Generalized Kanban-Loops for Multi-stage Manufacturing Processes

Abstract

The Toyota Kanban system is known as one of the most effective production systems for controlling materials flow in multi-stage manufacturing processes. Materials flow is triggered by the input flow from subsequent stages using Kanban-loops. The CONWIP system and the nested Kanban-loop system were proposed as improved versions of the Toyota Kanban system. However, these studies used different structures of Kanban-loops under different models. In multi-stage manufacturing processes, there are many points just before and after each stage that are able to trigger the flow. In this paper, a multiple Kanban-loop system is proposed to generalize the Kanban-loop structure in multi-stage manufacturing processes. The multiple Kanban-loop system has all the possible loops beginning from the output position of each stage and ending at the upstream stages. The Toyota Kanban system, the CONWIP system and the nested Kanban-loop system can be expressed as a special version of the multiple Kanban-loop system. Under the objective functions of system productivity and total work-in-process, it is shown that the nested Kanban-loop system can achieve optimal materials flow in multi-stage manufacturing processes.