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

We describe a system that generates 5-axis roughing tool paths directly from a tessellated representation of a body. Instead of decomposing the shape into manufacturing primitives, we generate tool paths directly from the shape of the workpiece using measures of accessibility avoid collisions. There are three stages in our approach: visibility computation, posture definition and path interpolation. In the first stage, we use the concept of Visibility 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-holder or the spindle. In the posture definition stage, a local search is performed in the neighborhood of the visibility direction using rapid collision avoidance. The output of this step is a set of valid tool postures for every 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 we interpolate collision free tool paths by performing NC simulation and path correction within the loop of path generation using rapid collision detection algorithms. (C) 2000 Elsevier Science Ltd. All rights reserved.