Browsing by Author "Lee, CEC"

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Bottleneck-based group scheduling in a flow line cell
(1998-12-01)
Chen, YC
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Lee, CEC
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工業工程與管理學系
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Department of Industrial Engineering and Management
Load imbalance and bottleneck phenomenon frequently occur in a cellular manufacturing (CM) environment due to the similarity of process requirements. To alleviate the load imbalance problem, this study focuses on flow line cells and presents a two-stage exhaustive bottleneck-based group scheduling procedure (BGSP). The proposed procedure attempts to fully utilize the bottleneck machine and minimize the makespan and flow time. Until now, the extent to which bottleneck management influences group scheduling heuristics has seldom been mentioned. Also designed herein are a simulation model and the experimental environment. In addition, experimental factors such as setup-to-run time ratio, number of part families, and bottleneck-to-nonbottleneck load ratio, are examined as well. Moreover, two single-stage and five two-stage group scheduling rules discussed in previous literature are compared. The procedure proposed herein possesses the best average makespan, average flow time, and more robust than available procedures. Results in this study demonstrate the practical nature of bottleneck management on group scheduling in cellular manufacturing systems.
Pull system for control and dummy wafers
(2003-12-01)
Chen, HC
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Lee, CEC
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工業工程與管理學系
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Department of Industrial Engineering and Management
Various CD wafers (Control and Dummy wafers) are used in wafer fabrication to enhance product quality and process stability. Most wafer fabs downgrade used CD wafers into other functional ones and then recycle them to reduce costs. Wafer costs increase with wafer diameter, and thus the downgrading mechanisms and inventory control of CD wafers have become increasingly important to fab performance. Wafer fabs now are willing to seriously consider CD wafer management but CD wafer management remains neglected in the literature. This study presents a novel pull system focusing on inventory and downgrading management of CD wafers. The proposed system in this study intends to reduce the WIP level of CD wafers, increase recycled usages (number of times CD-wafer lots are recycled) before scraping, and reduce machine delay ratio without lowering the product wafer throughput rate.