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How We Spec Cushioning for Drop Tests
A drop test is not a formality. When a parcel leaves your dock it will be dropped, tossed onto a belt, and stacked in a truck, and the insert is the only thing standing between that abuse and your product. Spec’ing cushioning well means the product arrives intact; spec’ing it by feel means you learn the hard way, one damaged return at a time.
Here is how we translate three inputs — fragility, weight, and drop height — into a concrete spec: a foam type, a thickness, and a bearing area. The goal is simple to state and precise to execute: keep the peak deceleration the product feels below the point where it breaks.
Start with fragility: the G-factor
Every product has a fragility rating expressed as a G-factor — the number of g’s of deceleration it can survive before something fails. A rugged hand tool might tolerate 100 g or more. A hard drive or a bare sensor assembly might fail below 40 g. The lower the G-factor, the more cushioning the product needs. If you do not have a measured fragility value, we estimate from the product class and design with margin, then confirm on a physical sample.
Add weight and drop height
Weight sets how much energy the cushion has to absorb, and drop height sets how fast the product is moving at impact. A heavier product at a taller drop delivers more energy, which pushes you toward firmer, thicker foam. Drop height is not a guess: it is defined by the shipping standard for your parcel’s weight class, which is why we design against a target rather than a hunch.
Turn inputs into a spec
The three inputs map onto three outputs. Foam type and density set the cushion curve. Thickness sets how much distance the product has to decelerate over — more thickness lowers peak g’s, up to a point. Bearing area, the footprint of foam under the product, sets the static loading; too little area and the foam bottoms out, too much and it is too stiff to cushion. We tune all three together so the product lands in the sweet spot of the foam’s performance curve.
| Input | Drives which output |
|---|---|
| Fragility (G-factor) | Foam type and target peak deceleration |
| Product weight | Foam density and bearing area |
| Drop height | Foam thickness |
| Number of impacts | Closed-cell choice for repeat recovery |
Cushioning is an engineering problem, not a guess. Fragility sets the foam type, weight sets density and bearing area, and drop height sets thickness. Get those three right and the product stays under its failure threshold on every drop of the test.
Design against ISTA
ISTA test procedures — such as the widely used ISTA 3A for parcel shipments — define the drop heights, drop sequences, and impact orientations a package must survive. We design cushioning against the relevant ISTA target for your weight class so the insert is built to pass a recognized standard, not just to look protective. That gives you a defensible spec to show retailers, carriers, and quality teams.
Prove it on a real sample
Calculations set the starting point; a physical prototype confirms it. Because we hold a ±0.5 mm tolerance, the sample you approve matches production, so a drop result on the prototype carries through to the run. We cut a proof in 24–48 hours, you test the fit and protection, and we adjust density or thickness before committing to production in 7–10 business days.
Have a drop-test target to hit?
Send your product weight, fragility, and the standard you need to pass. We will engineer the cushioning and cut a proof to test.
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To pick the foam family behind the spec, read PE, PU, EVA & ESD Foam Explained. Still deciding between materials? See Foam vs. Cardboard Inserts: How to Choose. When you are ready to gather everything we need, use our spec checklist, or browse the products page.