An intelligent object-oriented feature-based system for CAD/CAM integration

Abstract

(Uncorrected OCR) ABSTRACT This thesis describes the development of an intelligent feature-based design system EXPO (EXpert Process planning Object-oriented system) for integrating the CAD and CAPP functions in the design and manufacturing of prismatic machined parts. This research was organized into two phases. The first phase was to develop an interactive design environment for part specification in terms of volumetric machining features, while the second phase involved the establishment of a process planning system to convert the feature information to the corresponding machining processes and generate the NC part program. EXPO has been implemented by integrating an expert system development tool CLIPS (C Language Integrated Production System) with the solid modeller AME (Advanced Modelling Extension) of AutoCAD. The integration provides a foundation platform for knowledge processing. EXPO has employed a hybrid approach for knowledge representation by combining rule-based and object-oriented approaches. Thus, the knowledge based system can transparently access the geometric information and dynamically infer the knowledge from the geometric database for automatic reasoning. In EXPO, geometric reasoning has been successfully incorporated into the feature-based design system to detect and resolve feature interactions. EXPO takes the volume and surface information from the solid modeller and uses geometric reasoning to evaluate the feature interactions. Feature interactions may change the feature types and forms as well as the process sequence for producing the part. Feature-based design systems which cannot detect and resolve feature interactions are too restrictive for practical uses because the downstream applications are totally relied on the accuracy of the feature information. Thus, the systematic evaluation of feature interactions is one of the most ii essential feature-based functions. It constitutes the basis for validating the machining features in each design step, and is the key to guarantee that a part will be produced as it is designed in the design-for-manufacture environment. iii