Method for Geometric Variation Management from Key Characteristics to Specification

For complex product like aircraft or car body, producibility improvement has to go through a better product assemblability. In order to reach this goal, effects of manufacturing variations have to be reduced. We propose to describe in this paper a pragmatic method analysing the impact of geometrical variations on product Key Characteristics (KC). The main idea of this method is that the flow of geometrical variations belongs to the assembly process. To identify the most promising assembly sequence allows then to minimise impact of geometrical variations. Based on this principle, the first step of the method is to identify where are the Key Characteristics for the product. This identification uses a top-down process going from functional product requirements to geometrical characteristics. Relative to this KC identification, our method performs a qualitative product analysis in order to eliminate the worst assembly sequences. This analysis is based on oriented graphs. At last a quantitative analysis allows to select the most promising assembly sequence. This integrated method has been performed with success on aircraft assemblies and has improved aircraft producibility.