Why Picking Stops When You Are Not Out of Stock
The WMS says there are 300 units on hand, yet the picker is standing in front of an empty slot. The stock exists, but it is sitting on a pallet in upper reserve racking, not in the pick face within arm's reach. This is an in-warehouse stockout.
The emergency replenishment that follows is expensive. A forklift abandons its putaway task and enters the pick aisle, which stops picking in that aisle too. The picker skips the item and has to come back later, so the whole order finishes late. The goal of replenishment logic is to fill the pick face before any of this happens.
Four Replenishment Methods and When to Use Them
In practice, no warehouse runs on one method. Combine them by velocity class: fast movers get min-max with demand-based layered on top, while slow movers can run on scheduled replenishment alone.
Sizing the Pick Face and Setting Trigger Quantities
The starting point for the minimum is the quantity shipped during replenishment lead time. The pick face has to last from the moment a task is created until product is physically placed in the slot.
Take an item with daily shipments of 120 units, an 8-hour working day, and a 2-hour replenishment lead time:
The average suggests 30 units, but once you account for the busiest hours, the minimum should be at least 60. The maximum is set by the physical capacity of the pick face and how often you want to replenish. With a maximum of 180, each replenishment moves about 120 units, which works out to roughly one replenishment a day.
Oversize the pick face and a handful of items occupy the golden zone, stretching pick paths. Undersize it and replenishment frequency climbs, adding forklift workload and aisle congestion. Finding that balance from per-item daily shipment data is the core of replenishment design.
Scheduling Replenishment So It Does Not Collide with Picking
Replenishment tasks need priorities. A common order is emergency > demand-based > min-max > scheduled, with tasks tied to orders nearest their shipping cutoff moved to the front.
Task interleaving also pays off. When a forklift has put away an inbound pallet and is returning with empty forks, assigning it a replenishment task from a nearby reserve location cuts empty travel.
Timing matters as well. Before releasing a wave, calculate its requirements and complete pre-wave replenishment first. Then push min-max replenishment into off-peak windows such as lunch breaks or shift changes, so forklifts and pickers meet in the aisle less often.
Expiry Dates, Lots, and Replenishment
Choosing the source location purely by proximity breaks stock rotation. For date-controlled items, the source should be the lot with the earliest expiry (FEFO), and a lot that expires earlier than what is already in the pick face should never arrive after it.
Metrics That Show Whether Replenishment Is Working
Review all three weekly and build a routine for adjusting min-max quantities, so your settings do not fall behind seasonality or assortment changes.
How POLYGLOTSOFT WMS Supports Replenishment Design
POLYGLOTSOFT analyzes shipment history to derive velocity classes and peak patterns for each item, then uses them to set pick-face capacity and min-max quantities. We implement demand-based replenishment, pre-wave replenishment, task interleaving, and FEFO-based source selection as WMS logic tailored to how your warehouse operates. If pick-face stockouts are delaying your shipments, contact POLYGLOTSOFT.