INCLUDING GEOMETRIC FEATURE VARIATIONS IN TOLERANCE ANALYSIS OF MECHANICAL ASSEMBLIES

Geometric feature variations are the result of variations in the shape , orientation or location of part features as defined in ANSI Y14.5M-1 982 tolerance standard. When such feature variations occur on the mati ng surfaces between components of an assembly, they affect the variati on of the completed assembly. The geometric feature variations accumul ate statistically and propagate kinematically in a similar manner to t he dimensional variations of the components in the assembly. The direc t linearization method (DLM) for assembly tolerance analysis provides a means of estimating variations and assembly rejects, caused by the d imensional variations of the components in an assembly. So far no gene ralized approach has been developed to include all geometric feature v ariations in a computer-aided tolerance analysis system. This paper in troduces a new, generalized approach for including all the geometric f eature variations in the tolerance analysis of mechanical assemblies. It focuses on how to characterize geometric feature variations in vect or-loop-based assembly tolerance models. The characterization will be used to help combine the effects of all variations within an assembly to predict assembly rejects using the DLM.