REDUCTION OF POSITION ERROR OF KINEMATIC MECHANISMS BY TOLERANCE ANALYSIS METHOD, PART I: THEORY

Abstract

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