Simulation of the geometrical defects of manufacturing

Abstract

The complexity of a multi-stage machining process makes it very difficult to assess process plans, from a geometrical point of view. Today, repeated trial runs or very simple simulations are the methods applied to assess a process plan before production release. Due to the cost and time involved in trial runs and the inaccuracy of current simulations, an alternative means should be investigated. This could involve developing accurate 3D simulation methods. This paper proposes a detailed mathematical formulation of tolerance analysis based on searching for the worst case. The performance of two current optimization methods for worst case identification (genetic algorithm and sequential quadratic programming) will be explored through two 3D examples. This paper builds on the model of manufactured part (the MMP) previously proposed by the authors for modeling the different geometrical deviation impacts on the part produced (error stack-up) in a multi-stage machining process. The model cumulates the impacts of various sources of manufacturing errors, hence enabling tolerance analysis. Previously, the same authors also presented a generic formulation for tolerance analysis based on searching for the worst case using the MMP.