Cutter accessibility analysis of a part with geometric uncertainties

In designing a holder part of a large stamping die, designers must consider not only the functional property of the part, but also its manufacturability. The holder part is usually produced by cutting and engraving table, wall, slot and pocket features into a raw cast object. The raw cast object has inevitable large shape errors. It generally has 5 to 10 mm shape difference from the nominal CAD model. This shape uncertainty causes various manufacturability problems in the milling process. The most serious problem is unexpected collisions between a cutter and raw cast object. They cause possible tool breakages and become obstructions to the cutter access to some regions on features. Since such features are not properly machined, costly re-designing the holder part is necessary. In this paper, the authors propose a manufacturability analysis system which can detect such un-machinable features caused by the shape uncertainty of the raw cast object. Proposed system computes a geometric model of a holder part with the maximum shape error by modifying the CAD model. Inverted offsetting and cutting simulations are successively applied to the model to extract the un-machinable region on the features. A system is implemented and some computational experiments are performed.