It is practically impossible to manufacture a component exactly with the required dimensions. Therefore for each part dimension, a tolerance limit is prescribed. Also for all assemblies, a limit of variation is prescribed for a specified parameter of the assembly which is referred to as the assembly specification. In this research the Direct Linearization Method (DLM) is used to determine the distribution limit of the assembly specification in terms of part tolerances. It has been assumed that the assembly is a mechanism with flexible parts; therefore, in addition to manufacturing tolerances, external loading will impose external variations on part dimensions which result in extra errors on assembly specification. The effect of flexible components will cause change in mean, variance and correlation of the assembly specification. FEM is used to model the mechanism in order to compute part dimension variations under external loading. The percent contribution of each input variable on the assembly specification is obtained by the proposed multiple linear regression model. It has been proposed an optimization algorithm to assign part tolerances which minimizes manufacturing expenses while the maximum error of the assembly specification is kept within the desired limit.

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