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In wafer plants, product will be manufactured through same process with different setups and specifications. This special manufacturing process is described as re-entrant flows. In photo process of wafer manufacturing, products is also restricted to be processed through same machine in each reentrance to improve quality. This phenomenon will cause scheduling in photo process being complicated and is proved to be a NP-hard problem. This research develops a mathematical model for photo process to minimize the makespan. A feasible solution is achieved using DBR (drum-buffer-rope) method. The results are compared to the optimal solution that is achieved using branch and bound algorithm. Our results show that DBR based method achieves a near optimal solution in shorter time. The results also indicate that DBR method can be useful in production scheduling with resource constraints.

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Different designs of manufacturing systems are adopted in industry today. A good manufacturing design should be flexible to compensate for uncertainties such as demand fluctuations and machine breakdowns. A new conceptual manufacturing system called Multi-Channel Manufacturing (MCM) is expected to provide flexibility and efficiency under uncertainties. This paper proposes the first approach to address the usefulness of MCM. This research tries to identify the key characteristics of MCM and the manufacturing environments for which MCM should perform well. Through simulation models, different manufacturing scenarios are analyzed and a suitable manufacturing system design for each scenario is identified. The simulation results illustrate that with limited material handling capacity and opportunities for setup time reduction, MCM can outperform other manufacturing formations.