Waving Strategies for Your Warehouse or DC
Wave picking is a warehouse order picking system where a worker will receive a picking list, and rather than walking back-and-forth, the items are grouped together by a common and specific order characteristics which can be zone, shipping priority, carrier, etc…The picker then collects the items for the order in a single, more optimized trip. “Waving” allows the distribution center management to leverage these characteristics which can help plan out labor, expected productivity goals, and workload across equipment. Digital orders are often time sensitive, which means wave planning can play a critical role in managing the order and workflow of the facility to get orders shipped on-time.
In this article we’ll look at possible waving strategies that will enable and support the demands of the new digital order processes.
Wave planning is a term for the process used in a warehouse management system (WMS) to support organizing the daily work flow based on order characteristics, labor and equipment constraints. Wave planning is applying short-interval-schedules (waves) that balances order characteristics and constraints to ensure orders and work to flow effectively through the distribution center. An important factor in wave planning is to enable order departure plans with the available labor. When the plan is satisfactory, it is accepted. Then the wave planners release the waves to the warehouse sequentially throughout the day, to allow managers to coordinate the several parallel and sequential activities required to complete the daily work.
The main goal of wave planning digital orders is to ensure the orders are processed efficiently while they meet their departure plans and ship to the customer on-time. Cut-off times are used in coordination with digital orders departure plans to ensure the wave of digital orders can be picked, packed and shipped on-time.
Digital vs. Wholesale Waves
In a distribution center where both wholesale orders are being processed with digital orders, wave planning can be the distinguishing factor. Web promotions may spike demand for a few items, these items can be batched in a wave to ensure picking efficiency. Because labor and equipment constraint can seriously affect the processing times of waves, the design of the facility should be such that flexibility of these constraints can be managed by wave planning. For example, where sortation equipment is being used to match batch picking with the outbound containers of an order, the sortation equipment may have to be design in such a way that a given number of shuts are assigned to digital orders and can be partitioned so two waves can be processed at the same time over the whole sorter. If this partitioning cannot happen, it might be better to send the digital orders to a put wall, so the digital orders are not waiting on the sorter.
Previously we have touched the concept of releasing waves, but because of its importance in managing digital orders we will approach the topic in more detail. The balancing act of managing wholesale and digital orders in the same facility comes down to how work is released to the floor. Wholesale waves can be large and demand a great deal of resources and suck the facility resources in such a way that digital waves may be shut down while waiting for the wholesale wave to complete. But if the facility is designed with some flexibility and extra capacity then resources can be assigned to just completing digital orders, and digital waves can be completed in parallel along with larger wholesale waves. For example, digital waves can be picked using discrete order or cluster picking concurrently as the wholesale waves are being picked. As pointed out above, batch picking can happen in parallel waves as long as the equipment can be partitioned or another order consolidation technique can be used.
The end of the wave planning process is to know exactly when to properly close the released waves. Waves can be delayed in being properly fulfilled; replenishments lingering, consolidation of orders being held up or equipment failure has stalled the wave. Closing the wave allows other waves to progress to use constrained resources. These resources, aka equipment must be cleared out of the old wave so the new wave can properly use that equipment. For digital orders, using continuous waving or waveless execution systems or partitioning shared equipment with wholesale waves can keep digital orders flowing through the facility to shipping.
Waves vs. Lean Time Order Release
Lean manufacturing has taught us principals like a ‘lot size of one’ and ‘excess capacity’ are preferred. These principals were examined closely by the manufacturing financial community and they were proven to be more important to meeting the customer needs versus some sub-optimal financial goals. The same is true for time sensitive orders in the distribution center, provide extra capacity so the customer delivery dates will be met. Thus, large waves may work for wholesale orders and even two or three-day lead time digital orders, but time sensitive digital orders where the customer is willing to pay for premium expedited freight need to be processed with more urgency. Such urgency may require digital orders be released as they are received, especially when the order is received with-in a certain time window close to the carrier pick-up time. The emerging execution technology calls this ‘continuous waving’ or ‘waveless’. The warehouse execution system (control system) is handling the release of work to the distribution center to flatten the peak and valleys of work produced by “classic WMS waving”.
Is your operation currently performing wave picking? Drop us a line and let’s talk wave planning strategy!
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