What is a Cushioning Curve?


Most people in the packaging industry know about cushioning curves, but that’s where their knowledge ends.

We know they are important and it helps to design packaging, but how does it work?

When working with cushioning curves, it requires several pieces of data that are often unknown: so how do we use it?

What is a Cushioning Curve?

A cushioning curve describes how a specific packaging material at a specific thickness will behave at various impact conditions.

a generic cushioning curve

The graphic above is a generic cushioning curve

In layman’s terms, we’re trying to figure out: how high and fast can I drop or throw this package before the product inside is damaged?

If we know that, then we know what conditions we need to ship these products and what specific combination of packaging material + thickness we need to choose to offer the best protection to the product.

How to Calculate a Cushioning Curve

To get started, here is a list of the data we need:

  • Weight of the part
  • The number of G’s the part can withstand before getting damaged
  • The shipping environment

The vertical axis on the graph is the amount of G force, which is calculated by dividing average acceleration by the acceleration due to gravity. More reading can be found here, but for the sake of this blog we will refer to it as the amount of force.

The horizontal axis is the PSI (Pounds per Square Inch) of the foam supporting the part. PSI is calculated by taking the weight (in pounds) of the part and dividing the surface area of foam supporting the part (in square inches).

For example, a 10-pound part supported by 10 square inches of foam will have a PSI of 1. A 10-pound part supported by 5 square inches of foam will have a PSI of 2.

Now that we have the axis defined, what does the plotted line mean? The plotted line is the amount of G force applied to the part at various PSI’s. In order for this to make sense, we need to add values to the axis.

a graph showing a cushioning curve with two dots on points in the line - one blue and one red

In the example above, the 10-pound part would sustain 40G’s of force if 10 square inches of foam is used (Blue). Alternatively, the 10-pound part would sustain 60 G’s of force if 5 square inches of foam is used (Red).

As long as the point on the cushioning curve is lower than the amount of G’s required to damage the part, the packaging is sufficient.

How to Use a Cushioning Curve to Choose Foam Packaging

Different shipping environments will subject the packaging to various forces. A refrigerator is going to be handled differently than a laptop computer. A laptop will be handled by a delivery person who may drop it from a height of at least 48”, where the refrigerator is unlikely to be lifted higher than 12”. Each foam material has a different curve for the various drop heights.

The thickness of the foam is another consideration that will drastically affect the packaging performance. There is a different cushioning curve for 1”,2”,and 3” thicknesses. Some foams have cushioning curves up to 5” thick. The calculations are all the same for each curve, but using all of the data above will help determine how to use the least amount of foam possible, which will help cut packaging costs.

Most companies do not know how many G’s of force their part can sustain before failure but the experienced designers at Foam Industries can help determine how much protection is needed.

Contact a Packaging Expert

Foam Industries is a custom protective packaging company specializing in foam – with additional wood and plastic fabrication services. Our custom foam fabrication services are ideal for any type of packaging, display, or support service needed – from design to finished product.

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