Replenishment Signal
A replenishment signal is the event or trigger that tells a system or operator that material must be restocked, moved, or produced to restore inventory at a point of use or storage location. In Kanban manufacturing, it can be manual, electronic, or automatic, often fired by scanning a card, returning an empty container, or crossing a reorder-point threshold.
On the shop floor, a replenishment signal keeps line-side bins, supermarket locations, and WIP buffers fed without overstocking. It represents a container's worth of material and is generated when a card is scanned, an empty bin is returned, or a reorder-point rule detects on-hand plus WIP within lead time below threshold. In warehouse execution, the signal becomes a replenishment task moving stock from reserve to pick-face, from an internal subinventory to another location, or from an external supplier to the plant, with priority, source, destination, and quantity. To be executable, it needs a defined source, lot size or container quantity, and a control rule like minimum/maximum, reorder point, or Kanban card count. Consumption-driven signals fire close to actual use, arming MES, ERP, or WMS workflows that timestamp the trigger and route transport, supplier delivery, or pick-face refill tasks while preserving FIFO and container-level accuracy.
- Late or missed signal: If scanning discipline is weak or bins are not returned promptly, the signal fires after the line has already consumed the last usable quantity, causing line-side stockout, expedites, and operator waiting time.
- Wrong trigger logic: If reorder point, lead time, or WIP assumptions are wrong, the system may trigger too early or too late, leaving excess inventory clogging receiving and storage or shortages that appear despite green system status.
- Container/lot mismatch: If the replenishment signal is configured for the wrong Kanban container size or lot size, the system rounds to an incorrect quantity, creating partial fills, excess transport moves, or shortages not cleared by one replenishment task.
Is a replenishment signal the same as a purchase order?
No. A replenishment signal is the trigger that initiates the restocking event, while the purchase order, transfer task, Kanban card action, or production order is the execution response. The signal tells the system that material is needed; the execution document tells the system how to provide it.
What inputs determine whether a replenishment signal fires?
Common inputs are on-hand quantity, WIP within lead time, reorder point or minimum threshold, Kanban container count, lot size, and replenishment source availability. The logic compares live inventory position against these thresholds or counts to decide when a signal is needed.
Can replenishment signals be used for internal movements as well as supplier replenishment?
Yes. Replenishment can come from external suppliers, internal subinventories or locators, work orders, or other organizations. The resulting action may be a transport task moving reserve stock to pick-face or a replenishment request sent to the supplier.