Design for tolerance of electro-mechanical assemblies

Tolerancing decisions during the design of electromechanical products profoundly affect cost and quality. Existing approaches to tolerance analysis and synthesis entail detailed knowledge of geometry of the assemblies and are mostly applicable during advanced stages of design, leading to a less than optimal design process. During the design process of assemblies, both the assembly structure and associated tolerance information evolve continuously and significant gains can be achieved by effectively using this information to influence the design of the assembly. Motivated by this, we identify and explore two goals of research that we believe can expand the scope of tolerancing to the entire design process. The first goal is to advance tolerancing decisions to the earliest possible stages of design. This issue raises the need for effective representation of tolerancing information during early stages of design and for effective assembly modeling. The second goal addresses the appropriate use of industry best practices and efficient computational approaches for tolerance analysis and synthesis. Pursuit of these goals leads to the definition of a multi-level approach that enables tolerancing to be addressed at successive stages of design in an incremental, continuous ongoing fashion. The resulting design process, which we call the Design for Tolerance process, integrates three important domains: (1) design activities at successive stages of design; (2) assembly models that evolve continuously through the design process; and (3) methods and best practices for tolerance analysis and synthesis. We demonstrate major steps of our proposed approach through a simple, yet illustrative, example.