ROUGH CUT TOOL PATH PLANNING FOR B-SPLINE SURFACES USING CONVEX-HULL BOXES

The objective of this paper is to present a non-uniform layered rough cut plan for B-spline surfaces using convex hull boxes. The tool path plan generated by this method will rapidly remove most redundant mater ial from stock material without overcutting. First, a B-spline surface is decomposed into piecewise Bezier surfaces, of which the convex hul l boxes form an approximate model for rough cutting. Then, according t o the top planes of those convex hull boxes, the stock material is div ided into layers of different thickness. The cavity contour for each l ayer is obtained using a simplified union Boolean operation on convex hull boxes. Finally, from the top down, each layer is processed like a 2D pocket die cavity. The algorithm is implemented on a personal comp uter. It is shown that the rough cut plan is very efficient since no c omputation for solving nonlinear equations is needed, and no overcutti ng occurs since B-spline surfaces are protected by the convex hull pro perty of Bezier surfaces.