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Abstract
The precondition for process planning and process sequencing is existence of a valid feature precedence network. However, for complex designs with large number of features and relations between them, such network may be very complicated and very difficult to evaluate manually. This paper proposes Petri nets as a tool for modeling of feature interactions. The architecture of the prototype system is presented and the algorithm for creation of the Petri net that corresponds to the feature precedence network is described. The necessary transitions and places (based on feature model) for constraints between machining processes are identified. The feature precedence network is evaluated with the help of Petri net simulation. An implementation of the prototype system that generates and simulates Petri net for given model of manufacturing features and their relationships is described and its performance is shown on several examples.
Keywords
CAPP, manufacturing features, feature precedence network, petrinets
1. Introduction
Today's global economy with its accompanying international competition presents a challenge to the manufacturing industry. The need to develop, manufacture and market a well-designed product at a competitive price in a short time is emphasized more than ever. In order to survive in this increased level of competition, manufacturing systems should be designed to be more product-oriented having lower lead times, minimal work-in-progress, just-in-time flow of material, high efficiency and flexibility of manufacturing capacity utilization [11]. This calls for a streamlined integration of all processes leading from product concept design to its realization as a marketable product. As significant cost decisions are made during the design stage of a product, an efficient approach towards the integration of computer-aided design (CAD) and computer-aided process planning (CAPP) systems is required.
The increased use of computers has produced great advancements in design, process planning and automated manufacturing activities. Product design systems have improved with the development of CAD systems that allow a designer to use parametric solids, profiles and design features to generate the product. Process planning systems, both generative and variant, have considerably progressed toward capabilities to generate alternate process plans incrementally. However, there has been not significant achievement in the efforts towards the complete integration of CAD and CAPP systems. Typically, the designer develops a solid model of the product according to functional needs,...