Using a feature-based model for automatic determination of assembly handling codes

Abstract

Automated concurrent engineering requires, among other things, that the assemblability of parts be evaluated during the design process. This evaluation can be made by determining an assembly part code from a solid model of the components. This research attempts to automatically derive an assembly handling part code from a solid model boundary representation. A rule based recognition system called AHPC (Automatic Handling Part Coder) was developed to extract the pertinent assembly features and then to convert these feature attributes to code digits. The UMass coding scheme is used in which the digits represent the overall shape, symmetry, and other assembly characteristics. Several previously uninvestigated features such as axial and transverse symmetries and other patterns of high-level features have been investigated and recognized, in addition to features such as holes, protrusions, slots, and steps. A technique called Feature Point Attribute Symmetry (FPAS) has been developed which converts a part to a feature-point model. Symmetry evaluation can be performed then by using this concise model and merely testing the symmetry of the feature points and the overall body shape. The system is implemented in Prolog on the Vax/Unix operating system. The test parts were created using the Romulus solid modeler. This system has been successfully implemented to generate assembly handling part code digits for a limited domain of parts.