Adaptive ConWIP: Analyzing the impact of changing the number of cards

In response to fast changing environments, adaptive ConWIP pull control systems have appeared as an efficient approach to reduce work in process while maintaining a good customer satisfaction. The number of cards is adjusted as a response to detected changes in the demand. However, in a real-life environment, adding and retrieving cards can have undesirable effects and disturb the manufacturing system. Our literature analysis underlines that, although numerous studies have investigated adaptive mechanisms, none of them seems to take into account the consequences of the numerous changes in the number of cards. In this article, we do not only consider the usual costs, but also the number of changes induced. A ConWIP example, often used in the literature, is studied using simulation optimization on the basis of these two considerations. Our results point out that the reduction of costs is achieved through a tremendous amount of changes, which can lead to system instability. They illustrate that, when implementing an adaptive ConWIP system, practitioners should carefully take into consideration the consequences of modifying the number of cards. Depending on the manufacturing system considered, we argue that several criteria should be used to better decide when changing this number is really necessary.