Angus Jeang
The Journal of Mechanical Science and Technology, vol. 23, no. 1, pp.237-245, 2009

Abstract : Product designers are always concerned that a newly developed product is properly performing its functionality for its intended life under consumer usage conditions. It is known that the failure rate is increased in the late time of product life cycle as the consequence of deterioration being built up. Namely, continuous changes may take place in the parameter values of product and the product application may be ended before expiration of its intended life. Hence, a design that considers parameter compensation to extend using time becomes an important factor in earlier stages of product design. Other than the parameter values, the tolerance values are an important element affecting the product performance, which are also needed to be decided appropriately. In this paper, an optimization model considers minimizing the total cost, which includes material cost, inspection cost, quality loss, failure cost, and tolerance cost by conducting concurrent optimization of the decision variables, initial setting, process mean, process tolerance, and using time. The design constraints are the restrictions resulting from process capability limits, functionality requirements, and quality necessities. The software GAMS was used to find optimal values for the decision variables of interest. Finally, an example of various components and subassemblies under deterioration process is presented to explain the proposed model and sensitivity analysis on some decision variables is performed.

Keyword : Quality loss; Tolerance cost; Deterioration; Product life; Optimization