Typically, the compression strength of boxes is increased by adjusting board grade and flute type. Pallet stiffness, however, also plays a role.
One version of the pallet stiffness story goes as follows. An FMCG (fast-moving consumer good) manufacturer is surprised to receive reports of their boxes bulging at the sides, resulting in unit load instability and crush damage to products. Multiple claims are being forwarded by customer service. The packaging buyer is perplexed. Nothing is seemingly different in packaging and logistics than how things have been for the last few years, and yet now there are problems with corrugated packaging not performing the way it has until this point in time.
The packaging buyer wonders if the supplier has tried to slip them inferior packaging. The packaging supplier strenuously protests that nothing has changed regarding the boxes supplied. A relationship of trust built over time seems to be unraveling.
But one change may have been overlooked – pallet stiffness. One way that pallet buyers can save money on pallets is by accepting thinner deck boards. A ⅜” deck board, however, does not provide the same level of stiffness as a ⅝ deck board. Could the procurement department have inadvertently caused their own problem by going to a thinner deck board to reduce pallet cost?
I recently reached out to Page Clayton, packaging sales engineer with Litco International, to discuss the issue of pallet stiffness. He explains that stiffness relates to the pallet’s resistance to deformation when under load.
The root problem, he notes in the Litco white paper, A Comparison of Pallet Strength and Functionality, is that a pallet is not considered a value-added component but a commodity to be purchased for the lowest price. This misconception leads to improperly matched packaging and pallet designs, resulting in excessive damage due to unintended unit load interactions and warehouse damage. The assumed cost savings when using pallet price as a decision driver, he concludes, turns ultimately into a financial liability with damaged product returns and unhappy customers.
Why is pallet stiffness significant?
So why does stiffness matter? “If the pallet is not stiff enough,” Clayton explains, “the boxes will deform with the pallet. If the pallet bends, then there is no longer symmetrical contact between the box and the pallet deck. Because of the pallet bending, there’s less contact with the product on the top pallet surface and that increases the concentrated pressure points per box.” If bottom boxes experience too much pressure, he adds, then it may cause damage to the product within them.
Stiff pallets also help reduce vibration, which is critical for sensitive products such as electronic equipment. A server rack, for example, can have a computer chip on a motherboard that may be sensitive to a particular vibration range. “As a packaging engineer,” Clayton states, “you can decide, whether to add additional packaging to 100 graphics cards to change the frequency, or you change the pallet stiffness. With a stiffer pallet, perhaps you don’t have to buy 100 foam elements for that whole shipment of graphics cards.”
The importance of pallet stiffness is underscored in a research paper by Virginia Tech, The effect of pallet top deck stiffness on the compression strength of asymmetrically supported corrugated boxes. Researchers noted that the necessary compression strength of a palletized box could be attained by designing the unit load in multiple ways. Typically, the compression strength of boxes is increased by adjusting board grade and flute type. Pallet stiffness, however, also plays a role.
Stiff pallets can increase box compression strength by 27-37%
Researchers found a 27-37% increase in box compression strength for boxes supported by high stiffness pallets compared to low stiffness pallets. The fact that boxes were weaker on low stiffness pallets, the paper notes, could be explained by the uneven pressure distribution between the pallet deck and the bottom layer of boxes.
A company migrating from a 9.5 mm deck board (low stiffness) to 15. 9 mm (medium-high stiffness) could achieve packaging reduction savings of $1.84 per unit load or up to $1,840,000 for a company shipping one million pallets annually.
When it comes to wood pallets and stiffness, thicker deck boards are better. Stiffness is also an essential consideration for alternative material pallets, such as plastic. Plastic pallet stiffness is improved by the use of steel or fiberglass inserts.
One high stiffness alternative material pallet is the Litco Engineered Molded Wood™ Pallet. “The deck of the Inca (Litco) pallet is at least six times as stiff as the deck of the GMA pallet,” wrote Dr. Marshall White in the Litco white paper. “This will result in more stable unit loads during shipping and handling and less product damage resulting from load slip on the pallet.”
While stiffer pallets can provide an opportunity to save on packaging due to uneven box compression and reduced vibration, they also have other benefits. Material handling equipment operators more readily handle stable unit loads. They may require less wrap to stabilize and are less prone to load shifting, an issue that can require forklift operators to work more slowly. Deformed deck boards sagging under load can also interfere with entry by pallet jacks into the pallet, wasting time and potentially destabilizing the unit load.
The cheapest pallet often does not provide the best overall value for your supply chain. Pallet stiffness is important and should be evaluated in harmony with box design.