Comparative study of tolerance on cost for various metal-removal processes

Abstract

Tolerance design has been identified as one of the key areas to realize the objective of producing quality goods at affordable cost. The impact of tolerance on the cost of manufacture for various metal-removal processes are shown by cost models. These cost models are in turn used in tolerance design to arrive at the relative cost of manufacture to various tolerances. Most of the cost models available untill recently were based on data from industries in the USA. However, Gunasekaran et al. (Gunasekaran, K., Neelakrishnan, S., Ragu, K. and Mohanram, P.V., Influence of tolerance on cost for various manufacturing processes, in National Conference on CAGQ -2004, Thiagarajar College of Engineering, Madurai, India, 2004) presented the relative cost of tightening manufacture in Indian industries for attaining various tolerance values in Indian rupees and the results have been presented in graphical format. These formats are useful in determining the cost involved when tolerance synthesis methods are used to allocate tolerances to parts. In order to have an understanding of the costs involved to manufacture to a specific tolerance among the job shop-type and organized sector found in Indian industry, the cost versus tolerance data presented by Gunasekaran et al. ( job-shop industry) have been compared with further data gathered by the present authors. In addition, the comparison includes the cost curves presented by Chase et al. (Chase, K.W., Greenwood, W.H., Loosli, B.G. and Hauglund, L.F., Least cost tolerance allocation for mechanical assemblies with automated process selection, J. Manuf. Rev. ASME, 1989, 2(4), 49-59). This is especially useful in analysing the differences in sourcing from a job shop versus the organized sector. In addition, the results that are displayed graphically are also compared with the cost models that already exist. In addition, one of the benefits of the cost curves is illustrated with a case study of a simple component.

Allocation of geometric tolerances in one-dimensional stackup problems

“…A first issue in the extension of the allocation problem is that manufacturing costs must now be related to all the standard geometric controls. Cost-tolerance functions have been proposed for various types of features and machining processes, considering position tolerances on holes [12] and profile tolerances [13]. To cover a wider range of cases, discrete cost-tolerance data have been published under given assumptions regarding machining and inspection processes [14][15][16].…”