The Design of Machine Units Pruning Mechanism for a Wafer Fab
| Autor: | Jui-Chun Liu, 劉睿鈞 |
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| Rok vydání: | 2003 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 91 Wafer manufactures usually face a strategy of pruning machine units for the need of selling or leasing machines. However, different machine type and corresponding units are pruned from the shop floor will cause different effects on the production performance. Moreover, various product mix and throughput target will also cause different effects on loading of each individual workstation. Therefore, considering the variation of product mix and throughtput target, this thesis aims to design the machine units pruning mechanism for maintaining system throughput target and delivery rate. Based on the concept of Theory of Constrains (TOC), bottleneck wandering must be prevented. The mechanism first estimates the loading of each workstation under a given product mix and throughtput target to determine the least machine units needed. Second, the increment of the production cycle time as one machine unit of a specific workstation was pruned must be estimated. The block-based cycle time (BBCT) methodology, which considers the waiting time due to machine loading and congestion of production flow, is used. Next, one machine unit of the workstation which has the lowest effect on production cycle time is pruned. Repeat the above steps of evaluation, until the production cycle time has reached the upper limit for achieving the target of delivery rate. At last, repeat the above procedure for each possible product mix and throughtput target respectively. Then, all the results are collected so as to generate the machine set being pruneable. Simulation experiments reveal that with machine units pruning mechanism, not only the system can have its throughput reaching the planned target, but also can control the delivery rate within acceptable range. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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