3D tolerance specification: an approach for the analysis of the global consistency based on graphs

During last years, several numerical methods have been proposed to accomplish analysis and synthesis of 3D tolerance chains. These methods allow predicting final assembly variations, starting from tolerance specification set defined at part level. Nevertheless, few specific methodologies are available today to check the global consistency of a tolerance specification set, related to a mechanical assembly. In this work, an approach to validate the global consistency of a 3D tolerance specification set is proposed. The approach is mainly composed by two different analyses. The first analysis is aimed to verify, at assembly level, the adequacy of a tolerance specification set by determining the assembly subsets of parts which influence each assembly key characteristic. The second analysis is aimed to verify the consistency of the tolerance specification set by using rules, mainly based on the TTRS theory. In order to show the effectiveness of the methodology, two case studies are illustrated by using a friendly graphical user interface (GUI) developed in MatLab® environment.