4。5 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 work-pieces to suitable positions of the project, and decompose the process planning task into subtasks。 In IMM and process planning, according to the knowledge expression and decision-making 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 complicated 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 control the links and transfer the geometry information between different parts of the process planning。 In IMM, the parts of PCS come into being dynamically along with proceeding of the process planning。 If one part of PCS is created, it will monitor and control relevant planning and information subsequently。 When some results of process planning are deleted, the corresponding PCS part will fade away。

5 Conclusions

As the automobile body panel is one kind of sheet metal part with groups of free form surfaces and large size, the process planning is more complicated than common sheet metal stamping。 Yet the automobile panels can be considered as a combination of some common stamping, such as irregular drawing, flanging/bending, trimming, and piercing, etc。 However, because of over-complexity, stamping CAPP system for automobile panels is more difficult to implode effectively and practically。 It should deal with all knowledge from geometry, non-geometry, engineers’ experience, rules and criterions and successful cases of planning process-paths for automobile panels。 The process plans should instruct or guide how to  perform a complex procedure。 Based on KBE, new frameworks have been presented as an intelligent master model in the system level and as a procedure model in the activity level。 This master model brings forward a new concept and notion that knowledge, and thus KBE, is the kernel object of technology for specific domains in the manufacturing industry。 In accordance with these frameworks, an intelligent CAPP system has been specifically developed。 Based on feature technology, features have been extracted and represented by the object-oriented method。 Stamping features and their parameters have been defined and extracted based on feature technology and stamping process rules。 The whole product knowledge has been represented by frames which directly map to objects (or features) in the object-oriented sense。 Relevant appropriate operations features have been assigned to stamping features of products based on feature- operation criteria, and parameters of stamping features and their correlativity。 This assignment is a decision-making activity using a set of rules with a decision-making tree and model-based reasoning methods。 With knowledge between operations, such as operations order constraint (do-after) and operations combination constraint, the process path has been improved based on relevant intelligent reasoning methods。 Based on the relation (preferred-to) between processes and machines/dies, the structure of the die and machine for each process can be performed, while the process route has been determined。 In this stamping process planning, the procedure and information have been con- trolled by the process control structure to be associative and integrated。 This study can be used as the basis for future studies to enhance the complicated system。 Indisputably, much effort will be required in advancing the establishment of the practicality process planning function blocks and their mutual interaction。 Moreover, the conversion of these architectures into a prototype CAPP system will be a considerable endeavor。摘要汽车车身覆盖件是一种由各种自由曲面组成的金属薄板，其过程归化比普通薄板更有效和实际冲压更复杂。基于知识工程，新的框架已经出现，作为在系统级和程序模式的活动水平上的智能主模型。根据上述框架，一个智能CAPP系统已经被专门开发。基于特征技术，功能已通过面向对象的方法被提取。基于特征的技术和冲压工业规则，冲压功能和参数已经确定和提取。整个产品的信息直接映射到物体（或功能）的面向对象。基于特征的操作标准，冲压特征的参数及相关性，这项任务是一个决策活动，使用一套与规则决策树和基于模型的推理方法。不同操作中间，如操作顺序约束和不同操作组合约束，进程路径得到改善，根据有关智能推理方法。基于关系（首选地）之间工艺和设备模具，可以确定每道工序机和模具的结构，因为工艺路线已经确定。在这种冲压工艺规划中，程序和信息的关联集成一个进程控制结构。