calculating, path-planning and some sketch map of work- pieces for specific types of sheet metal, such as axisym- metric and non-axisymmetric deep drawings, complex bendings and shearings, and so on.

The automobile body panel is one kind of sheet metal part, which is complicated in shape, with groups of free form surfaces, a large figure in size and is always man- ufactured by stamping processes. Automobile panels can be considered as a combination of some common stamping, such as irregular drawing, flanging/bending, trimming and piercing, etc. The process planning of these panels is more complicated than common sheet metal stamping, which is generally dependent on engineers experience to complete. It is believed that the process path plan for automobile panels is requisite and acquirable.

In essence, the stamping process path for automobile panels is to determine the necessary forming processes and their sequences in order to produce a particular part eco- nomically and competitively. Process paths generation is a decision-making process. Decisions on stamping opera- tions for a particular feature have to be formed on various independent conditions such as which operation should be performed with which die and tools and under what forming parameters. A CAPP system for these should be an integrated environment to deal with knowledge to reduce the dependence on engineers or experts, and realize the process planning with scientism. Thus, knowledge based engineering (KBE) is applied to advance the stamping CAPP system for automobile panels, and even to improve the competitiveness for the automobile industry. This paper is particularly concerned with the construction involved with developing a CAPP system based on KBE.

2 KBE in CAPP system for stamping

2.1 KBE

Knowledge based engineering (KBE) is one innovative method of artificial intelligence for engineering design developed in the 1980s. So far, there is no generally accepted and mature definition for KBE. However, it is recognized that KBE is an intelligent method to resolve engineering problems, which can realize inheritance, inte- gration, innovation and management of domain expert knowledge through the drive, multiplication and applica- tion of knowledge. A knowledge-based system (KBS) is one that captures the expertise of inpiduals within a particular field (the “domain”), and incorporates it and makes it available within a computerized application [15]. The level of complexity of the tasks performed by such a system can vary greatly. However, it can generally be said that while a domain expert would find them routine, they would be outside the capabilities of a person unfamiliar with the domain [16].

KBE provides an open architecture and reuse ability of experience and knowledge, which can deal with multi- domain and multi-expression of knowledge, and can form an integrated environment. A KBE application is   further

specialized, and typically has the following components of geometry, configuration, and engineering knowledge:

– Geometry – there is very often a substantial element of computer-aided design (CAD). Most of the software used to create KBE applications either has CAD capabilities built in, or is able to integrate closely with a CAD package.

– Configuration – this refers to the matching of valid combinations of components.

– Engineering knowledge – this enables manufacturing and other considerations to be built into the product design.

When a candidate application area requires a high degree of integration of the above elements, KBE is likely to be the best method for its integration. KBE is sometimes termed rule-based engineering, as within the discipline, knowledge is often represented by rules. These may be mathematical formulae or conditional statements, and although simple in concept, they may then be combined to form complex and powerful expressions. KBE systems, on the other hand, are usually provided with specialized geometrical capabilities, with the ability to embed engineering knowledge within a product model.