Prototyping a feature based modelling system for automated process planning

Abstract

In recent years, there have been tremendous amount of interest in manufacturing automation and Computer-integrated Manufacturing (CIM). To attain a high level of automation in CIM, there has been relentless effort in trying to integrate the islands of automation in manufacturing. These are often fraught with much frustrations and difficulties. The main clamity in integration is due to the mismatch of information available from the CAD system and that required by CAPP system. The geometric information generated by the solid modellers in most CAD systems are low level whilst the CAPPs will operate efficiently only at a higher level of abstraction. CAPP systems thrives on feature information but such information in CAD databases are rather implicit and at times not even available. Although there has been much research and development work in making these feature information in CAD databases more explicit through feature recognition and extraction, this is really a regressive step. A much better approach is to define features as they exist right at the start at the modelling stage and store these feature definitions in a feature database which can be assessed directly by CAPP. In this way the likelihood of making errors in interpretation is minimized as the feature information are derived at source.

This paper describes the prototyping of a feature-based modelling system in an AI logic language, Prolog. Feature hierarchy depicting the part-feature relationships can be defined by the designer when he is making the design of the part. By defining features as objects and through object oriented programming, generic and specialized feature properties can be defined or inherited through a child/parent relationship. These constituent features are composed semantically and meaningfully through a bottom-up strategy based on feature composition rules and feature primitives. The result of the parsing exercise is a solid representation of the global model depicted as a CSG tree of features. This solid model will ultimately be translated into solid modeller specific commands and further evaluated to give active boundaries representing geometric and topological information for rendering.