The intelligent master model (IMM) of stamping process planning for automobile panels is composed of a knowl- edge base, process control structure (PCS), process planning optimization (PPO), process information model (PIM), and linkable environment (LE), which are inte- grated and combined based on KBE. The structure of the IMM is shown in Fig. 1. The IMM of process planning  is

Fig. 1  IMM of process  planning

With a process information model, the process planning can be completed through knowledge-reasoning and de- cision-making based on knowledge encapsulated in the objects.

The PCS is a key point to ensure process planning is integrated and consistent; it manages the process informa- tion model, process planning to generate stamping process plans and detail design, and controls the changes of the planning. In IMM, the PCS comes into being dynamically along with the process planning. If one part of PCS is created, it will monitor and control relevant planning and information subsequently. When results of process plan- ning are deleted, the corresponding PCS part will fade away accordingly.

The LE provides several methods to deal with the links among process planning procedures, the geometry between product and detail design of workpieces. To achieve intelligent process planning for large complicated stamp- ings, there are problems to solve, i.e. linking of process planning procedures, the geometry link between product and detail design of workpieces. The LE provides several methods to deal with these links, e.g. parameters variable link, data structures link, and geometrical link.

The PPO is a methodology of design optimum for complex engineering, which can deal with the complicated optimization problem of process planning in an economic view.

3.2 The framework of CAPP system based  KBE

The stamping CAPP system for automobile panels based on the intelligent master model above consists of several stages such as stamping features extraction from product data, operation features reasoning from stamping features to form a process information model, process planning to get the sequence of operations and relevant tools, detail design for workpieces, simulation for detail design, and finally the process plans and 3D die-face model generation which is shown in Fig. 2. It is a tangible activity level to control and frame a CAPP system for automobile panels.

Fig. 2  Overview of the process plan generation based on   IMM

In the CAPP system, stamping process planning of automobile panels needs to first establish a process information model based on a 3D model product and feature technology. Stamping features are extracted, and operation features are attained subsequently. The features all carry knowledge about themselves, the process and constraints. Then the PIM and PCS are established. There- after, the sequence planning is setup based on PIM and knowledge such as operation sequence rules, operation combination guides and reasoning methods, and then the dies and machinery are options.

Along with the process of the planning, PCS, PPO and LE of IMM are built by knowledge driving. PCS consists of an integrated collection of tasks that can initiate, control, manage, evaluate and update all the planning information and results timely. PPO optimizes process paths and enter- prises resource environments, and PCS and PPO carry out the optimization and find the optimal solution. PCS and LE make process planning associated and linkable.

accessing C programs from the KBE language described under External Function. For access to named attributes from C, there will be a utility program that takes a design definition in the language and produces C bindings to access the attributes of an object instance of that design. The access consists of functions and methods for getting and setting the value of the named attributes of object instances. Additionally, there are UDF and UDO in UG/ CAD and UG/KF, which can be dealt with by UG/Open and UG/KF. What is more, Unigraphics is integrated with many other knowledge tools and sources, such as spread sheets, other ICAD KBE language systems, finite element analysis, CAM, etc.