Geometric model and analysis method of form and location tolerance in digital environment

On account of the geometric tolerance-included tolerance analysis problem of complex assembly, this paper puts forward and establishes the dimensional element model of geometric tolerance in digital environment. By analyzing the nature of geometric tolerance and its influence upon assembly, this paper specifies geometric tolerance with dimensional element, and specifies the tolerance zone with the constraint relations between the nominal dimensional elements and the normative dimensional elements, so as to convert the value definitions into geometric form feature representation of product digital model, and realize quantitative analysis in digital environment. Furthermore, the paper drives the model and measures its influence on the closed-loop by making use of dimensional element chain analysis (DECA), which is based on CAD system and product digital model, to realize the geometric tolerance-included assembly tolerance analysis. This method is realized in UG system and is verified by examples.