A FORMAL APPROACH TO INTEGRATING COMPUTER-AIDED PROCESS PLANNING AND SHOP-FLOOR CONTROL

A formal approach for integrating Computer-Aided Design (CAD), Compute r-Aided Process Planning (CAPP), and shop floor control for rotational components is presented in this paper. It is assumed that this approa ch will be implemented within the framework of a three level hierarchi cal CIM architecture that consists of the following levels in the hier archy: shop floor, workstation and equipment (Joshi et al., 1991). Our approach to CAPP consists of machining feature identification, defini tion, classification, representation, and reasoning, provided through a CAD model of a product. Geometric entities are identified from a Dra wing Exchange Format (DXF) file. The identified entities form the basi s for the construction of primitive manufacturing features. The primit ive features are assembled together based upon the precedence among fe atures, into a graph, called a feature graph. However, the primitive f eatures may or may not be manufacturable in terms of depth of cut, too l geometry, surface finish, and material handling required. Hence it i s necessary to con vert the feature graph into a manufacturing task gr aph, which consists of specifications of alternative functional tasks that are manufacturable. The task graph may be converted into a hierar chical set of process plans, based on the planning criteria at each le vel in the control hierachy, to reflect the processing requirements at each level. The shop planning function decomposes the task graph into a set of workstation level plans. Each workstation level plan is aggr egated into a set of equipment level process plans by the workstation planning function. The equipment level plan is converted into a unique task sequence by the equipment planning function. This sequence is th en executed according to specifications by the equipment level executi on function. Provision of alternative routes in process plans provides for flexible means of on-line planning and control.