Pros and Cons of Wave Picking

One of the most time- and labor-intensive tasks completed in any order fulfillment operation is order picking—the act of picking the individual components and inventory that make up an order. Order picking can be fully manual, partially automated, or even fully automated, depending on the type of product being picked and the individual needs of the business.

When picking is partially or fully manual, there are a number of different picking strategies, techniques, or methodologies that can be used, each of which has its own potential benefits and drawbacks, and each of which is better suited for fulfilling different requirements.

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One common picking strategy is known as wave picking. Below, we define wave picking and explore how it works, discuss the pros and cons of leveraging it in your operation, and take a look at some alternative strategies you may want to consider.

What is Wave Picking?

Wave picking is a picking strategy that can be considered a variation of zone picking and batch picking.

It essentially works by grouping orders into a batch (or “wave”). At the beginning of a wave, the picker receives their pick assignments for the wave either digitally or in a pick list, and works through their zone picking what is required. The goods that have been picked are then forwarded through sortation and consolidation into discrete orders and, ultimately, prepared for shipping. All batches within a given pick module that are a part of the wave must be completed before the next wave can begin.

It is important to note that in wave picking, batches are static. This means that once the wave has begun, the batches will not change.

The main benefit of wave picking is the fact that it gives pickers a large workload as they complete a single pass-through in the pick module. Then, the next wave typically starts at where the picker finished with the picker working this wave in the opposite direction minimizing travel time. This can make wave picking a good strategy for operations that receive high-volume orders multiple times per day; for example, a business-to-business setting.

The primary disadvantage of wave picking is that most waves will have an anomaly of some sort—a mislabeled carton, a short-pick, a mis-pick, etc.—that will require reconciliation. While you are reconciling the orders, it’s a challenge to run the next order into the truck, because the next wave essentially buries the first wave. This means that the next wave may need to be paused during the reconciliation process.

Typically, the larger the wave, the more efficient it is for the pickers because they are getting more work done for each step that they take. That being said, the larger the wave, the greater the risk of some sort of mis-pick or other error that will require reconciliation. On the other hand, the smaller the wave, the simpler it will typically be, and the lower the risk of an error that requires reconciliation. The challenge for operations leveraging a wave picking strategy is to balance a desire for large waves with the need for few errors.

Another potential drawback to wave picking is the fact that the work being done is not consistent throughout the day. Periods of low activity and low throughput are sandwiched between waves, due in part to the reconciliation process.

Alternatives to Wave Picking

There are two primary alternatives to wave picking: Waveless and overlapping waves.

Waveless picking was developed in as an alternative to wave picking with an eye toward ecommerce applications, where same-day and next-day shipping have become increasingly important. In waveless picking, orders are constantly added into the batch as previous orders are completed. This means that batches are dynamic; they are constantly changing. As a picker completes one pick, the WES automatically checks to see what the next best pick is for them to complete, and routes them to the next optimal spot. Waveless picking often levels out the peaks and valleys in productivity, but it limits the number of picks available to the picker which can increase travel time and lower picking efficiency.

Overlapping waves, on the other hand, involves allowing one wave to reach its peak before releasing the next wave. As the first wave begins to become less productive (typically toward the end of the wave), the WES introduces the second wave, allowing them to “overlap.” Overlapping waves in this manner keeps the entire system working at a higher rate of productivity compared to wave picking. This results in more level productivity, as in waveless picking, but with a much higher total throughput.

Which Strategy is Right for You?

It’s important to note that none of these strategies is inherently better than the others. The right strategy for your operation will be dictated by the unique circumstances of your business: The type of orders you receive and fulfill, the type of product you handle, your throughput and level or automation, etc.

It’s also important to note that it is possible to find yourself in a situation where one strategy no longer makes sense for your operation. For example, a business that originally catered to large B2B orders would likely have leveraged wave picking. If the business shifts to fulfilling smaller B2C orders, then wave picking might not make sense anymore. With this in mind, it is important to ensure that you are utilizing a WES that can change and adapt alongside your business—for example, one capable of executing wave, waveless, or overlapping waves.

If you are unsure of the picking strategy that is best for you, speaking with a trusted systems integrator can help you understand your options and the technology, software, and equipment that you’ll need to make it happen. Contact us today to speak with a member of the Conveyco Team.