- WHAT: Test compressive strength of a corrugated box
- WHY: To measure the stacking strength of a pallet load
Box compression test, also known as container compression test, is a way to test how much load the box can take on top of it before it gets deformed and the extent to which it gets deformed. It gives us a good idea of how many boxes can be stacked together without damaging the contents of the lowermost box. This test is crucial to check the strength of boxes and is required by most industries transporting boxes in bulk.
The boxes are tested in different orientations. If the box design makes use of inner supports, such as wood support or corrugated board cushioning, then such factors are also taken into account.
The compressive strength of a corrugated box can also be calculated using the McKee formula where the Edge Crush Test (ECT), Caliper or corrugated board thickness (CBT) and box perimeter (P) values are taken into account.
As per the McKee formula: Compression Strength = 5.874 * ECT * CBT0.508 * P0.492
There is also compression strength tester through which this test can be conducted.
Client will mention the CS value to the box manufacturer. This depends upon the stacking , transportation type , period of stacking during transportation or storage , type of travel route ( bad roads, water or shaky transport, hill travel) etc.,
For example: the box may be for a banana which will be stacked around 5 boxes above each other. Each box May weigh around 12kgs. So the total weight is 60kgs. Considering the palleting and transportation the client may ask 300KGS CS VALUE. So the material quality and ply type are selected based on that during product development.
The box will be placed in the compression strength tester between two plates.
The machine platens will start coming closer to each other . This will put set weight load on the box. The box will crush at a specific load weight. This value is checked on the display.
Since the client asked for the specific load value as 300 kgs , the box should not fail less than 300. For safer side manufacturers keep little extra value than client specified value.
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