3-D Tolerance Design Based On The Dimensional And Geometrical Product Specification And Verification

The new generation of GPS(Dimensional and Geometrical Product Specification and Verification, GPS)is a set of uniformed and digitized specification standards for product design, manufacturing, and verification, which provides pre-conditions for the expression and transformation of tolerance in the computer and makes it possible for automatic generation of tolerance. On the basis of summarizing the latest research in GPS standard and tolerancing both at home and abroad, the technologies of tolerance specification and tolerance analysis and synthesis oriented the new generation GPS standard are studied. The main researches are as follows:(1)The basic theory of new generation GPS and some definitions consistent with new generation GPS standard of geometric product are expounded. The transformation between dimensional tolerance and geometric tolerance is presented by analyzing their relations.(2) The assembly position of the product is described with positioning graphs based on the classification and preponderance order of the positioning features. Patterns and methods of tolerance specifications on the positioning features in datum reference systems are expounded and additional specifications are presented by means of summarizing the position relations between different reference systems. The definition of invariant DOF and mark of tolerance zone are given. Then, general rules for selecting datum reference frame are studied. Lastly, a simple assembly example and tolerance specification results are presented.(3) The method of tolerance optimum allocation based on analysis line is presented. By using the method of analysis line to establish relations between geometrical functional requirement and the tolerances of positioning features, the transfer equation is obtained. The process of 3-D tolerance analysis is shown on an assembly example, thanks to displacement expression of different joints and tolerance accumulation results. And on this basis, tolerance cab be optimized in means of minimizing the total manufacturing cost because the transfer equation is regarded as constraints of optimization model and the results can be obtained by calculations.(4)The prototype system for computer aided tolerancing is preliminary developed using CATIA/CAA development environment and the workflow of this system is analyzed by an example.