Why do cartons arrive crushed even when the master carton passed its drop test?

Main answer · Wecent Editorial Team

Short answer: A drop test checks impact, but crushed cartons usually come from stacking load, humidity and pallet handling over days or weeks, which a drop does not measure. A carton that survives a one-metre fall can still collapse under a tall stack in a humid container. Test compression and the whole shipping chain, not only drops.

What each test shows

A drop test checks that the carton and contents survive an impact. It says little about what happens to the bottom cartons of a pallet that sits under weight for weeks, in changing temperature and humidity.

Common causes of crushing

• Stacking height. The load on bottom cartons grows with every layer above. A tall pallet needs stronger cartons than a short one.
• Board strength. The grade, flute type and number of walls of the corrugated board set its compression strength.
• Humidity. Corrugated board loses a significant part of its strength when damp, and sea freight exposes cartons to moisture.
• Pallet pattern. Cartons overhanging the pallet edge or stacked in an unaligned pattern lose strength at the corners.
• Void fill. Gaps inside the carton let contents shift, and the carton walls take the load instead of the product.
• Handling. Forklift clamps, rough loading and slings add crushing force.

What to test and specify

1. Compression strength of the carton, measured and compared with the load it carries at the bottom of a stack.
2. Humidity conditioning before testing, since dry results overstate real strength.
3. Vibration and stacking on a pallet for a period similar to the journey.
4. Pallet drawing showing layers, orientation and maximum stack height.

What to ask the packaging supplier

Ask for the board specification, the tested strength, the maximum recommended stack and whether the figures are for dry or humid conditions. Request a test report from an independent lab for a new carton design.

Practical fixes

• Reduce stack height or add layer pads.
• Upgrade the board grade for the bottom layers.
• Use corner protectors and stretch wrap in the right pattern.
• Fill gaps inside the carton so the load goes through the product, not around it.
• Add a moisture barrier or desiccant for sea freight.

Document the problem

Photograph crushed cartons at arrival and record their pallet position. The pattern tells you whether the problem is board strength, stack height or handling.

Where this answer says to confirm with Wecent, the detail is not published on the product page and has to come from the datasheet or the factory. General facts come from the regulators, standards bodies or device makers named in the text.