Impact of investing in quality improvement on (Q, r, L) model involving the imperfect production process

This paper investigates the impact of quality improvement on the modified l ot size reorder point models involving variable lead time and partial backo rders. The formulated models include the imperfect production process and a n investing option of improving the process quality. The objective is simul taneously optimizing the lot size, reorder point, process quality level and lead time. We first assume that the lead time demand follows a normal dist ribution, then relax this assumption to consider the distribution-free case where only the mean and standard deviation of lead time demand are known. An algorithm procedure of finding the optimal solution is developed, and tw o numerical examples are given to illustrate the results.