Calculating Corrugated Box Compression Strength Requirements for Transit:
During Storage & Transit of the goods, which are packed in Corrugated Fibre board (CFC's) Boxes, the strength of the CFC's goes on decreasing over time, owing to the external environmental conditions and inherent property of the material , from which the box is manufactured.
External Factors: Such as vibration, shocks, Jerks, load on CFC Etc. causes reduction in the Compression strength of the Box.
Internal Factors: BOX is made out of Paper, which in turn is made out of pulp (Fibre's) of wood.
The fibre's are hygroscopic in nature and when there is excess humidity in the atmosphere, it tend to absorb the excess moisture present in atmosphere to attain equilibrium. The paper board becomes soggy and hence the Box strength goes on decreasing.
To arrest this lowering in the strength of CFC, we usually keep the factor of Safety while designing of CFC's.
Factor of Safety: this term is used to take care of external factors such as Humidity, Temperature, excessive handling, Prolonged storage etc.
In general it is safe to keep the safety factor of CFC as 2.5 to 3 , if the CFC's goods storage & transit period is about 6 Months.
How to design CFC for optimum Compression Strength
1. While designing CFC's for transport through standard containers (20 Feet, 40 Feet), please ensure that the maximum height of the container will be utilized.
2. Based on container height and products height, Design a CFC which will have optimum specification and which will properly occupy the container Height.
3. Divide Container Height/CFC height. you will get the total Stack height of the Boxes.
For Eg., if the stack height of Boxes is 8 then it means, on Bottom Box, 7 Boxes will be staked.
4. Check the gross weight of one Box.
5. multiply Gross weight of box x (Stack height -1), this will give you the total weight which is being applied on the bottom box.
6. For E.g. in this case Total Stack Load= 8
Gross Wt. of the Box= 12 Kg
therefore, Total weight on Bottom Box= 12 x 7= 87 kg
Hence keeping the safety factor = 3
The compression strength of the box should be = Minimum 261 Kg.
A standard CFC of 5 plies with Ply structure of 150/120/150/120/150 & a Burst Factor of 20/18/20/18/20 gives minimum compression strength of 280 Kg.
