Shipping Pallets: The science behind unit load design
August 07, 2012 - MMH Editorial
For the past five or six years, Mark White, president of White and Company and a professor emeritus at Virginia Tech, has been preaching the benefits of a systems-based approach to unit load design.
White’s idea, as I’ve written in the past, is that pallets, industrial packaging and materials handling systems are too often designed in a vacuum. The folks designing pallets never talk to the packaging engineers, the systems engineers or transportation people who are shipping a product. The result: the money saved by designing the conveyor system a certain way may be lost many times over in extra pallet and packaging expenditures.
The latest research coming out of Virginia Tech on pallet design puts new science behind that concept. White presented his findings at the ISTA Annual Conference in April. You can view the presentation here.
The bottom line on the research is that it demonstrates how a pallet designed for stiffness instead of just strength can result in a significant reduction in the overall cost of a unit load. “I have worked with several companies that have spent an additional $1.50 on their pallet but reduced the overall cost of shipping a unit load by $6 to $7 per load because they can reduce the mil thickness on the pails they ship their product in,” says White.
Here’s what the research shows and how he gets to those savings. Pallets are typically designed with strength in mind – that is getting the right thickness so that the deckboards don’t break or the stringers collapse during handling. Without question, strength is important. But the new research conducted by one of White’s research students demonstrates that a stiffer pallet can resist stress as it moves through the supply chain. That can lead to lower overall packaging costs.
“If you think about how product moves, the majority of the mechanical stress to which packaged product is exposed in the unit load has to work with a pallet,” White says. “We’re talking about pallets in racks, double and triple stacked on the floor, picked up and moved with a lift truck or the vibration experienced as a truck moves down the road. All those stresses go through the pallet first.”
White and his students have been looking at how the pallet reacts to those stresses for years. More recently, his team looked at whether they can predict how much compression stress a packaged product will be exposed to as a function of the pallet design and whether that compression can be mitigated by altering the pallet design. Voila, White says: “It worked.”
Why compression strength? “That’s how much force there is on that packaged product sitting on a pallet when you stack two or three unit loads high in the warehouse,” White says. “Compression strength is what manufacturers of corrugated cartons and plastic pails and bottles design to. If we can reduce compression stress through the pallet design, they can reduce the amount of rigid packaging in the unit load.”
That’s important because the cost of rigid packaging – the cost of all those containers, pails and bottles that sit on top of a pallet – is a lot more than the cost of the pallet itself.
The research demonstrates that the pallet amplifies the compression stress to the product in storage by a factor of 5 to 10. The flip side is that a stiffer pallet – one redesigned with thicker deck boards – can cut the compression stresses in half.
That’s why a $1.50 investment in thicker deck boards than are required from the perspective of strength alone can deliver an overall savings of $6 to $7 because of thinner pails and still transport a load through the supply chain without damage.
“Pallet strength is still important,” White says. “You don’t want a pallet to collapse. What I’m proposing is that packaging engineers and pallet designers understand that pallet stiffness is a close second.”
The new research will be incorporated into the unit load and pallet design short courses offered at Virginia Tech this fall.