Planning for STEP-based electro-mechanical assemblies: an integrated approach

Abstract

Assembly planning is a critical link between design and manufacturing stages. It is particularly critical for production automation and manufacturing integration due to the combinatorial complexity and the requirements of both flexibility and productivity. This paper presents an integrated approach and framework for planning STEP-based electro-mechanical assemblies (EMAs), including STEP-based assembly modelling, representation, planning and optimization of assembly sequences. Based on the author's previous work, the hierarchical relation model is used for a unified description of causal relations both on assembly level and on feature-based single part level. The generic product assembly model is organized in terms of STEP using mainly the entities of integrated resources and partially the self-defined entities necessary for assembly design and planning. With this representation, all feasible assembly sequences can be generated through reasoning and decomposing the levelled feasible subassemblies, and they are represented and visualized through a Petri net, that is, the assembly Petri net model is obtained. To obtain a good assembly sequence, the generated assembly sequences are evaluated and optimized by considering the assemblability and assembly sequence evaluation index. A prototype system is developed based on the proposed STEP-based framework for assembly planning. Finally, an industrial case study is provided.