Abstract: In order to realize the automatic generation of dimension chain and geometric tolerance items in incremental growth design process, the evolutionary tolerance design strategy and its characteristics are studied on the basis of automation technology in the product structure design. The theoretical foundation for the growth design as well as the hierarchical tolerance evolutionary model is given. With the evolution of structure design in top—down style，the tolerance design develops and evolves in the same way, that is, following the evolution of product structure, tolerance grows from the initial accuracy requirements to the final state, during which the basic units in structure growth—functional surfaces and their nominal features are used as the tolerance evolutionary carriers. The basic method for the construction of two-layer correlation network including assembly network based on functional surfaces and constraint network based on nominal features is proposed, and the tolerance assertions to assist tolerance evolutionary design are given. The basic process for evolutionary design of dimensions chain and geometric tolerance based on the two-layer correlation network are presented. The tolerance design of a piston clamp is used as an example to demonstrate the successful application of the proposed tolerance evolutionary strategy in the incremental product growth design process..

Key words: Dimension chain design, Evolutionary tolerance design, Functional structure design, Geometric tolerance design, Incremental growth design