Kanban
看板·kanban·"signboard, billboard"
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Kanban is a visual signal system that triggers production or movement of materials based on actual consumption.
Definition
Kanban is a scheduling system that controls production and material flow by using visual signals—traditionally cards, but can be containers, electronic signals, or empty spaces. When downstream processes consume materials, the kanban signal triggers upstream processes to replenish. This creates a pull system where production is authorized by actual consumption rather than forecasts. Kanban controls work-in-process inventory by limiting the number of signals in the system—no signal, no production authority. The word kanban means "signboard" in Japanese, reflecting its visual nature.
Examples
A two-bin kanban system controls fastener supply. Each bin holds one day's consumption. When operators empty one bin, they draw from the second and place the empty bin in the return lane. The empty bin signals the supplier to replenish. With two bins circulating, supply never runs out while inventory stays minimal.
Key Points
- Kanban authorizes production only when consumption creates a signal
- WIP is controlled by the number of kanban in the system
- Kanban makes workflow status visual and problems obvious
- Requires stability and reliability—kanban exposes every problem
Common Misconceptions
Kanban is a production scheduling system. Kanban doesn't create schedules; it responds to consumption. The schedule is set by the downstream customer; kanban authorizes production to replenish.
Kanban works in any environment. Kanban requires underlying stability—reliable processes, capable quality, and reasonable demand patterns. Implementing kanban in chaos just exposes the chaos; the underlying problems must be addressed.