Kanban Card
Is a kanban card an order or just a signal?
It is both a signal and an authorization mechanism: it communicates that replenishment is needed and authorizes the next action, whether that is production, transfer, or purchase.
What makes kanban different from normal inventory reordering?
Kanban is consumption-triggered and container-based, while conventional reorder systems are often forecast- or review-driven. Kanban links replenishment directly to actual use at the point of consumption.
What is the biggest operational risk if kanban is used without process discipline?
The system becomes unreliable if cards are not returned immediately, if containers are mixed, or if lead times change without recalculating card quantity, because the visual signal no longer matches actual consumption and replenishment timing.
A kanban card is a visual replenishment signal used in lean manufacturing and inventory control to authorize production, movement, or purchase only when downstream consumption creates a need. Attached to a standard container or bin, the card is removed when the container is emptied and sent upstream to trigger replenishment, carrying key data such as part number, quantity, and source and destination locations. It is a core element of a pull system rather than push scheduling.
On the shop floor, a kanban card prevents overproduction by ensuring an upstream process only makes parts when a downstream process has consumed them, which supports just-in-time flow and limits work-in-process inventory. In warehousing, a card attached to a bin or rack signals the warehouse to refill a supermarket location or staging area, keeping the right quantity at the point of use and reducing search time, waiting, and excess handling. For raw material tracking, the card acts as the control token tying inventory to a specific container and replenishment chain. Oracle describes pull sequences as the replenishment chains between point of supply and point of use, with kanban cards used as visual signals to replenish materials in standard containers or bins. Cards can be physical or digital and support production, transfer, and supplier kanban flows. The card also defines replenishment loop size: if a work center must have 100 units available and kanban size is 20, five cards are needed, directly converting demand coverage into controlled inventory signals.
Card loss or mismatch at point of use: when a card is detached, misfiled, or assigned to the wrong container, replenishment is not triggered correctly, causing a stockout at the workstation or the wrong item being refilled. This breaks the pull signal and disrupts flow.
Incorrect kanban sizing: if the card quantity or number of cards is set too low relative to demand and replenishment lead time, the line can starve; if set too high, the system accumulates excess inventory and WIP, defeating lean control. Sizing errors directly create shortages or surplus.
Weak receiving and replenishment discipline in warehousing: if inbound material is not promptly processed when a supplier kanban is triggered, the downstream bin empties before replacement arrives, creating a bottleneck at receiving or staging. The result is missed takt, line stoppage, and emergency expediting.