Restricted Work-In-Process, A study of differences between Kanban and CONWIP
This article presents a simulation study over a small supply chain, where the amount of work-in-process (WIP) is restricted. The supply chain consists of five linked machines (or production facilities) with stochastic operation times. A number of test cases are made where the number of jobs in the machines and the buffer areas are restricted. The restrictions are designed both in the Kanban way, linked to every machine, and in the CONWIP way, connected only to the total production line. But no Kanban-cards and no Kanban-cells are involved in our study, just restricted inventories between the machines. With the same amount of limited WIP CONWIP control, compared to Kanban control, presents a higher throughput rate, less time between jobs out, but the jobs stay on average longer in the system. The stochastic operation times cause that the upstream machine sometimes consumes the jobs in a rate that the downstream machine does not catch up with, therefore all available storage room temporarily are not used. With the same variation in operation times the same amount of real average WIP presents the same amount of average outflow per time unit, despite of a Kanban or CONWIP control. But Kanban control causes a lower utilisation of present available storage room and storage equipment than CONWIP. The coefficient of variation of the lead-times increases when WIP increases; this is very difficult to handle in practical applications. Restricted WIP that shortens the lead-time and decreases its variation is more important than if it is a “push or “pull system. Finally it is argued that CONWIP control is to prefer over Kanban control theoretically, but practically there is a lack of CONWIP installations.
Manufacturing Supply Chain Management CONWIP Kanban Work-In-Process
Jan-Arne PETTERSEN Anders SEGERSTEDT
Narvik University Collage,IBDK,Postboks 385,8505 Narvik,Norway Luled University of Technology,Industrial logistics,S-97187 Luled Sweden
国际会议
北京
英文
2007-05-30（万方平台首次上网日期，不代表论文的发表时间）