Automatic optimal tolerance design for related dimension chains

An optimal design approach to tolerance allocation is presented. To avoid design conflicts that may occur with current optimal tolerance design methods, the general formulation of optimal tolerance design for multiple and related dimension chains has been introduced. A method, which automatically generates the optimization objective function, incorporating manufacturing knowledge, has been developed. The method associates each design tolerance with an appropriate production cost-precision model, using an expert system. It has been implemented using the Davidon-Fletcher-Powell optimization technique and a dedicated inference program with the IGES interface to a CAD system. A design example is used to illustrate the approach.