Generating 5-axis NC roughing paths directly from a tessellated representation

We describe a system that generates 5-axis roughing tool paths directly fro m a tessellated representation of a body. Instead of decomposing the shape into manufacturing primitives, we generate tool paths directly from the sha pe of the workpiece using measures of accessibility avoid collisions. There are three stages in our approach: visibility computation, posture definiti on and path interpolation. In the first stage, we use the concept of Visibi lity to determine the directions from which a point in the delta-volume is likely to be accessible to an observer located outside the convex envelope of the object and describe a technique to compute this information rapidly using graphics hardware. However, visibility does not ensure accessibility because visibility cannot account for the diameter of the tool, the tool-ho lder or the spindle. In the posture definition stage, a local search is per formed in the neighborhood of the visibility direction using rapid collisio n avoidance. The output of this step is a set of valid tool postures for ev ery sample point in the delta-volume. Finally, all that remains to be done is to connect the valid postures into a valid continuous tool path. This is not a trivial task because the tool must not interfere with the part while interpolating between valid postures. In the third stage of our approach w e interpolate collision free tool paths by performing NC simulation and pat h correction within the loop of path generation using rapid collision detec tion algorithms. (C) 2000 Elsevier Science Ltd. All rights reserved.