Abstract
Abstract
This article is concerned with part representation and reasoning algorithms for automatic process planning in CADCAM (computer aided design and manufacture). Process planning involves the translation of a part description into instructions for a sequence of operations for the manufacture of the part. Part representations in CADCAM are reviewed, and a hierarchical representation is introduced which describes parts as the set-theoretic union of positive (protrusion) features, with the set-theoretic union of negative (depression) features subtracted. The model information hierarchy also incorporates topological relationships among features (adjacency, ownership and intersection), tolerances and links to a boundary representation (B-rep) geometric model. The hierarchical part representation is used as the basis for a reasoning scheme that uses topological relationships between features to restrict the search space of operation sequences. A recursive algorithm produces candidate operation sequences that are then ranked by applying manufacturing heuristics in a process called machining regularization. The representation approach is illustrated by an example, and possible extensions to the scheme are briefly discussed.