Wave Pick and Load
in Warehouse Management Systems

by Don Benson


Early in my consulting career, I had the good fortune to work for a firm that made a significant contribution to the development and implementation of Warehouse Management Systems. At that time, there were few vendors, and the pricing was much higher than most of our clients could afford. Consequently, much of our work was to support the development of customized warehouse management systems to support new warehouse operation. In that role, our unique contribution to warehouse management systems was the creation of the functionality we called “wave pick and load” (WPL).  Our intent with WPL was to enable managers to organize their daily workload and to create and sustain a consistent flow of materials through the warehouse. Except for our clients’ specifications, we did not document this work. We had no idea what would happen in the future with what we had created.

Recently, after some years away from that work, I was asked to help with several WMS projects involving distribution centers that were not achieving their desired outcomes. Interestingly, I found that the definition, understanding, and use of wave pick and load had changed, in much the same way that words change in the children’s game of Telephone.

Most WMS products now provide wave planning support to help managers organize their work, although I find it not well documented by the vendors or in the press. I have also found that many products now use wave picking to describe the ability of a WMS to combine multiple orders within a wave for “batch picking,” which can significantly reduce the number of trips through a pick path or to direct “goods to picker” systems. And others have published articles suggesting that warehouse operations no longer need wave functionality, although they do not specify what aspects of warehouse operation or of WPL functionality are no longer needed.

In this article, I'll explain our initial intent with wave pick and load—to support warehouse management—and the methods and procedures that subsequently were developed to increase the value of a WMS in the utilization of warehouse resources.

Wave Pick and Load in a WMS

Warehouse management systems were created to compensate for deficiencies in business systems, and for warehouse managers to improve throughput and the quality of operational performance. The first of the features was a locator system which was used to record the placement of merchandise and create a location-sequenced picking document. Over time, these systems added functionality to help managers better use their resources in handling the growing and dynamically changing daily requirements presented to the warehouse by company management and their customers. These requirements include sales, inventory, SKUs, channels of distribution (including those created by new technologies like e-commerce), and competition from retailer to manufacturer.

Our interest in organizing grew out of our understanding of the functions of management. In previous articles, I have described how we applied each of the functions—planning, organizing, staffing, directing, and controlling—to warehouse operations. Our understanding was that once a daily plan had been developed, specifically identifying the orders to be picked and shipped and the scheduling of carrier departures from the dock, or a target throughput established (e-commerce), the wave pick and load function would organize the work for the subsequent management and staff tasks that follow.
Our objective with WPL was to organize the flow of materials through the warehouse to best use the resources to accomplish the plan. WPL organization typically:

⦁    Provides a template for planners to organize the sequence in which orders will be picked and loaded onto shipping vehicles based on sequence of route delivery, or scheduled vehicle departure time, or customer requested speed of delivery, etc.

⦁    Has the planner then assign the orders into four to eight short interval periods (waves), based on the sequence of the vehicle departure plan, and place a similarly sized workload in each wave. Typically each wave would include all of an order, and would be assigned a specific staging area destination on the shipping dock for order assembly.

⦁    Provides with the wave structure:

⦁    An estimate of the staffing required by work area, enabling supervisors to direct their staffing and coordinate the work by work area

⦁    Milestone points, at the end of each wave, to monitor and control performance by work area, providing supervisors the opportunity to reallocate staff to keep the flow of all work areas synchronized throughout the day

Wave planning enables the WMS to use its database to improve labor productivity and optimize the use of warehouse space and equipment by sequencing activities by wave.

1. To improve picking productivity and throughput, the WMS can unbundle orders to:

⦁    Direct simultaneous picking of the repack, case, pallets, and other portions of orders in separate work areas.

⦁    Support a variety of picking methods (order and batch) repack and cases.

⦁    Manage mechanized handling including dispensers, pick and put to light, conveyors and sortation, robots, ASRS, carousels, batch carts, etc.

⦁    Communicate pick instructions to direct picking process with data, lights and voice.

⦁    Direct the sortation of batch-picked, less-than-case quantities into cartons or totes by order

⦁    Facilitate the assembly of portions into completed orders on the shipping dock with bar code scanning and other auto ID technologies.

2. Improve picking productivity by reducing the travel time (pick path) by allowing the layout to include appropriately-sized forward positions for picking repack and full-case quantities.

3. Improve throughput by directing materials/merchandise replenishment to forward pick positions to ensure adequate quantities will be in the pick positions prior to the time when pickers are scheduled to arrive (typically in the prior wave).

4. Improve labor productivity and minimize the length of the pick path, by scheduling the removal of empty pallets from case pick locations.

5. Capture and record transaction data with which to:

⦁    Measure actual productivity and performance throughout the day by work area, by wave.

⦁    Improve estimates of staffing requirements.

⦁    Create and maintain a baseline for setting department goals, discussing process changes (Lean, TQM, etc.), and budgeting.

⦁    Compare productivity results with other work shifts, other companies, and across industries.

⦁    Provide daily feedback to the staff about their performance as a team.

⦁    Better understand the nature of the work, and how it changes seasonally as a consequence of changes in demand, sales efforts, and marketing campaigns.

If you consider purchasing a WMS, or reviewing how you are using a WMS, I recommend you explore the ways in which the application of wave planning could support your warehouse.  Organizing the workload in waves provides a powerful foundation for implementing processes that can build the capability and improve the productivity of your warehouse operation.

Don Benson, also known as The Warehouse Coach, is a systems thinker, bringing ideas, people and organizations together to achieve their desired outcomes with Warehouse Management Systems for over 35 years.  You can reach him at www.wmssupport.com.

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