Signal Kanban
What is the main difference between signal kanban and a regular withdrawal kanban?
A regular kanban authorizes movement or withdrawal for each container, while a signal kanban authorizes the start of a batch when a threshold or reorder point is reached.
When is signal kanban a better fit than one-piece-flow kanban?
It fits best when setup time is long, lot sizes are fixed, or the item is consumed from a single buffer and replenished in batches rather than individual containers.
Can signal kanban be electronic?
Yes; some systems allow a scanned or electronically generated replenishment signal, although implementations differ and some legacy approaches emphasize visual/manual signaling.
A signal kanban is a single-card or single-trigger kanban that authorizes batch replenishment or production when inventory reaches a defined reorder point, rather than when each container empties. It is used in large-batch situations with costly changeovers and signals the next production lot from a fixed buffer or storage location in a pull system.
On the shop floor, signal kanban governs replenishment for parts with predictable demand and high setup costs. Instead of managing every bin, operators watch one designated trigger point—a card, tank level, pallet count, or container count—placed at the reorder level. When consumption drops stock to that point, the signal releases a fixed-size production lot or supplier order. This works well in bulk materials, tanks, and high-volume components, where frequent changeovers are impractical. In a warehouse supermarket, the signal is tied to the reorder point so a new batch is ordered only after actual usage reaches the threshold. In ERP/MES environments, scanning the signal can update container status and automatically create replenishment elements or goods receipts. Because only one item carries the signal, physical handling is simple, but transparency is lower; some organizations adopt an extended signal kanban variant for better visibility.
Late signal release: If the reorder point is set too low or scanning discipline slips, the upstream process starts late and downstream lines run dry before the batch arrives. The result is an avoidable stockout and expedited firefighting.
Batch overproduction: When lot sizes or lead-time assumptions are wrong, the triggered batch creates overproduction and congestion. Downstream waits while the upstream machine finishes the lot, so material flow stalls and WIP builds.
Missed trigger signal: If the card is lost, misread, or never captured, replenishment stalls with no obvious alert. Empty supermarket slots, bottlenecked receiving, and untracked WIP follow before anyone notices.