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Focus: Distribution/Materials Handling

Feature Article from Our Distribution and Materials Handling Subject Area - See All

From SCDigest's On-Target E-Magazine

-Feb. 11, 2014 -

Logistics News: Automating Split Case Picking Movement can Deliver Productivity Gains in eFulfillment, Store-Level Replenishment, More

Systems First Implemented in Late 1990s to Intelligently Move Cartons to Right Pick Zones Commonplace Now, but Still Under Deployed


 SCDigest Editorial Staff

The amount of "split case" order picking, sometimes also called "eaches picking," is in general thought to be on the rise.

The reasons? One is certainly that major retailers such as Walmart are looking for vendors to help them reduce the retailer's own logistics costs by picking and shipping for each individual store. Those store-specific cartons are then crossdocked after shipment to the retail DC, eliminating the need for the retailer to take in full cartons and do its own store-level picking in its DC.

Another key factor is ecommerce, certainly at the retail level, but also for consumer goods manufacturers and even in some "B2B" sectors. In B2C, ecommerce orders almost by definition involve split case picking, as customers order a single or at most handful of items that are generally in single unit quantities.

SCDigest Says:

Each carton is automatically moved to the next zone where there are picks for it, and only those zones, significantly improving overall productivity and throughput.
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In either case, the costs of order fulfillment increases at the level of split cases picking rise. The picking cost per unit will certainly be much higher at an eaches level than they will be for full case picking, and split case picking generally tends to be more complex. A supplier that is informed by Walmart that it has been selected as a "pick and pack" supplier may hear promises of a lot more business down the road, but it will have to absorb higher logistics costs in the short term as that plays itself out.

What Can be Automated?

Given these trends pushing companies towards more split case picking, can automation provide an antidote to rising distribution costs?

Yes and no. There are some tried and true (A-frames) and newer (e.g., "spider" arm pickers, among a few others) approaches to automating split case picking, but in reality these still have a fit in relatively small segments of the markets, such as A-frames for pharmaceutical products. "Spider" technology is really just getting off the ground.

Certainly other picking related technologies, such as Voice or "wearable" wireless terminals, should be evaluated, both of which provide so-called "hands-free" capabilities that drive productivity gains versus traditional RF terminals. Voice in particular has been very popular among dedicated etailers.

But what about materials handling automation? Is there an analog to the "pick-to-belt with downstream sortation" model that has been a mainstay of case picking for some three decades?

In a sense there is. Many split case picking operations use some form of "pick and pass," where a carton for a retailer or end customer is initiated at the start of the split case picking area, and "passed" to downstream pickers in other zones where other items for the order are added, a process that repeats until the carton/order is complete.

The pick and pass process can be enhanced by using some form of "cluster picking." That means a group of cartons/totes passed to a pick zone are "batched" for picking purposes in that zone. That means that as a picker takes cartons through a zone, picks for a given SKU are sequenced so that all cartons that require that SKU are serviced by the picker before he or she moves on to another SKU/location in the zone. That in the end reduces travel time.

For large split case picking operations, the pick and pass operation can be automated in terms of carton movement, driving significant productivity gains.

In fact, SCDigest materials handling editor Cliff Holste was among the first if not the first to design this automated carton transfer approach in 1998, during an implementation at a totes Isotoner DC in the Cincinnati, OH in 1998.

Now, this approach (and supporting technology) has become much more commonplace, though still not broadly recommended by consultants and others despite its potential efficiency gains for many operations. It involves using powered conveyor to move product from zone to zone, intelligence to skip zones where no picks are required for a carton, and horizontal transfer conveyors to move cartons laterally into each pick zone.

Comparing Pick and Pass Approaches

Without going into too much system design/operational detail, let's first look at a typical non-automated pick and pass system configuration. In the typical approach, a powered takeaway conveyor line is centered between two banks of case flow racks. A dead roller conveyor is located along both sides of the powered conveyor line leaving enough aisle space for picking between the face of the flow rack and the edge of the roller conveyor.

