| The traditional economic production model assumed that production system is perfect, in fact, many kinds of machine failures would happen, such as machine shut-down and defective products. The main characteristic of the short life cycle products is the nonlinear holding cost. This thesis introduced two kinds of machine failure problems to the EPQ model of the short life cycle products and compared the optimal production strategies between the short life cycle products and normal products.For the production system with possible problems of machine shut-down, we assumed that the time when machine shut down followed as a index distribution. A economic production quantity model was established to search the optimal lot sizing when the unit time cost was optimized. Backlogging strategy was used to cope with the shortages and a two-stage EPQ model was established. The shortages from the first stage would be replenished in the second stage. In practical production, the rate of machine shut-down is not immutable. Workers' skills, environmental conditions and the machine itself would affect the failure rate. Therefore, it is necessary to do the sensitivity analysis to discuss that what kind of adjustment enterprises should make to guarantee the optimal cost. For the production system with possible problem of defective products, we introduced an imperfect inspection system with two kinds of mistakes to make sure that every product would be inspected. Learning effect was used to cope with the ratio of defective products. A economic production quantity model was established to search the optimal lot sizing and optimal production frequency when the total cost was optimized. The optimal production strategy of the short life cycle products and normal products and the different impacts of learning effect on these two kinds of products were discussed. Some useful conclusions were proposed after numerical example and sensitivity analysis. |
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