A hybrid feature sequencing approach to process planning for prismatic parts

One of the most difficult tasks in automated process planning is the determination of feature sequencing. Two major issues in this research are how to sequence features according to different priorities and how to recognize the optimality of developed sequences. This paper describes an approach both in mathematical modeling and applicable algorithm. A hybrid approach is used for identifying the needed operations sequence of machining prismatic parts on a three-axis milling machining center. In the proposed methodology, the feature sequencing is carried out in two levels: setup planning and tool planning. Various constraints on the precedence relationships between features are identified and heuristics (symbolic reasoning) and algorithms (computational methods) are created. Based on the precedence relationships between features, a sequencing method is developed to find the optimal plan(s) with a minimum number of setups in which the conflict between the feature precedence relationships and setup sequence is avoided. For each setup, an optimal feature machining sequence with minimum number of tool changes is also determined using a developed four-list algorithm. The four-list algorithm adopts two strategies in implementation. An example is provided to demonstrate this approach.