Manufacturing signature and operating conditions in a variational model for tolerance analysis of rigid assemblies

The need of an univocal language for geometrical product specification considering all steps of the product life-cycle such as design, manufacturing, and inspection is inevitable. Most models for computer aided tolerancing proposed by researchers and used in industry do not fully conform with standards. Moreover, most of them make severe assumptions on observable geometric deviations and can therefore hardly handle all kinds of 3D tolerances. These lacks inspired the idea and the development of a discrete geometry framework that is capable of considering geometric deviations of different stages of the product life cycle and is versatile regarding current and future tolerancing standards. This work uses a point cloud-based geometry representation scheme to implement the pattern left on the surfaces by a manufacturing process; then this scheme has been inserted in a variational approach for tolerance analysis. Moreover, gravity and friction among the parts to assemble have been simulated too. In this way a new Computer Aided Tolerancing (CAT) simulation tool has been developed; it approaches reality more than existing software packages do. To verify the effectiveness of the new CAT simulation tool, it has been applied to two case studies. The obtained results have been compared with those due to a geometrical model that has been developed by simulating what happens among the parts in the actual assembly. The obtained results show how the new CAT simulation tool gives results nearer to reality than literature models do.