Finding feasible tool-approach directions for sculptured surface manufacture

Abstract

Determining tool-approach directions is an important issue when an effort is made to transfer CAD data into manufacturing automatically. An algorithm is developed to determine whether a given part can be machined on a three-axis milling machine. In the algorithm, a sculptured surface is first approximated with smaller subpatches by an adaptive subdivision method. For the unit normal vector to each subpatch, a hemisphere is then defined. Any point on the hemisphere defines a feasible tool-approach direction for the corresponding subpatch. The intersection of the hemispheres for the sculptured surface is a polyhedron. A set of points on the polyhedron is the set of feasible tool-approach directions for the sculptured surface. If a set of feasible tool-approach directions exists for a sculptured surface, the NC tool paths and G-codes for machining the surface on a three-axis milling machine can be generated automatically by an NC tool-path generation algorithm. The algorithm can be used for orientation and fixturing of the workpiece for interference free machining. The algorithm for finding feasible tool-approach directions is implemented in C running on a Sun engineering workstation as a module in an integrated sculptured surface design and manufacturing (ISSDM) system.