Comparative evaluation of tolerance control chart models

A comparative evaluation of two widely used tolerance stack up models is carried out. Experimental metal cutting tests of resultant dimensions obtained under one and two fixturing set-ups are used to test the underlying assumptions behind the Wade and Bourdet tolerance chart models. Resultant dimensions obtained under a single fixturing set up are found to be highly correlated and free of fixturing error; their treatment under the Wade model can thus lead to overly conservative tolerance allocation which may reject an otherwise feasible process plan. The results of the experimental evaluation lend support to the Bourdet deterministic treatment of such resultant dimensions. However, the probabilistic approach proposed by Bourdet does not guarantee a solution.