Assembly process sequence planning for STEP based mechanical products: An integrated model and system implementation

This paper proposes an approach to assembly planning for STEP (Standard for the Exchange of Product Model Data, officially ISO 10303) based mechanical products and systems, including STEP-based product assembly model, the representation, planning and optimization of mechanical assembly sequences. In this paper, a generic product assembly model is organized according to STEP, using mostly the entities of integrated resources and partly self-defined entities that are necessary for assembly planning. Based on this model, all feasible assembly sequences can be generated by reasoning and decomposing the leveled feasible subassemblies, and modeling them with Petri net. In order to obtain a good assembly sequence, a fuzzy assembly sequence evaluation index as a fuzzy number between 0 and 1, which is an aggregate measure of operation difficulty for the entire sequence, is proposed to evaluate, select and optimize the optimal assembly sequence. A prototype system is developed based on the proposed model for assembly planning. Finally, an industrial product exemplifies the proposed approach.