(Distribution/Materials Handling Story Continues Below )


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All picking must begin in the first zone. A preprinted pick list is attached to an empty container (tote box or shipping carton), and the container is placed on the roller conveyor. The picker working that zone pushes the container (sometimes 2 or 3 at a time) thru the zone, picking the required product (for each container) along the way. The picker is required to check off each product picked.

At the end of the zone, the container is either complete (no more items required) or it requires items from downstream zones. If the container is complete, it is pushed onto the powered takeaway line where it is transported to order checking, packing, and shipping.

If more items are required, the container is passed onto the next downstream zone via the roller conveyor and the picking routine is repeated. The container is passed through each consecutive zone until all items on the order have been picked. All orders start in the first zone even if no picks are required in that zone. If the order requires a pick in the first and last zones, it must be pushed thru all of the in-between zones - obviously a not very efficiency process, even if over the approach is more efficiency than not using pick and pass at all.

Often, a simple paper pick list was used to drive item picking. Today, RF, pick-to-light, or Voice technologies are commonly used to drive the physical picking operation, though paper pick lists are still around. While these more advanced picking technologies have been proven to increase productivity and reduce errors, the basic flow of containers within the pick and pass system remains the same regardless of which picking technology is used - all cartons to travel through all zones until the final one.

With the above in mind, we can now look at how automated zone routing works to improve the performance of the traditional pick and pass operation.

The pictures below show a typical popup sorter embedded in the main line powered conveyor that is capable of automatically scanning and transferring containers to either the left or right side picking zones. Containers traveling on an automated conveyor system are routed only to the required pick zones, decreasing container congestion and throughput time, and drastically reducing the number of times a container is touched throughout the picking process.

Pop-Up Transfer Conveyors Used to Move Cartons into Next Required Pick Zone



This more automated approach also requires a more intelligent Warehouse Control System (WCS) integrated with a WMS.

Split case pickers would typically use RF or Voice terminals connected to the WMS and a network of printers. When the WMS downloads a wave, shipping compliant labels are printed in each carton's originating zone. The label contains a serial number bar code (often a GS1-128), and indicates what size shipping container is required (based on the total cubic volume of the required item). That label is then manually applied to the side of the appropriate shipping carton as it is constructed from supplies typically under the conveyor line.

This label is then used to drive item picking, convey and automatically sort partially picked cartons to downstream zones for additional picks, and for shipping sortation on the conveyor system.

After a carton is created the pick process in the zone proceeds, perhaps in a "train" of 3-5 cartons. Picking is against the flow of the conveyor, so that when the picks are complete the picker and conveyor are back towards the start of the zone. This is because there might be picks for any of these cartons in the zone on the other side of the current one, so the cartons need to move into or passed the transfer point again.

After all picks in the zone are performed, the WCS/WMS either tells the picker the carton is complete, or that more picks are required in a downstream zone.

If a carton is complete, the packer adds dunnage as needed, seals the carton, and places it back on the center conveyor, which sends it on to downstream sortation. (totes Isotoner has now automated the carton sealing process, which it did not do at the initial implementation). If a carton contents label is required, that is printed automatically and manually placed on the carton before it goes back on the conveyor.

If the carton still needs more picks, the carton is placed back on the conveyor, which is delivered to the next zone in which picks are required, via the transfer conveyors.

So, each carton is automatically moved to the next zone where there are picks for it, and only those zones, significantly improving overall productivity and throughput.

Hoste says that "There is no doubt about it, automated sorting when combined with zone routing and zone skipping logic, definitely increases performance and productivity of the split case pick and pass system. You have to have to right volumes and number of SKU to justify the investment, but I am confident that a lot more companies could be using this approach than are doing so today."

Have a question for Holste around the automated pick and pass system? Let us know at the Feedback button below, and he will respond.

Have any other comments about this approach? Let us know your thoughts at the Feedback button (email) or section (web form) below.

Recent Feedback

In reading this article it seems unclear whether "humans" are still involved in the picking process, with more sophisticated WMS / WCS systems the routing can certainly be made more efficient but I do not see how "eaches" can be automatically picked unless they are stored as eaches in the first place.


Feb, 14 2014