What Kanban is
Kanban means "visual card" in Japanese. It's the mechanism that makes pull production possible inside the Toyota Production System: instead of pushing parts based on a demand forecast, each process only produces once it receives a signal — a card, an empty bin, an electronic signal — that the downstream process has actually consumed material.
Types of Kanban card
Production Kanban
Authorizes a process to manufacture a specific quantity of an item.
Withdrawal (Transport) Kanban
Authorizes moving a batch of parts from an intermediate stock to the next process.
Supplier Kanban
Triggers raw-material replenishment from an external supplier based on actual consumption.
How it works in practice
Every container of parts has an associated Kanban card. When the container empties, the card returns to the upstream process as a replenishment order. That cycle naturally caps work-in-process (WIP) inventory, since a kanban only exists to replace what's actually been consumed — eliminating overproduction.
Kanban isn't an inventory-control tool, it's an overproduction limiter disguised as a card.
How to calculate the number of cards
A simple sizing formula is:
Number of cards = (Daily demand × Replenishment lead time × Safety factor) ÷ Quantity per container
The more stable the demand and the shorter the replenishment lead time, the fewer cards — and less inventory — the system needs to run without breaking. Gradually removing cards is a classic technique for forcing continuous improvement: fewer cards exposes the bottlenecks that inventory was hiding.
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About the author
Lean Manufacturing & Behavioral Management Specialist
Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.