| Summary: | 碩士 === 中原大學 === 工業與系統工程研究所 === 99 === The traditional Economic Production Quantity (EPQ) considers the perfect production process without defects and space capacity limit. This research relaxes some EPQ assumptions which include perfect items and unlimited space capacity. As time goes on, the production process will shift from an in-control state to an out-of-control state. The elapsed time until the production process shifts is assumed to be a random variable with a known exponential distribution. Thus, a fixed portion of items produced is defective. This research is concerned with in-process inspection, rework, scrap, space capacity and economic joint replenishment quantity of raw material in a batch production system. The objective is to determine an optimal production cycle time and the replenishment quantity that minimize the expected average cost per unit of time. Then based on renewal reward theorem, expected average cost per unit of time can be obtained by dividing the expected total costs per renewal cycle to the expected duration of a renewal cycle. The bisection method is employed to find a near-optimal solution for the model. By approximating exponential function included in the objective function, a closed-form solution can be developed. A genetic algorithm heuristic is implemented to verify the effectiveness of the solution procedure we proposed in this research. Finally, to demonstrate the validity of the model, a numerical example is provided to illustrate the model. Meanwhile, sensitivity analysis is performed to give management insight.
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