Evaluation of relations and accumulations of geometrical deviations in multi-stage manufacturing based on Skin Model Shapes

Abstract

The inevitable existence of variations in manufacturing processes leads to deviations in the geometrical result of the manufactured products. As a result, every part produced is shaped uniquely regarding its geometrical properties and has both systematic and random deviations. In addition, local and global deformations can have a significant impact on product quality and lead to complex relationships between deviations. Furthermore, the deviation accumulations occurring in multi-stage manufacturing must be considered in the tolerance procedures. Existing methods, especially in manufacturing tolerancing, assume certain simplifications, so that comprehensive evaluation and integration, as well as their complete metrological verification are hindered.This paper presents a method that considers manufacturing variations separately for each process step and accumulates the resulting geometrical deviations, based on the extension of established methods for Skin Model Shapes. The relationship between deviations and their accumulation can be quantified, which provides essential knowledge especially for manufacturing tolerancing. In addition, it complies with Geometrical Product Specifications and Verification Standards, which offers considerable benefits for geometric variation management during the whole product life cycle. Finally, a case study is presented to illustrate the approach.