Maximizing Throughput in Large Robotic Cells at FSI.

The article discusses the use of an optimization approach to improve scheduling within robotic cells for FSI International Inc., a company that designs and manufactures robotic cells for wafer-fabrication companies. A robotic cell is a manufacturing system used in a variety of industries, including wafer fabrication. A wafer-fabrication cell contains several robot-served processing stations and produces identical wafers repetitively. Each wafer is processed through processing stations or stages as in a stage flow shop, and there are no buffers at or between the processing stations. Since a single type of wafer is produced, the optimal schedule is simply the sequence of robot moves that maximizes the throughput or, equivalently, minimizes the per-unit cycle time or the average time to produce a part in steady state. Since wafers are very valuable, even a small increase in throughput may lead to a substantial increase in profit. Consequently, throughput is a critical issue for the wafer-fabrication companies that are FSI's clients.