS formula may be avoided. The algorithm has been verified by lots of practical examples, and the result shows that it can substantially improve calculation speed while keeping high precision and fully meet the need of engineering applications.