Masters' Theses An Evaluation of Workload Limited Order Release Strategies considering Planning Stage in a Jop Shop
2015.07.29 12:28
| year | 1999 |
|---|---|
| author | Byeongdae Choi |
| Keyword | Order Review/Release, Dispatching rule, Production Control Policy, Simulation |
| Abstract | Two major activities in the manufacturing firm is the manufacturing planning and the execution/control on the shop floor. The integration of planning and execution/control under a common objective is a key factor which determine the success or failure of the business. Executable plan to cope with changing demand is possible through the correct master data and the predictable shop floor activities as well as the demand forecast ability. And the efficiency and stability of shop floor can be achieved through a stable and executable manufacturing plan. The interdependence between planning and shop floor activities may bring about a vicious circle of an uncertainty on the shop floor and a nervousness of planning. What is most important to escape from a vicious circle is to reduce and stabilize the lead time. Order Review/Release (ORR) System is the linkage between planning system and shop floor. Reduction of the waiting time on the shop floor, work in process and lead time variation may be achieved by adopting ORR strategies. ORR determines which orders are allowed to be released to the shop floor, at which and under what condition considering shop floor and order information. But researchers on the ORR do not agree on the effectiveness of ORR. Some say that the overall system flow time may be increased if ORR is adopted, but others say that ORR can reduce work in process, shop flow time and variation of flow time. The objective of this research is to clarify under what environments order release strategy is effective. First, this research examines the effectiveness of two shop floor control policies (five workload limited order release mechanisms and three dispatching rules) under two environmental variables(two shop utilization levels and three planned order release intervals from planning system to the Pre Shop Pool) in terms of eight performance measures relating to lead time, delivery and work in process. Second, this research examines the effects of plan smoothing to the ORR. Simulation study was conducted in a hypothetical job shop. The experimental results show that dispatching rule is much more important than ORR is in controlling the shop floor. But the results indicate that ORR can reduce mean shop flow time, average WIP and variation of shop flow time under such environments where utilization level is high and planned order is weekly released to the Pre Shop Pool. And the results also show that the effect of plan smoothing on the ORR is insignificant, which is inconsistent with the results of the previous researches. In conclusion, ORR is not a substitute but a supplementary policy of dispatching rule. By adopting ORR in addition to dispatching rule, it is possible to reduce shop floor time, work in process and deviation of lead time, especially under environments where planning system which release planned order periodically is present. |
| c | MS |
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