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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 40595 (01)
- University: Sharif University of Technology
- Department: Industrial Engineering
- Advisor(s): Haji, Ali Reza
- Abstract:
- This research attempts to develop the optimal solution for an inventory problem consisting of a single machine which produces items some of which may be defective. We assume that no shortages are allowed and all defective items are to be reworked. Setup cost for rework and waiting time of defectives are considered. This research consists of two different parts. In the first part we consider two different policies where in the first policy in each cycle after the regular production the machine is setup for the rework of defectives of the same cycle. In the second policy several cycles constitute a period. All the defectives produced in the period are reworked in the last cycle of that period. At the end of the rework cycle the whole process starts all over again. One significant feature of this work is that we do not impose any restriction on the length of the period. We derive the total cost function which includes the setup cost for rework and regular production, waiting time cost of defectives for rework, rework and regular processing costs and holding cost. We then derive the optimal solution of the total cost function for the two different policies. The second part deals with the issue of economic batch quantity (EBQ) in a single machine system in which defective items are produced in each cycle of production. The accumulated defective items produced in a period, consisting of several equal cycles, are all reworked in the last cycle of this period called the rework cycle. At the end of each period the whole process will start all over again. We assume that there is a limitation on the total defective items. We also do not adopt the restriction that the rework process rate be equal to the normal production rate. In addition we assume that there is a set up time for rework process. Further we assume that the number of rework cycles be as small as possible, which is mainly due to changeover costs needed for going from normal production to rework as well as special attention required for rework to satisfy the zero defect criterion. Furthermore, for the ease of production and resource planning, the rework cycle has to have the same length as the other cycles. For this system, assuming no shortages are permitted we obtain the economic batch quantity which minimizes the total cost of the system. Finally, Due to the nature of rework process we do not restrict the rework rate to be equal to normal production rate or constant and assume that it is a random variable with an arbitrary distribution function. We also assume as it is true in most real world situation that the unit rework processing cost need not to be equal to unit normal processing cost.
- Keywords:
- Rework ; Economic Batch Quantity ; Imperfect Production
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