2006 Volume 57 Issue 4 Pages 278-288
The configuration of a production system affects its performance. There has been much research on configuring production systems, such as assembly line balancing and cell formation. Under a specified configuration, the performance of the production system is affected by production ordering and buffer allocation. Ordering systems determine the order timing and materials quantity released for each stage of a multi-stage production inventory system and buffer volumes are often allocated; just-in-time (JIT) ordering systems determine them on the basis of actual demand. The Kanban system was developed by a Japanese automobile manufacturer as an original JIT ordering system. Alternatives include the constant work-in-process (CONWIP) system and the concurrent ordering system. The performance of JIT ordering systems is analyzed and compared with other systems. In most of the previous literature on JIT ordering systems, stable changes in demand have been assumed, and the influence of unstable changes in demand had never been analyzed. Based on this background, some reactive systems have been proposed for the Kanban and CONWIP systems. In reactive Kanban or CONWIP systems, unstable changes in demand are detected, and the number of Kanbans and the buffer size are adjusted as a reaction to the changes detected. However, if only the number of Kanbans or the buffer size is adjusted, adaptability is limited. Recently, reconfigurable manufacturing systems (RMSs) have been introduced, and systems which can adjust the configuration in response to environmental changes are likely to be realized. Therefore, this paper introduces dynamic line balancing and buffer allocation in a RMS controlled by the CONWIP system. In the proposed system, unstable changes in demand are detected by exponentially weighted moving average (EWMA) charts, the configuration of the production system-that is, the number of stages and buffer size-are altered in response to the unstable changes detected, and work elements are allocated to each stage by balancing the line. The effectiveness of the proposed system is analyzed and compared with that of the previous system using simulation experiments.
