What is a kanban system in manufacturing?

A kanban system is a pull-based production control method that uses visual signals (cards, bins, or electronic alerts) to trigger replenishment only when downstream processes consume material. This prevents overproduction and reduces work-in-process inventory.

How do you calculate kanban quantity?

Kanban quantity = (Daily demand × Lead time × Safety factor) ÷ Container size. The safety factor (typically 1.2-1.5) accounts for variability. Start with more kanban cards and reduce over time as processes stabilize.

What is the difference between kanban and just-in-time?

Just-in-time (JIT) is the broader philosophy of producing only what is needed, when needed, in the quantity needed. Kanban is the signaling mechanism that implements JIT on the shop floor by controlling when production and material movement occur.

Kanban Systems in Manufacturing

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We recommend reading these guides first to get the most out of this one:

Lean Manufacturing Push vs Pull Systems

Pull

Not Push

Kanban Rules

Visual

Signal to Produce

WIP Cap

Limits Overproduction

What Is Kanban?

Kanban (Japanese for "visual signal") is a scheduling system that controls production and inventory by using visual signals to trigger replenishment based on actual consumption. Instead of producing to a forecast (push), kanban produces to actual demand (pull).

The simplest kanban: an empty bin. When a downstream process empties a bin of parts, the empty bin is sent back upstream as a signal to produce more. No schedule, no forecast, no MRP run — just a visual signal tied to real consumption.

Kanban Is Not a Board on a Wall

In software development, "kanban" often means a task board with columns. In manufacturing, kanban is a production control system — physical signals (cards, bins, empty spaces) that limit WIP and trigger replenishment. The software board borrowed the name, but the original is a supply chain mechanism.

Types of Kanban Systems

Type	How It Works	Best For
Two-Bin System	Two containers of parts. Use from Bin A. When empty, switch to Bin B and send Bin A for refill.	Simple, high-volume, small parts (fasteners, consumables)
Card Kanban	Physical cards attached to containers. Card returns upstream when container is consumed, triggering production.	Production cells, assembly lines, multi-part systems
Signal Kanban	A single card that triggers a batch production run when inventory hits a reorder point.	Batch processes (stamping, injection molding) with long changeovers
Floor Space Kanban	Marked squares on the floor. When the square is empty, produce. When full, stop.	Large items (pallets, assemblies, bulky components)
Electronic Kanban (e-Kanban)	Digital signals triggered by barcode scans or sensor-based consumption tracking.	Multi-site, high-volume, ERP-integrated environments

The 6 Rules of Kanban

Toyota established six rules that make kanban work. Break any of these and the system collapses:

Do not send defective products downstreamQuality at the source is non-negotiable. If you send defects forward, the downstream process stops — and the kanban signal lies about what was actually consumed. See poka-yoke.

The downstream process withdraws only what is neededNo cherry-picking, no hoarding, no "just in case" extra pulls. Take exactly the quantity on the kanban card, at the time needed.

Produce only the quantity withdrawn by downstreamNo overproduction. If the kanban card says 50, produce 50 — not 60 "just to be safe." Overproduction is the worst waste.

Level the production loadKanban works best with stable, level demand. Wild demand swings break the system. Use heijunka to smooth the schedule.

Kanban is a tool for fine-tuningKanban maintains the current state. Kaizen improves the state. Reduce the number of kanban cards over time to expose problems and drive improvement.

Stabilize and rationalize the processKanban requires reliable processes. If your machines break down randomly, changeovers are unpredictable, or quality is inconsistent, fix those first with TPM and standard work.

Sizing a Kanban

The number of kanban cards (or containers) determines the maximum WIP in the system. Too many cards = excess inventory. Too few = starvation and stockouts.

Kanban Quantity Formula

Number of Kanbans = (Daily Demand × Lead Time × Safety Factor) ÷ Container Size

Where lead time includes production time + transport time + waiting time, and safety factor is typically 1.1-1.5 depending on process reliability. As you improve the process, reduce the safety factor and remove cards.

Implementing Kanban

Start with One LoopPick one product family between two processes. Do not try to kanban the entire plant at once. Learn on a small scale.

Stabilize the Process FirstKanban exposes problems ruthlessly. If your process is not stable (equipment reliability, standard work, quality), fix that first or kanban will just create chaos.

Calculate and Set Initial QuantitiesUse the formula above. Start with slightly more kanbans than you think you need. It is easier to remove cards than to recover from starvation.

Make It VisualKanban boards, colored bins, marked floor spaces. Everyone should be able to see the status of every loop at a glance. See visual management.

Reduce Cards Over TimePeriodically remove one kanban card. This lowers WIP and exposes the next problem. Fix the problem, stabilize, then remove another card. This is kanban-driven kaizen.

✅ Kanban Success

Process is stable before kanban is implemented
Rules are followed without exception
Cards are reduced over time to drive improvement
Visual signals are clear and self-explanatory

❌ Kanban Failure

Implemented on an unstable process
People override signals ("just in case" production)
Number of cards never changes after initial setup
Cards get lost, damaged, or ignored

🎯 Key Takeaway

Kanban is the simplest and most powerful tool for controlling WIP and connecting production to real demand. But it only works when the six rules are followed and the underlying process is stable. Start with one loop, make it visual, follow the rules, and then gradually reduce cards to expose and solve problems. That is lean at its purest: use the system to drive improvement.