Using Put Walls to Flex the Warehouse for the Holiday Surge

The weather is balmy, and many of us are thinking about the beach or the lakes. But, from a planning perspective, the holiday season isn’t that far away. With the holidays comes an increase in commercial activity, and it’s not too soon to think about effective ways to handle the increase in fulfillment volume. During the holiday surge, it is imperative that a warehouse be able to flex to handle the increasing volume of work. And one key process increasingly used to accomplish this is the use of “put walls.” Put walls are a cost effective way to assemble multi-line orders for e-fulfillment.

In a put wall, a warehouse management system (WMS) disaggregates the order lines from different customer orders. So, for example, if 6 customers order the same item (SKU 123), then those six SKU 123 items are picked at the same time and put into the same tote.  The tote is then generally placed on a conveyor, and routed to the put wall. The put wall looks like a shoe cubby with the cubby being open in both the front and rear. The 6 items of SKU 123 are then placed into six separate cubby totes in six separate cubbies. Each cubby represents a location for order assembly for a particular customer. On the other side of the put wall, a worker takes a tote out of the wall when an order has all the line items necessary to complete it. The goods are then packaged and routed to shipping.

That is the basic process. But Mike Khodl, the Vice President of Solution Development at Dematic, walked me through several variations off of this process.

The upstream batch picking can be automated, the use of multi-shuttles for automated storage and retrieval; or more manual, workers may walk through the warehouse and fill up a cart that holds several totes.

Totes may be designed to hold just one SKU. Or totes may have colored dividers, so SKU 123 will be in the orange slot in a tote, and SKU 789 might be in the green slot in the same tote.

Products may have “AB labels” on the corner so that the items can be uniformly oriented within a tote or tote compartment. This makes the job for the downstream person at the put wall easier. Or products can lack these orientation labels.

At the put wall, puts (and pulls on the other side of the wall) may occur based upon put-to-light or based on a voice system. Lights are more common than voice. The lights can be one color or multiple colors. When multiple colors are used one worker may only be putting into slots that light up red, while a different worker is putting to slots that light up green. Workers may wear a ring scanner for an extra scan, an extra accuracy check, before putting the goods into the wall slots.

The put walls can be a flat wall, or may have “L” or “U” shaped layouts to better maximize space. Further, these put walls can be mobile – they can be on casters; hidden in a back corner of the facility under tarps and only rolled out for peak volumes.

If a warehouse makes use of the put wall all year long, during most of the year you may have one person working a section of the wall that does puts for a while, then moves to the other side and does packaging. During the holiday surge season, you may need several people per section on both sides of the wall.

With all the variations off this process, it is easy to see why hiring a consulting firm that has done time motion studies surrounding the different process variations, could be a sensible course of action.

One complaint about put walls is that they violate lean principals by requiring extra touches. But both Mike’s and my perspective is that if you have RF scans in place to insure the perfect order, and you have  a process that delivers higher throughput at a lower cost, then so what?

Finally, what I like most about put walls is that this is a process that can handle holiday surge volumes at a relatively low cost.

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