Abstract: An automatic generation method of 3D assembly dimension chains is proposed based on 3D CAD models. Starting with the definition of assembly performance feature (APF), CAD models are deeply analyzed and pre-treated to get the data hiding in the models needed by tolerance analysis. Then based on graph theory, feature-dimension adjacent matrixes, feature-assembly constraint type adjacent matrixes and assembly relation transfer graphics (ARTG) are built, which can express the information transfer process of parts, features, as-sembly constraints and dimensions in an assembly. Finally, 3D assembly dimension chains are classified into two types, ex-plicit and implicit chains. For explicit chains, tolerance chain graphs and equations can be directly got from ARTG through searching connected routes. For implicit chains, the conception of degree of dimension direction unlikeness and the searching policy which gives priority to closing-loop-direction are proposed, and finally tolerance chain graphs and equations can be achieved by the method of building transition tolerance chain. The method is validated by our own-developed 3D assembly dimension chain automatic generation system.

Key words: 3D assembly dimension chains, Assembly performance feature, Assembly relation transfer graphics, Transition dimension chain