A DATA REPRESENTATION SCHEME FOR SHEETMETAL PARTS - EXPRESSING MANUFACTURING FEATURES AND TOLERANCE REQUIREMENTS

Development of an invaluable CAD/CAM system, from a pragmatic perspect ive, depends on the careful design of its data representation scheme t o cover the specific domain and ultimately increase productivity with good information support. Designers and manufacturers in the sheetmeta l industry have a particularly strong need for finding data representa tion schemes that can increase the efficiency and effectiveness of she etmetal production. Previous research in the area can hardly be applie d because shapes and processes of sheetmetal parts are quite different from the most-studied metalcutting parts. In this paper, a unique pro cess-driven, feature-hierarchical data representation scheme is propos ed. We develop a scheme for sheetmetal parts so that a designer can us e the process-related feature hierarchy to describe them and at the sa me time express design intention and tolerances. Features can be class ified into two types. One is called the master feature, which is used to represent the primary profiles of sheetmetal parts. The other type is called the manufacturing feature, which represents a single sheetme tal manufacturing process. Primitive features are defined to represent the manufacturing features. Compound features can be defined by combi ning primitive features to fulfill a specific design intention. To pre sent a sheetmetal part design that is ready for processing, assembly, and inspection, the geometric and dimensional tolerance information is added to the feature definition. The data structure for the scheme is developed considering the topology, geometry, and tolerance data. Fin ally, a prototype system called SMCAD is implemented using the solid m odeler ACIS to demonstrate the proposed sheetmetal design scheme.