Definition
A kanban is a physical card (or electronic signal) that authorizes the production or movement of a specific part in a specific quantity. It is the operational mechanism that implements the pull principle within the Toyota Production System. When a downstream process consumes parts, the kanban attached to those parts returns upstream as authorization to produce or deliver more — nothing is produced without a kanban signal.
Kanban is not a standalone system. It is a tool within TPS that only works when its prerequisites are in place: leveled production, stable processes, reliable equipment, standardized work, and small lot sizes.
Japanese Origin
The word kanban (看板) is an everyday Japanese term meaning “signboard” or “sign.” The character 看 (kan) means “to see/look at” and 板 (ban) means “board” or “plate.” You see 看板 on shop signs, restaurant placards, and storefronts throughout Japan.
Taiichi Ohno deliberately chose this common word rather than a technical term. The tool should be simple enough that anyone on the factory floor could understand it immediately. Before TPS adopted it, kanban had zero manufacturing connotation.
History at Toyota
The conceptual foundation for kanban begins with Kiichiro Toyoda, who articulated the just-in-time concept in the 1930s — parts should arrive at each process just when needed, eliminating the waste of large inventories. But Kiichiro lacked a practical mechanism to execute this on the shop floor.
Taiichi Ohno solved this problem. In the late 1940s and early 1950s, Ohno was inspired by the American supermarket concept: a customer takes what they need from a shelf, and the store replenishes only what was taken. The downstream process (customer) pulls from the upstream process (shelf), and the act of removal is itself the signal to replenish.
Ohno began experimenting with kanban within his own machining operations at Toyota’s main plant. Critically, he did not roll it out company-wide immediately. The expansion from Ohno’s machine shop to all of Toyota’s internal operations and then to the supplier network took roughly two decades of deliberate, iterative development.
By the early 1960s, kanban was spreading from machining to assembly and other internal shops. Only after internal processes were stable did Toyota begin requiring first-tier suppliers to participate. Toyota’s 75-year history documents this as a slow, deliberate process — not a sudden implementation. By 1963, kanban was adopted at all Toyota plants.
How It Actually Works
There are two primary types of kanban at Toyota:
Production kanban (仕掛けかんばん / shikake kanban) — authorizes a process to produce a specific quantity of a specific part. When the downstream process withdraws parts, the production kanban returns upstream as authorization to make more.
Withdrawal kanban (引き取りかんばん / hikitori kanban) — authorizes the movement of parts from one location to another, such as from a parts supermarket to the assembly line, or from a supplier to the plant.
On Toyota’s floor: Parts sit in standardized containers. Each container has a kanban card specifying part number, quantity, source process, and destination. When assembly uses the parts, the card is detached and routed back. The upstream process collects returned cards and produces in the sequence and quantity indicated.
Ohno codified the rules:
- The downstream process withdraws from upstream only when needed (pull)
- The upstream process produces only what was withdrawn (no overproduction)
- Defective parts are never sent downstream
- The number of kanban should be minimized over time
- Kanban is used to adapt to small fluctuations in demand
Rule 4 is the improvement mechanism — reducing the number of kanban cards lowers the buffer between processes, which exposes problems that were previously hidden by inventory. This forces the organization to solve those problems, making the system progressively more capable.
Implementation Guidance
Kanban requires its prerequisites. Installing cards without the supporting system produces chaos, not flow.
Before implementing kanban, you need:
- Heijunka (leveled production) — without stable, leveled demand, kanban quantities fluctuate wildly and the system breaks down
- Stable processes — equipment must be reliable, changeovers must be fast, quality must be consistent
- Standardized work — cycle times must be stable for kanban quantities to be meaningful
- Small lot sizes — large batches defeat the purpose of pull; quick changeovers enable small lots
Start here:
- Begin between two processes you control, not across the whole value stream
- Use physical cards — the discipline of handling physical cards teaches the system’s logic
- Set initial kanban quantities conservatively, then reduce over time
- When problems surface (they will), solve them — don’t add kanban back to cover them up
- Extend to suppliers only after internal pull is stable
Common Mistakes
Implementing kanban without the prerequisites. This is the most common failure. Companies install kanban cards but skip heijunka, have unreliable equipment, and run large batches. The result is worse than the MRP system they replaced.
Confusing kanban with software “Kanban.” David Anderson’s Kanban method for software development borrowed the name but is a fundamentally different thing — a workflow visualization method. The manufacturing kanban is a production authorization signal, not a task board.
Thinking kanban eliminates inventory. Kanban controls inventory at defined levels. There is always some work-in-process in the system — the supermarket buffers are deliberate. The discipline is in capping and progressively reducing that inventory to expose problems.
Treating kanban as a standalone initiative. Ohno was explicit: kanban without the underlying production system disciplines is just a scheduling tool, and a poor one. It must be part of an integrated system including standardized work, jidoka, heijunka, and continuous improvement.
Adding kanban back when problems surface. When reducing kanban cards causes disruptions, the correct response is to solve the underlying problem (equipment reliability, changeover time, quality). Adding cards back is retreating from improvement.