If you’re involved with designing or procuring packaging, you probably know about cushioning curves - but if you’re like most people in this industry, that’s where your knowledge ends. Many people know that they are important and you have to keep it in mind when designing packaging, but what are they and why do they matter?
Additionally, when working with cushioning curves, it requires several pieces of data that are often unknown: so how do we create something concrete from so many what-ifs?
Let’s explore what you need to know and why understanding cushioning curves unlock the secret to optimizing packaging costs.
What is a Cushioning Curve?
At a basic level, the cushioning curve measures the thickness of packaging material and how it behaves under force. At a more detailed level, a cushioning curve describes how a specific packaging material at a specific thickness will behave at various impact conditions.
In the packaging industry, this term is important because it helps determine the least amount of foam a product needs during shipping to reduce costs while also keeping the shipment safe. With greater force and a larger PSI, the amount of foam needed increases.
The graphic above is a generic cushioning curve - specific types of foam have different cushioning curves, explored later in this article.
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 calculate a cushioning curve, you need a few pieces of information, including:
- Weight of the product/part/object to be shipped
- The number of G’s the part can withstand before getting damaged
- The shipping environment
This will be inputted into a graph that you can use to pinpoint the cushioning curve. Let’s revisit our earlier example of a typical cushioning curve:
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. For this blog, we won’t go too far in-depth on what G force is and how to calculate it - for that education, check out this article from Sciencing: How to Find Acceleration in G's.
The PSI (pounds per square inch) on the horizontal axis of the graph is determined by dividing the product weight (in pounds) by the foam’s surface area (in square inches). For example, a 10-pound object with 5 square inches of foam will be 2 PSI.
Now that we have the axis defined, we can add a plotted line to our graph. This line is the amount of G force applied to the part at various PSIs.
Let’s walk through a real example to help put this into practice and make the terms above clear.
Example Cushioning Curve Calculation
Let’s take an example by plotting the G force and PSI for a part at different weights.
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.
What’s the Difference Between Cushioning Curve, Tensile Strength and Tear Strength?
Damage by direct force (aka dropping or throwing) isn’t the only pressure a piece of foam may be subject to: foam can also tear and rip apart completely. Obviously, you want to avoid all three types of damage when selecting your foam.
For that reason, foam spec sheets also include information about tensile and tear strength. Tensile strength measures how much force a material can withstand before it breaks, while tear strength measures how much force it takes to break a material with an existing tear. You can explore more about these two vital measurements on our blog: Tensile Strength vs Tear Strength for Foam Packaging.
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 cushioning curve is a huge part of selecting the proper packaging for products. Keeping in mind how large a product is or how high it will be lifted helps determine just how much packaging is needed. While some items are huge, they often aren’t lifted as high as smaller products. But every product is different and needs to be measured accordingly. While the cushioning curve calculations are a similar shape between products, the amount of packaging, type, and thickness changes the values – especially when trying to reduce packaging costs.
The thickness of the foam is another consideration that will drastically affect the packaging performance. There are different cushioning curves 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.
Get It Right - Work with a Foam Packaging Expert
Fortunately, you don’t have to worry about the physics and hefty calculations we’ve outlined above with the help of Foam Industries. As a leader in the packaging industry, Foam Industries has set the bar with an unwavering commitment to quality, exceptional client service, and constant innovation. Through our extensive inventory of endlessly customizable products, we ensure you find exactly what you’re looking for.
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.
