The Influence of Cost, Function and Process Capability on Tolerance Available to Purchase

Some studies concerned with the allocation of tolerances have been published, but only a few deal with both cost and function. In order to overcome this drawback, and to tighten the liaison between design and production, work has been carried out in the area of tolerance, with cost, function and process capability the main parameters in mind. Such work is discussed, where the problem covered is the manner of specifying the component tolerances of an assembly, so that the resulting functional variables of the assembly can meet their respective functional requirements, and the cost of manufacturing all the components to their respective tolerances is minimised. It shows that, when manufacturing cost information and process capability information are available, functionally correct design at minimum cost can be achieved. Furthermore, how statistical analyses of the manufacturing processes involved can lead to the relaxation in requirements, thus, promoting industrial harmony while, at the same time, maintaining the desired levels of product quality and reliability, is shown.