Minimizing Geometric Variation in Multiusage Assembly Line by Geometrical Decoupling

Paper i proceeding, 2011

Geometrical part robustness is today used as an engineering criterion in many manufacturing companies. The goal is to minimize the effect of geometrical variation by optimizing the locating schemes for the parts. Several methods and tools are today present to support geometrical robustness optimization for parts but also for assemblies. In this paper focus is on geometrical decoupling, which is one parameter of geometrical robustness, of the different locating strategies in a complete assembly line. A goodness value is proposed that describe the level of geometrical couplings in a complete assembly line together with the part robustness value. By calculating this goodness value it is possible to predict the geometrical sensitivity of a complete assembly line as well as predicting the risk of geometrical variation on the final product. To illustrate the definition of this goodness value, and also the purpose of calculating it, a case study is used where a part of a sheet metal assembly line is described. Several different scenarios (assembly concepts) are applied to clarify the meaning and to validate this definition of the goodness value. The case study shows that the goodness value gives a good indication of the level of geometrical couplings within the assembly line and that this value could be used to evaluate different assembly concepts, with their locating concepts, against each other. The goal is to have a more robust and also geometrically decoupled assembly line which the root cause analysis in production and also optimizes the geometrical quality minimizing the effect of geometrical variation of the final product from the plant.