A Kanban System uses visual signals to trigger replenishment or production based on actual consumption, helping control flow, inventory, and response.
Definition
A Kanban System is a pull-control method that uses cards, containers, boards, electronic signals, or other visual cues to authorize production or replenishment. The signal is triggered by actual consumption rather than forecast push.
Kanban helps limit work-in-process, expose problems, reduce overproduction, and connect processes with simple replenishment rules.
History
Kanban is a core Toyota Production System practice inspired partly by supermarket replenishment: replace what the customer has taken. It became one of the most recognizable Lean tools because it makes flow and inventory control visible.
Kanban later spread into service, software, healthcare, and knowledge work as a way to visualize work, limit WIP, and manage flow.
When to Use
Use Kanban when demand is recurring, replenishment can be standardized, items can be visually controlled, and upstream processes can respond reliably. It works for parts, supplies, paperwork, digital tasks, and service queues.
Do not use Kanban to hide unstable processes. If quality, supplier reliability, or lead time is highly erratic, stabilize or size buffers carefully first.
Step-by-Step
- Define item, customer, supplier, and replenishment loop.
- Measure demand, lead time, container quantity, and variation.
- Set kanban quantity and trigger rules.
- Create visual signals and standard locations.
- Define maximum WIP and abnormal conditions.
- Train users on pull rules and no-expedite discipline.
- Monitor shortages, excess inventory, aging, and signal accuracy.
- Adjust quantities as demand and lead time change.
Examples
- Production: Empty containers trigger replenishment from upstream machining.
- Maintenance: Two-bin parts system triggers reorder when the first bin is empty.
- Healthcare: Visual cards trigger restock of clinical supplies.
- Office: A kanban board limits active improvement work.
Common Pitfalls
- Using kanban without stable replenishment lead time.
- Too many cards or oversized containers.
- Ignoring demand changes.
- Allowing hidden side inventory.
- No response rule for missing cards or stockouts.
- Treating kanban as only labels, not a pull system.