Card-based production control: a review of the control mechanisms underpinning Kanban, ConWIP, POLCA and COBACABANA systems

Since the emergence of Kanban, there has been much research into card-based control systems. This has included attempts to improve Kanban and/or develop alternative systems, particularly ConWIP (i.e. Con stant W ork- I n- P rocess), POLCA (i.e. P aired-cell O verlapping L oops of C ards with A uthorisation) and COBACABANA (i.e. Co ntrol of Ba lance by Ca rd- Ba sed Na vigation). Yet, to date, no unifying review of the mechanisms underpinning these systems has been presented. As a consequence, managers are not provided with sufficient support for choosing an appropriate system for their shop; and researchers lack a clear picture of how the mechanisms compare, leading to several misconceptions. This paper reviews the control mechanisms underpinning the Kanban, ConWIP, POLCA and COBACABANA systems. By comparing the 'control mechanism' (i.e. the loop structure and card properties) and 'contextual factors' (i.e. routing variability, processing time variability, and whether stations are decoupled by inventory or the flow of jobs is controlled), we provide managers with guidance on which system to choose. For research, we show for example that most criticisms put forward against Kanban systems, e.g. to justify the development of ConWIP, POLCA or COBACABANA, only apply to work-in-process Kanban systems and not to production Kanban systems. Future research directions for each control system are outlined.