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The wafer fabrication is in the blooming state such that
maximizing capacity utilization to promote profits is needed.
However, the increasing capacity utilization rate may cause the
results of large WIP quantities, long flow times,..., and etc.
Based on the concepts of WIP control and output balancing, this
thesis attends to develop the production planning model for
wafer fabrication factories with consideration of the
production rate, WIP level, and the flow times of products.
This model is divided into three stages: master production
schedule(MPS), detailed schedule, and shop floor control. These
three stages construct a hierarchical relationship, that exists
in the setting of objective for each stage. That is,
accomplishing the planning output of the upper stage is the
planning objective of a lower stage. The MPS stage considers
the desired product mix and output volume to set the level of
WIP in each planning period--4 weeks. Under the situation that
the production mix, output volume, and WIP level are fixed, the
flow time thus can be controlled in the shop floor control
stage to satisfy the MPS. The detailed scheduling stage then
plans the work that should be done in a week. It uses the
number of times passed through the bottleneck machines(number
of layers) to express the status of WIP and the output.As a
result, the shop floor control stages controls the output and
WIP by layer.The flow time, and the WIP level can thus be
actually controlled such that the MPS can be achieved.
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