This paper addresses the issue of investing in reduced setup times and defect rates for a manufacturer of several products operating in a JIT environment. Production cycle times can be shortened by investing in setup time and defect rate reductions, respectively. The objective is to determine optimal levels of setup time and defect rate reductions along with the corresponding optimal levels of investments respectively, and the optimal production cycle time for each product. The problem is constrained by demand requirements, process improvement budget limitations, and manufacturing and warehousing capacity constraints. We consider the cases of product-specific quality improvements and joint-product quality improvements. A general nonlinear optimization models of these problems are formulated. A convex geometric programming approximation of these models is developed respectively, in order to solve them. The approximation can be made to any desired degree of accuracy. Our empirical findings provide insights into a number of managerial issues surrounding investment decisions in product-specific quality improvements and setup reductions due to a product redesign as well as in joint-product improvements due to a process redesign.

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Keywords Geometric programming, Lot scheduling, Production planning, Quality improvement, Setup reduction
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Journal European Journal of Operational Research
Diaby, M. (Moustapha), Cruz, J.M. (Jose M.), & Nsakanda, A. (2013). Shortening cycle times in multi-product, capacitated production environments through quality level improvements and setup reduction. European Journal of Operational Research, 228(3), 526–535. doi:10.1016/j.ejor.2013.02.026