Re-Design of Mechanical Assemblies using the Unified Jacobian-Torsor Model for Tolerance Analysis

摘要

This paper describes how the unified Jacobian-Torsor model can be used for the redesign of assembly tolerances. Through a numerical and graphical approach, the designer is guided into choosing his tolerances. After having identified a functional requirement (FR) and the functional elements (FEs) of the dimensional chain, it becomes possible to compute the percentage contribution of each FE to the FR. A percentage contribution chart tells the designer how each dimension has contributed to the total FR. Once these contributions have been identified, we proceed to modify the most critical tolerance zones to respect the requirements imposed by the designer. The results are evaluated by comparing the predicted variation with the corresponding specified design requirements. Then, the contributions can be used to help decide which tolerance to tighten or loosen. This study has been developed for Worst-Case approach. Finally, an example application is presented to illustrate our methodology.