In a field dominated by wood, aluminum shows promise in shipping pallet designs
November 2012 - As the most common medium between packaged goods and a warehouse floor, truck’s bed or forklift, wood pallets are a fixture of any material handling environment. Perhaps due to their ubiquity, they’re often overlooked as a point of supply chain improvement. By the same token, working to optimize them on a grand scale, as some college students did, could make material handling more sustainable.
Earlier this year, a group of Ohio State University seniors developed an aluminum pallet prototype that weighs a fraction of its wood counterparts and, presumably, lasts indefinitely. The students took on the open-ended challenge of designing a solution that reduces the material handling burden on transportation, says Dr. Glenn Daehn, materials science and engineering professor, who advised the students. The Alcoa Foundation funded the research.
“Pallets are one of those things that are all over the place, that we don’t think about very much,” Daehn says. “Their design hasn’t evolved much since the 1920s.”
Using 6061-T6 alloy, the students based the design on a 48 inch by 42 inch by 6 inch pallet, a common ISO-sanctioned size. The criteria dictated that the pallet be 100 percent recyclable, cost less than $75, have a static load capacity of 6,000 pounds and dynamic load capacity of 2,000 pounds. The students explored a variety of manufacturing methods that eventually ruled out welding. Welds done by hand, as well as automated welding, would be expensive, and applying heat to aluminum could compromise its weight-bearing strength properties. They ended up with three possible options, all weighing less than 30 pounds and costing less than $75 to make.
The lightest option, at 21.9 pounds, is a waffle-like pallet composed of four parallel U-channels connected to four 0.010-inch-thick tubes via conformal interference, a joining process using electromagnetic induction to form the aluminum.
“All the welded designs seem to be done by hand, which will never be cheap even if you make big automated fusion welds. It’s relatively slow,” Daehn says.
The other two designs—one an Industrial Origami fabrication, the other a T-beam construction—could also be manufactured with commercially viable methods (they weigh slightly more than the U-channel).
Strength in numbers
Wood pallets are cheaper than aluminum: they cost anywhere from a few bucks up to $20. And 90 to 95 percent of all pallets are wood, so they’re not going away soon. Plastics and composites make up about 2 to 4 percent, with metal pallets making up the rest of the share, according to the Material Handling Industry of America, a Charlotte, N.C.-based trade group. Existing aluminum pallets can cost $200, but the payoff lies in the long-term usability.
One Phoenix-based company, Eco Aluminum Pallets, has been producing aluminum pallets for about two years and is one of the few U.S. companies to do so successfully. Eco’s design is similar to the prototype at Ohio State: the pallets are modular, customizable, extruded panels that are interlocked, rather than welded or bonded, which keeps the prices closer to the $100 mark.
Steel pallets have been around longer, but they’re heavy and can rust, says Peter Johnson, Eco’s president. Aluminum, along with its lightweight and recyclability, doesn’t rust, making it ideal for overseas travel. It’s also conducive to shipping medical, food and pharmaceutical goods, as aluminum naturally is toxic to bacteria.
“When we were coming up with our concept and researching the market, we found aluminum to be the best product out there,” says Johnson.
Eco’s pallets mainly are viable in closed-loop environments where companies maintain pallet possession, as opposed to wood ones that are shipped one way and used for two or three trips. Many of Eco’s clients are manufacturers of high-dollar medical or aerospace heavy equipment and can’t afford to worry about a wood pallet breaking.
“If you’re buying those wooden pallets every month, that five dollars adds up,” he says.
The environmental benefits are myriad with aluminum as well, Johnson says. It keeps wood pallets out of landfills and reduces the reliance on lumber. The company estimates 1 million acres of trees in the U.S. alone are cut to manufacture pallets. Aluminum doesn’t burn either, limiting the risk of fire damaging both the pallet and product.
As lightweighting efforts are driven by automotive and aerospace industries in particular, cutting the loads those cars and planes carry bolsters fuel efficiency, ultimately cutting costs at each step of a supply chain. At Ohio State, the pallet project isn’t headed for production, but Daehn says he’s had plenty of phone calls from interested people in the shipping and transportation industries.
“We felt generally more committed that this was a good idea as we went down the pipeline,” he says. MM