Kanban

Kanban — Japanese for 'visual card' — is a pull-production mechanism formalised by Ohno (1988) within the Toyota Production System (TPS) framework. It has two basic types: (1) production kanban — signals a station to 'produce so many of this part'; (2) withdrawal (transport) kanban — authorises material movement from one station to another. The essence of the system: no station produces on its own; it produces only on the kanban signal arriving from the next station. This is the opposite of push production and provides a mathematical ceiling on WIP — the total number of kanban cards in the system fixes the maximum WIP. Kanban is the operational implementation tool of JIT and Lean Manufacturing. In an SMB context kanban is applied with either physical cards (boards, bin systems) or electronic kanban (e-kanban); the latter is preferred for supplier integration. Card-count formula: N = (D × LT × (1+α)) / C, where D is average demand rate, LT is replenishment lead time, α is a safety factor, and C is the parts-per-card capacity. The pull interpretation of aggregate production planning, the multi-item kanban adaptation of the Joint Replenishment Problem, and WIP-capped variants of job-shop scheduling all rest on the kanban principle. References: Ohno 'Toyota Production System: Beyond Large-Scale Production' (1988); Sugimori et al. (1977); Monden 'Toyota Production System' (1983).