Buffer allocation, machine selection and preventive maintenance optimization in unreliable production lines

In this paper, we consider a serial production line consisting of n unreliable machines with n-1 buffers. The objective is to determine the optimal preventive maintenance policy, the optimal selection of machines and the optimal buffer allocation that will minimize the total system cost subject to a given system throughput level. We assume that the mean time between failures (MTBF) of all machines will be increased when performing periodic preventive maintenance. An analytical decomposition-type approximation is used to estimate the production line throughput. The optimal design problem is formulated as a combinatorial optimization one where the decision variables are buffer levels, types of machines and times between preventive maintenance. To solve this problem, a Genetic algorithm is proposed. A numerical example is presented to illustrate the model.