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A formalism for symbolic representation of threedimensional model and its use for knowledge representation and control structure are presented. A robust feature-based &sign (RFBD) approach has been developed to represent three dimensional objects and to provide meaningful geometric and topological properties for manufacturability evaluation. For knowledge acquisition, binary syntactic primitive pairs have been established for high level symbolic reasoning. Symbolic reasoning tables provide five stages for proper knowledge invocation. This hamework enables the system to reason about geomeeic shape based on syntactic pattern primitives and not on features. Both production rule systems and frames are used to represent the declarative and procedural knowledge sources in the EXCAST-1 .O (the expert system). Automatic meta-rule formation is proposed as a part of knowledge refinement process and the semantic data model is also proposed to aid various CAM applications for use in RFBD. The implementation of the algorithms and examples are provided.

Part descriptions of a 3-D computer-aided design model are in a form of basic geometry and topology to which manufacturing process and engineering analysis cannot be directly applied. A formalism for symbolic representation of a three-dimensional pattern model is presented to aid local and global shape analysis of casting design. Local shape analysis is carried out based on symbolic representation and global shape analysis is performed by analyzing the extracted skeleton from a discretized object.The purpose of local shape analysis is to reason about local shape characteristics so as to alter the design to obey casting requirement. On the other hand, the purpose of global shape analysis is to locate and measure global shape characteristics, thus allowing the system to aid the decision making process in evaluating the global casting soundness. The main aim of developing an expert system for casting design is to provide the casting designer with a tool for on-line manufacturability evaluation of a part design while the functional design is being performed. This paper explains the basic concepts of the three-dimensional pattern model and describes its use for castability evaluation of casting design. An implementation of the algorithms and examples are provided.