Simulation Studies of Hybrid Pull Systems of Kanban and CONWIP in an Assembly Line

Abstract

Pull system is an important component of lean manufacturing that can effectively reduce typical wastes associated with push production systems, such as overproduction. Using Toyota’s Kanban system, a production line can be configured as a pull system to avoid unnecessary accumulation of Work in Process (WIP). Another common method to carry out a pull concept is the CONWIP line, which maintains a constant WIP level within a segment of production line. Both methods have proven effective, but they may have different characteristics. The objective of this paper is to explore the potential to combine Kanban and CONWIP methods into a robust hybrid pull system that preserves the advantages of both methods while minimizing the disadvantages of each individual method. A simulation study has been carried out based on a real-world assembly line. Various pull system configurations of the assembly line have been evaluated and compared in terms of WIP level, number of Kanban cards in system, and throughput. The study shows that the productivity of CONWIP configuration outperforms Kanban configuration in majority of scenarios; and the performance of a well designed hybrid system can be more robust to various scenarios, compared to Kanban and CONWIP system.