Unit load handling redux

Are unit loads still relevant in a world of eaches?

Youbetchya!

In fact, unit load handling might be even more important now. “It’s all about minimizing the number of touches and integrating reserve storage with order selection processes,” explains Dan Labell, president of Westfalia.

And that’s not easy to do inside the four walls of most distribution centers or manufacturing sites. The many order complexities in warehouses and production requirements in manufacturing facilities are anything but a single SKU pallet load. You know, rainbow pallets, layered pallets and more. Touches are inevitable but minimizing them is possible.

To manage it, system suppliers are coming up with creative system configurations and equipment to put away, pick and transport unit loads both within the storage system and out on the floor.

Some options include shuttles, automatic guided vehicles (AGVs) and autonomous mobile robots (AMRs). All three make new unit load flow possible and practical. And flow both within and outside the unit load storage system are equally critical.

As Dematic’s senior solutions consultant Cris Stevens points out, all of that is about the four concerns he finds top of mind. “Users are clearly focused on system uptime, flexibility, redundancy and cost,” he says. Better yet, he adds, all of that can be accomplished.

And your peers are responding to their options here, says Ben Lee, vice president of sales for integrated solutions at Swisslog.

Lee expects strong demand for unit load systems for at least the next three years. He says demand is actually in a catch-up phase after project delays in 2022 and 2023. However, that is pretty much behind us, Lee says. And he is not alone in that assessment.

All of which brings up the question: What exactly do you get for your money?

New unit load profiles

“Unit load solutions and the handling techniques are getting better and more advanced in their design,” says Jake Heldenberg, Vanderlande’s head of solutions, warehousing. “Unit load handling is not going away. But it is changing,” he adds.

Westfalia’s Labell says picking the right system is all about focusing on the value streams in the operations performed in the facility.

Is it only handling full pallet loads? What about layer picking for rainbow pallets? Or even case picking? Quite simply, your operations directly impact what a unit load system looks like today.

That said, let’s focus on equipment to start.

All rack is just rack. Right? Yes but no by the time you get to double-deep or deep lane storage. Here’s that story.

The vast majority of the installed base of unit load automated storage and retrieval system (AS/RS) solutions puts rack one pallet load deep on each side of an aisle serviced by a single storage retrieval machine (SRM). That’s a simple and proven solution. But it’s not always the full answer.

There can be, of course, pallets stored two deep on each side of the aisle. And if you’re going for even higher storage density, some or all of those two pallet deep positions could actually be several pallets deep on each side of the aisle.

Typically, a low-profile bot, also known as a shuttle, is carried on the SRM to the lane housing the needed pallet. The bot is dispatched by the SRM into the lane to run down to the pallet, lift it slightly and carry the load out to the SRM that travels the aisle to a drop off station.

You can already see the limitations to all of these systems. While storage density options are available, there is still typically a single SRM or even a second in an aisle to transport pallets one or two at a time. And while redundancy here does add flexibility, many operations will have throughput limitations.

Picking up the pace

That’s where pallet shuttles come in, going far beyond deep lane storage. Shuttles are typically independent, low-profile bots that travel in a rack configuration, bringing a unit load to a designated drop off location. Often, you have multiple shuttles to get as many pickup and delivery streams possible going at once without running into each other.

“Pallet shuttle systems,” says Dematic’s Stevens, “store, buffer and sequence products between bulk stock and other functions such as production, order fulfillment and shipping. They can dramatically increase speed, storage density, accuracy and throughput.”

While many pallet shuttles are dedicated to a single level in the AS/RS, Movu is one company with pallet shuttles that can be moved between levels. The shuttles carry loads through specially configured rack, working one level at a time, explains Thomas Meyer-Jander, Movu’s chief marketing officer. An elevator located strategically in the storage system moves shuttles to a designated drop off point for a level change.

He explains that shuttles, which can be used in both ambient and cold storage facilities for loads up to 1,500 pounds, can easily be added or removed as demand ebbs and flows. Shuttles can also be redirected to different levels as needed.

Movu also offers an AMR for load transport on the floor of a facility. This is much the same as Dematic, which uses one form of AGV design to move loads within rack and different design to move loads on the facility floor to other designated destinations.

In all designs, software is critical, explains Swisslog’s Lee. It directs pallet movement in line with orders and ensures multiple shuttles, AMRs and AGVs don’t run into each other. A direct link to a warehouse management system (WMS) or manufacturing management system is common.

Another core software functionality, says Lee, is system condition monitoring. And, of course, issue resolution needs to be as quickly as possible. This plays directly to the uptime mentioned earlier.

Lee expects that going forward artificial intelligence will play a role in condition monitoring and resolution. This is sure to improve uptime. By the way, Lee is fond of saying: “the only thing that matters is uptime.” He does make a point.

This is also where redundancy and flexibility mentioned earlier occur and are so important operational efficiencies.

But the battle for both redundancy and flexibility does not stop at shuttles. AMRs and AGVs can both take the place of bots and shuttles to provide additional speed and flexibility without pushing cost out of sight.

Still more options

Needless to say, equipment and software don’t do it all. Unit load system configuration is critical.

We’ve already covered multiple shuttles/AMRs on multiple levels. Dematic’s Stevens goes on to name six more:

1. Storage lanes used for transport of loads to other areas of the building;
2. Multiple drop-off points based on proximity to the load’s destination;
3. Storage lanes used for inter-aisle transfer;
4. Integrated sub-aisles for slow movers;
5. Integrated shipping buffer/sequencing to shipping; and
6. Dynamic lane depth and virtual configuration.

And if you gave Stevens five more minutes to think about it, he’d probably come up with several other valuable options for unit load system configuration.

Both sides of the coin

One thing is clear about the future of unit loads—established technology has its place just as much as the latest development does.

To make that point, here are two condensed case histories. One with Anheuser-Busch using a more conventional SRM and the other of a European third-party logistics provider (3PL) using AMRs.

Anheuser-Busch wanted to improve its customer response time and reduce warehouse operating costs at its brewery in Columbus, Ohio. The list of required improvements included improved product damage and aging control as well as reduced load time for wholesaler trucks. Clearly, their unit load storage systems are not islands.

The outcome is a system that holds nearly 13,000 pallet loads and has a throughput rate of 680 pallets an hour with seven, dual-load SRMs in seven aisles. Forty AGVs move loads at a time to shipping docks. Those dual-load capabilities allow the brewer to turn over the warehouse’s entire inventory in two days.

Controls manage AGV scheduling while customized inventory control software manages inventory flow. A real-time interface connects with Anheuser-Busch factory control software.

When a wholesaler truck arrives at a check-in station, an order is released to the SRMs and AGVs. By the time the truck arrives at the dock, unit loads are staged and ready for loading.

Meanwhile, over at logistics service provider Kris De Leeneer, shuttles are used to maximize flexibility and pallet throughput. The system has 45,000 storage locations and can make 11,000 pallet movements a week.

The 3PL does that with 20 shuttles from Movu. Meyer-Jander says “these self-powered robotic carriers transport pallets on the rails of the rack’s storage lanes. A WMS manages shuttle movements. By the way, authorized operators can control the system with an app on their phone.”

He continues to say that in a typical hour, 150 pallets are inducted to the system and 150 are picked and removed. Meyer-Jander adds that each shuttle can be reassigned to different levels based on volume requirements at any given time.

Also, the AS/RS delivers loads to a mezzanine for value-added services as well as to designated piece picking areas.

So, just when you feared unit load handling was at the end of its run, it clearly isn’t. In fact, you now have more options than ever.