A CAD/CAPP interface for complex rotationally symmetric parts

Abstract

A new methodology for interfacing Computer-Aided Design (CAD) and Computer-Aided Process Planning (CAPP) based on automatic feature recognition is proposed in the domain of complex rotationally symmetric parts. The interface system consists of three stages: (1) Initial Graphics Exchange Specification (IGES) data translation, (2) polygonal decomposition or splitting, (3) automatic recognition of precedences and features. In the data translation stage, IGES data are transformed to multi-sectional chains of the upperhalf profile of a part and a raw stock. For the raw stock, not only a box shape but the non-rectangular one is also considered. In the polygonal decomposition stage, the removal volume is decomposed into a data structure of a Pseudo-polygon (Pgon). The Pgon data structure based on the surface classification (real, virtual, partial, and embedded) is suggested as a new feature representation scheme. In the automatic recognition stage, the geometric precedence relationship between Pgons is automatically recognized, and then structured globally into a precedence tree form. The feature class and instances are automatically identified from the decomposed Pgons.