8  Replenishment in Practice

Keywords

Replenishment, Warehouse Management System, Pick Face, Storage Optimization, Inventory Management

8.1 What is Replenishment?

• Process of ensuring the right products and quantities are in the correct pick location at all times (Richards 2018).
  • Empty pick slot = lost sale
  • Poor replenishment = order shortages, increased picking times, increased cost per pick, reduced service level

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8.2 When to Replenish?

• Real-time WMS can recognize need to replenish through real-time data transfer. Strategies include:
  • Identify total actual order quantities and replenish before next wave of orders arrive
  • Trigger when stock level within pick face falls to a certain level
• Timing is crucial:
  • Early replenishment can lead to overfull pick faces and FIFO issues
  • Late replenishment can occur if staff pick out of sequence

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8.3 How to Replenish?

• Move product directly to pick face from inbound section to cut out processes
  • Requires pre-planning to avoid overfilling pick faces
  • Pallets can be de-layered to correspond with expected pick quantities
• In absence of real-time WMS:
  • Design pick faces to take optimum quantity based on predicted sales per day/shift and cubic capacity
  • Train staff to identify replenishment needs and inform supervisor or forklift driver

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8.4 Example: A Heat-Map for Replenishment

• In the fashion industry, clothing racking systems are used to store hanging garments on beams or tubes to prevent wrinkling or damage.
• Commonly, tiered picking shelves with mezzanines and walkways (pick modules) are installed to maximize storage capacity while providing direct access to goods.
• Restocking is often done chaotically, with items placed in any available location.
• A heat-map can visualize storage locations based on inventory levels, helping employees find empty spots for replenishment.

Example of clothing racking storage system by Mecalux (2023).

“In fashion retail, there are two ways to store clothes: in boxes or on hangers. Boxes are used to hold clothing that’s folded and bagged. They can be stored in any system that facilitates their handling and picking, i.e., picking shelves or automated storage and retrieval systems (AS/RS) for boxes. Unlike folded clothes, hanging garments require an adapted solution to keep them in an upright position to prevent wrinkling or damage.
Warehouse clothing racking are specific solutions that offer direct access to goods and whose structure can be adapted to store garments on several tiers. Hangers can be placed:
On beams: hanging garments are suspended from the racking beams. If your company manages high-turnover products, you can install two side-by-side racking units to optimise storage space and maintain direct access to the goods.
On tubes: a tube (or two, depending on warehouse needs) is attached between two racking frames.
In the garment industry, businesses typically install storage solutions that provide the highest possible capacity. One of the most popular options is tiered picking shelves with mezzanines and walkways, i.e., pick modules. This is because they multiply the storage capacity by the number of levels configured while providing direct access to the goods.” (Mecalux) (snapshot)

8.5 Picking vs. Replenishment

• Simultaneous picking and replenishment can:
  • Cause safety issues if forklifts and pedestrian pickers work in the same aisle.
  • Lead to confusion if both are at a location at the same time.
• Solutions include:
  • Incorporating multiple picking locations for the same SKU
  • Using storage handling systems that better separate the picking and replenishment processes (e.g., A frames, carton live storage, or flow racking)
  • Carrying out the two activities at different times of the day if feasible.

Carton flow racking uses inclined platforms with rollers, separating storage and picking aisles to reduce congestion and improve workflow (Mecalux 2025).

“Replenishment In order to ensure a smooth and efficient picking process we need to ensure that the right products and quantities are in the correct pick location at all times. This is replenishment. As in the case of replenishing overall inventory to ensure customer satisfaction, the warehouse also has to replenish its pick faces regularly to ensure picker satisfaction. An empty picking slot, just like an empty shelf location in store can mean a lost sale. The result of a poor replenishment process is order shortages, increased picking times and therefore increased cost per pick and an overall reduction in service level. Real-time WMSs will recognize the need to replenish pick locations through real-time data transfer. These systems are also able to identify the total actual order quantities and therefore replenish before the next wave of orders arrive on the warehouse floor. Other systems will rely on a trigger that denotes when the stock level within a pick face falls to a certain level. This will rely heavily on timing as orders that have generated pick lists may not actually have been picked and therefore replenishment has been triggered early. Late replenishment can result where staff have picked out of sequence, for example, and emptied the pick bays before the replenishment team have had an opportunity to top up the location. Timing is crucial. An early instruction to replenish can cause as many problems as late replenishment, with potentially overfull pick faces and issues with FIFO. If product can be moved directly to the pick face from the inbound section this cuts out a number of processes. This will require a certain amount of pre-planning to ensure that pick faces are not overfilled. Pallets can be de-layered to correspond with expected pick quantities. In the absence of a real time warehouse management system the warehouse manager will need to first ensure that the pick faces are designed to take the optimum quantity of product based on predicted sales per day or per shift, cubic capacity of the pick location, and staff need to be trained to identify replenishment requirements and inform either the supervisor or the forklift truck driver, depending on how the process has been set up. One other point to note here is that although real time dictates that replenishment and picking can occur simultaneously, there are issues of worker safety if forklift trucks and pedestrian pickers are working together in the same aisle. It can also lead to confusion if both are at a location at the same time. This can be alleviated by incorporating multiple picking locations for the same SKU, the utilization of A frames, carton live storage or flow racking where product is replenished from a separate aisle. The two activities can also be carried out at different times of the day if feasible. For example, receiving and replenishment can take place in the morning whilst picking takes place in the afternoon. Carousels and areas where forklift trucks are in constant use must be replenished at different times to avoid slowing down the operation and endangering staff. Alternatively, replenishment can take place during breaks or after picking has been completed for the day. This mirrors what happens at retail stores where shelf replenishment takes place when stores are closed overnight.” (Richards, 2018, p. 299) (pdf)

8.6 References

Mecalux. 2023. “Warehouse Clothing Racking: How to Store Garments.” Supply Chain & Warehouse Logistics Blog. January 26, 2023. https://www.mecalux.com/blog/warehouse-clothing-racking.

Mecalux. 2025. “Live Storage for Picking.” Mecalux. 2025. https://www.mecalux.com/picking/live-storage-for-picking.

Richards, Gwynne. 2018. Warehouse Management: A Complete Guide to Improving Efficiency and Minimizing Costs in the Modern Warehouse. 3rd Edition. New York: Kogan Page Ltd.