Cost–Tolerance Function. A New Approach for Cost Optimum Machining Accuracy

Abstract

Tolerances contribute both to the accuracy and quality of a mechanical product and to the manufacturing cost of the product. Tolerance optimisation taking into account the relevant machining cost is effected by making use of various empirical and/or analytical and computer-aided techniques and methodologies, with varying degrees of success. Among them, cost-tolerance functions play a major role. On the basis of the available industrial knowledge and the published work, the paper presents the development of a new analytical cost-tolerance model. This model is more inclusive than the previous ones, has a wider field of applications and, as it is shown, produces results that lie closer to industrial practice. It takes into account the size of the toleranced dimension, the tolerance size, the size of the initial tolerance before machining starts, the size of the workpiece surface that has to be machined to the specified tolerance(-es). Its use is demonstrated and discussed in an application example.