Determining Economic Manufacturing Quantity for an unreliable manufacturing system in discrete time setting

The paper considers an Economic Manufacturing Quantity (EMQ) problem for a failure-prone manufacturing system in which the production facility may fail at most once during a production cycle. In a discrete time framework, we formulate the model under general-failure and -repair (corrective) time distributions based on the Net Present Value (NPV) approach. As a special case, the model with general failure and constant repair times is considered. The traditional long-run average cost model is obtained from the NPV model by taking limitation on the discount rate. The criteria for the existence of a local optimal solution are derived for the NPV as well as the long-run average cost models. With numerical examples, the optimal production policies are determined and sensitivity of some model-parameters are examined. A comparison of the outcome of the proposed model with the one obtained by time discretisation in the corresponding continuous time model is also made.