Integrated machining tool path planning using feature free spaces

We describe an automatic machining tool path generation method that integrates local and global tool path planning for machining features. From the solid model and the tolerance specifications of the part, we automatically recognize machining features, and obtain the geometry-based precedence relations between these features. A separate process planning module uses this information to determine the machining sequence, tool selections, and machining conditions. From the resulting process plan, we then generate machining tool paths for each set-up, combining local and global tool paths. Machining features are expanded through their fictitious faces to obtain feature free spaces. These comprise the cells of a free space decomposition, which enables the use of established robot motion planning techniques. Global tool paths between features are generated incrementally by searching the adjacency graph of feature free spaces, which represents the free space of the part at each step of the process plan. Local tool paths for each machining feature are generated by successive offsetting operations. The start and end positions for each feature's local tool paths are selected using a heuristic method to minimize the cost of each segment of the global tool path. This feature recognition method and the automatic tool path generation method are being developed as modules of a comprehensive machining process planning system.