Developing Research Of Object-Driving CAPP Expert System

CAPP (Computer aided Process Planning) is the critical technique for integration of CAD and CAM and CAPP expert system is the developing trend of CAPP. However, CAPP expert system currently cannot meet all the requirement of production practice, because of the uncertainty, complexity and experience dependence, as well as the problems in the availability, computer expression and process of process knowledge. Although there are many solutions for CAPP system developed based on 0-0 method, most of these systems is only made simpler by 0-0 method. In this paper, 0-0 method is used to present an unique solution of CAPP expert system in which, based on part objects and feature objects, process knowledge is extracted as various rule objects corresponding to different features that included in different feature objects as their attributes. So in reasoning, part objects and feature objects can directly drive the reasoning program working for specified rule sets to improve the reasoning efficiency. That's so called 'object driving' idea.In this paper, the concepts, structure and characteristics of expert systems are summarized, which provides for employing expert system model as the hierarchy of CAPP system.Description and input of the part information are the keys of a CAPP system. The modeling based on features is the best approach to the problem. In the paper, existing feature definitions and classes are summarized, and the hierarchy of the part information model is defined, the mapping concept of features to process methods and the object-driving process decision reasoning method are presented.0-0 method is used in part and feature modeling, class hierarchy is analyzed and built, designs of part class and feature class are completed, which provides for the object-driving reasoning.Process knowledge library model based on relation database is presented, which implements the separation between the process knowledge and reasoning program.Based on above work, an original system is developed which realizes basic functions of an object-driving CAPP expert system.