The impacts of variability on scheduling approaches for a printed wiring board assembly operation

Unrelated parallel machine scheduling problems have been well-studied for several single objective cases under deterministic processing conditions. While these problems are adequate for some manufacturing environments, there are situations where multiple objectives need to be considered. We report on a case for a Japanese printed wiring board manufacturer's drilling operation, which is measured on five key performance objectives and which is subject to processing time variability and random equipment breakdowns (usually in the form of jams). This research presents and evaluates an optimization approach against three dispatching heuristics to determine how these different scheduling approaches are impacted by processing time variability and equipment breakdowns and to determine which perform best under various levels of uncertainty.