【正文】 ed 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. Thereafter, the sequence planning is setup based on PIM and knowledge such as operation sequence rules, operation bination 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 enterprises resource environments, and PCS and PPO carry out the optimization and find the optimal solution. PCS and LE make process planning associated and linkable. 4 Key points of process path generation Unigraphics has several features that provide a subset of the capabilities of a KBE language —UG/KFL, which provides a way to specify knowledge rules that can cover all Unigraphics applications. The stamping CAPP system for automobile panels has been developed based on the frameworks advanced above, which choose C and UG/KF language as t he implementation language, a nd ACCESS as its database o n t he UG/CA D development environment. UG/Open and UG/Open++ allow custom i zation and extension of Unigraphics using a standard procedural language (C and C++). UG/KFL provides a way to specify knowledge rules that can cover all Unigraphics applications. Rules of UG/KFL are easily written by the developer, easy to read, understandable, and reusable by the user. Furthermore, UG/Open can be integrated with KBE by 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. Stamping feature To generate appropriate process plans, the product data requires the original inputs, which includes the geometry, topology, tolerance, material and quantity of product. Based on the feature technology and stamping technology, a stamping feature is the portion of a part which can be formed by means of certain stamping operations. For ex ample, a drawn feature or bend feature is defined as the main feature, which is to describe the near shape of a ponent, while flange, hole, emboss, bead, notch and flangehole are defined as the auxiliary ones, which are required to describe the local part of the final shape. Using feature technology and the geometry extraction method, the stamping design features, such as the main forming feature (. drawing, bend), flange, hole, emboss, bead, notch, and so on, can be extracted from a 3D solid model, which are first defined as UG/UDO. For example, Fig. 3 shows the stamping features of one automobile panel. The stamping feature model should then be defined to represent product knowledge integrated and unambiguous. The stamping feature is represented as objectoriented class or object and instance using UG/KF language (UG/KFL)。amp。 therefore, the best process route should be selected according to the batch of production, design and manufacturing of stamping dies, cost, etc. while tool options, the equipment and dies for each process should be assigned to meet design specifications, and to achieve minimum machining time and maximum efficiency. Finally, the optimization of process planning [20] is realized for multiple purposes (best quality, maximizing efficiency, minimizing cost and time) by PPO based on KBE. PCS in process path generation Since the process planning is a dynamic course with several plans and design stages, PCS is a key point to ensure process planning is integrated and consistent. PCS man ages the process information model, assists in generating stamping process plans and detail design, and controls the changes during planning. There are several control variables for PCS including state variables for process planning, control variables for IMM, and state variables for stamping features, etc. The process control structure is shown in Fig. 10. In this CAPP system, the process planning is defined as a project. The project control can create a project, insert the part or workpieces to suitable positions of the project, and depose the process planning task into subtasks. In IMM and process planning, according to the knowledge expression and decisionmaking rules, the planning process control can set up the process information model based on features and their state variable, monitor planning process, feed the planning information and changes back to IMM, and control information transfer. The process planning is a dynamic process of information flow and transfer. The information link control ensures process planning information is associative and consistent. The added, extended, and modified information and its effects on the planning can be fed back to PIM and IMM so that the information of process planning can be updated timely and shared by different parts of the system. For the plicated and mass geometry information involved during the process planning, the links between features and product geometric information have been dealt with. The geometry link control can monitor and co