By Rob Kaszubowski, CPP
“Compression” and “stacking strength” are two terms thrown around the packaging world often as interchangeable references to the strength of a package or corrugated box. In actuality, these are two totally separate measurements of package performance and one of them has the potential to significantly impact supply chain savings.
A compression measurement describes the potential strength of a box or package. It is calculated in a laboratory environment under a dynamic, moving load (typically at a rate of ½” per minute) at standard conditions (23°C and 50% Relative Humidity). The typical testing method uses a compression table and adheres to ASTM D-642 testing protocols.
Stacking strength, on the other hand, measures the size of load a box can endure during transport, storage, and distribution. Stacking strength, or overall box performance, is tied to a number of factors a package encounters throughout its lifecycle, including pallet pattern layout, pallet quality, storage time, warehouse and transportation environmental conditions, mode of transportation, travel distance, and even the strength of the packaged product itself.
Warehouse Box Stacking
While stacking strength seems like the obvious measurement of choice, unfortunately it’s easier written about than implemented. The number of tests and length of time required to test true stacking strength is prohibitively expensive for many companies. The answer for some is to simply multiply their static load requirements by a “safety factor” to create a minimum lab compression requirement. But, considering that these factors can range from 2x up to 10x the dead load a box may see, this isn’t really the best practice.
If you truly want to design more effective packaging that strikes a balance between material and supply chain costs, then try these practical exercises to figure out what strength you really require from your packaging:
- Measure and monitor your environmental conditions during storage and transport. (Don’t forget to factor in any seasonal swings!
- Determine the amount of strength gained from product load sharing.
- Review your pallet layout patterns to see if they are optimally designed for loading, storage, and transport.
- Adjust your safety factors as you measure and monitor packaging and product damage.
- Use alternate test methods, such as dead load testing per ASTM D-4577.