December 1, 2008
equipment & applications | Cubing & Weighing

Cube route to better slotting

cube route to better slotting

Capturing precise dimensions of the SKUs in your DC can help make more of your storage space. And tape measures may not be up to the task.

By Peter Bradley

In DC operations across America, "guesstimates" may be going the way of the dodo. Over the last couple of years, operations managers have had to pay much closer attention to the size of their outgoing shipments.

The new emphasis on precision is a response to parcel carriers imposing and enforcing so-called "dimensional weight" rules. Under those rules, shipping charges, particularly for large, lowdensity packages, are more likely to be based on a parcel's "dimensional" weight—a computation that includes its length, width, and height—than on its actual weight. Rate a package incorrectly, and you're likely to be hit with charge-backs and penalties.

To avoid those fines, many shippers have turned to dimensioning, or "cubing," systems. As a result, these devices, which use sensors or lasers to automatically gather dimensional and weight data, are fast becoming fixtures on shipping docks nationwide.

That same equipment, it turns out, can contribute to efficiency on the receiving dock as well. In fact, dimensioning systems were initially developed for the back end of the warehouse. Here, the systems are used to record the dimensions of individual products or cartons, as opposed to entire shipments, for use in storage, or "slotting," assignments. Capturing accurate dimensions of all incoming products can help users make slotting decisions that lead to more efficient use of DC storage capacity, says Steve W. Trommer, vice president of Trommer & Associates, a consulting firm that specializes in facility design and material handling.

Of course, slotting decisions involve a lot more than determining the most efficient use of storage space. Factors such as how quickly SKUs turn and what products tend to ship together are all essential to good slotting decisions.

But accurate physical measures are nonetheless an important part of those decisions. And it's not a static issue. Products change, and so, too, does product packaging. If the facility fails to capture those changes, DC slotting efficiency will diminish over time. Trommer says that's something DC managers often overlook when considering possible causes for declining productivity. "When operations managers come to us, they may be looking at inventory quality, but they have never re-profiled their material handling system," he says. "They may be using a six-foot space for a product that now comes in a smaller volume or in less than pallet loads."

Quick returns
Trommer advocates that companies invest in dimensioning systems like the Cubiscan line of dimensioning systems from Quantronix or similar tools sold by Mettler Toledo, arguing that buyers can expect a quick return on their investment. That's largely a result of labor savings, he says. To illustrate his point, Trommer cites slotting projects his company completed for two customers with similar SKU profiles. One, using a cubing tool, captured the cube and weight of 721 SKUs in three days. The other, with employees using tape measures, needed three weeks to capture the dimensions of 750 SKUs.

"A cubing device can save an enormous amount of time measuring a large number of items," says Randy Nielsen, vice president of Quantronix. He says the company's Cubiscan 100 model, for example, can capture the dimensions of more than 100 items an hour.

Trommer further argues that dimensioning systems are much more accurate than workers measuring by hand. Tape measure readings are subject to interpretation, he explains, and even slight variations in readings can have a big effect on productive slotting. "If you are off by a half inch," he says, "that can have a large impact on the days of inventory in a flow module."

Current cubing systems offer accuracy of two-tenths of an inch or better, manufacturers say. Some of the systems aimed at the distribution and warehousing markets have even closer tolerances, with some small devices offering accuracy down to one one-hundredth of an inch for products like books and CDs. Nielsen says that for warehousing and distribution applications, accuracy to one-tenth of an inch or better is essential.

The best systems for slotting
For applications like capturing data for slotting, static systems, as opposed to inmotion systems mounted over conveyors, appear to be the tool of choice. Manufacturers offer a range of those products, from devices aimed at capturing data from items as small as CDs up to pallet dimensioners.

The systems also have the advantage of being user friendly, Nielsen says. "Our static systems are user installable and user maintainable," he says. "The customer can open the shipment, unpack the device, load software to its PC, plug it in, and away they go. You can be up and running within an hour."

As for the procedural side of the dimensioning process, Trommer says the easiest way to capture dimensional data is to measure carton sizes as they arrive. But that leaves the question of what to do about slower movers that may not arrive during the time period set for a re-slotting project— say, a month or so.

Trommer says in those cases, the easiest thing to do is go out and capture data at the items' current locations. Many of the cubing devices on the market today are designed to mount on portable carts for that reason. The mobile cubing systems run on battery power and can feed information as it is captured into a PC on the cart or, through a wireless connection, directly upload it to a warehouse management system or an enterprise resource planning system, he says.

Most modern WMS and ERP programs have built-in fields for capturing weight and dimensional data, he adds. "If you have a legacy system, you have more of an issue. You may have to go back to the programmers."

Nielsen expands on that point: "The whole goal is to eliminate or, in some cases, minimize the work the IT department has to do to adjust or tweak the WMS. We've taken a look at a lot of WMS, TMS, slotting, and manifesting software and come up with software systems that are virtually plug and play. There will always be some exceptions, but very few."

Standard equipment?
Right now, cubing systems are generally considered optional equipment for warehouses, but that might be about to change. The ability to capture and upload dimensional and weight data quickly may become an imperative for DC operations. "Industrial engineers are making it mandatory," says Jerry Stoll, marketing manager for Mettler Toledo, a Switzerland-based manufacturer of scales and cubing equipment. "Companies are more stressed to save pennies."

Stoll adds that precise dimensional information can prove useful for purposes other than slotting. For instance, accurate size and volume information also helps managers allocate operational costs to products based on the space they occupy in the DC.

But whatever the end use, one thing remains the same: The first step is taking the measure of the goods.

About the Author

Peter Bradley
Editor Emeritus
Peter Bradley is an award-winning career journalist with more than three decades of experience in both newspapers and national business magazines. His credentials include seven years as the transportation and supply chain editor at Purchasing Magazine and six years as the chief editor of Logistics Management.

More articles by Peter Bradley

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