Implementing the theory of constraints philosophy in highly reentrant systems

A significant challenge in implementing the Theory of Constraints in the semiconductor industry is the complex and reentrant nature of the manufacturing process. Managing a constraint or bottleneck in such processes is resultingly complex and is an ongoing topic of research. The paper describes a straightforward method to avoid starvation of possibly recurring bottleneck equipment. This method is not proximity sensitive, meaning that it does not act on material only if it is within a specified proximity of the constraint. This method is capable of reacting to changes in product mix and can act to correct line imbalances since it is based on real time data from the floor control system. The assertion is also made that for the case where a bottleneck has several occurrences in the product flow, all occurrences of the bottleneck must avoid starvation, not just the overall equipment queue. This affects the ability of the primary constraint to feed itself