Geometrical Variation Mode Effect Analysis (GVMEA) for Split Lines

Abstract

The visual quality is a large contributor to the over-all quality impression of a product. For a complex, assembled product the visual quality is often judged by the geometrical quality in its split lines, where parallel split lines with small gaps and no flush usually are the desirable outcome. The gap, flush and parallelism in the split lines are affected by the variation on part level, variation in the joining process and the design concept itself. The visual sensitivity of a split line is also important in this context, e.g. if a split line is hidden, its visual quality is not important. In this paper, the ideas from traditional failure mode effect analysis (FMEA) are adapted to a geometry assurance context, where the visual impression of split lines is in focus. The visual sensitivity, as well as the probability of non-nominal outcomes, are included in the analysis. The probabilities of non-nominal outcomes are calculated using advanced non-rigid variation simulation based on Monte Carlo simulation combined with finite element analysis. In this way, all forces and bending due to joining and non-nominal geometries can be included. The goal of the suggested geometrical variation mode effect analysis (GVMEA) is to rank the split lines from the most critical one to the least critical one for the visual quality of a product. This is done by calculating a risk priority number for each split line. In this way, the split lines with the highest risk to impair the visual quality of a product can be identified and hopefully fixed. The method is demonstrated on a ready-to-assemble chest, i.e. on an example from the furniture industry.