What drop height can a shockproof case take?

A: It depends. 25 mm of foam with a 1.2 m drop peaks near 48 g; for 1.8 m the stroke rises to 40–50 mm.

Is thicker foam always better?

A: No. Thickness must match the drop, or the load shifts and strikes harder.

Can one case serve shock and dust duty?

A: The shell can, though seal and foam are verified separately and cannot simply be copied.

Does an empty case survive a drop?

A: Poorly. With no mass on the foam, the shell takes the whole impact and corners crack first.

When should the foam be replaced?

A: When compression set exceeds 10% of thickness, typically after two to three years. ---

Shockproof Case Explained: Cushioning, Restraint, Load Path

Quick answer: A shockproof case is not a thicker box. It splits one impact into three stages: the shell spreads a point load into an area, the foam flattens the peak, the lining holds the load still so it cannot strike twice. Break one stage and the other two lose their effect.

What a shockproof case is: one load path
Impact: g values and drop height
Cushioning: foam thickness and density
Restraint: constraint is cheaper than cushioning
Load path: bumpers, ribs and wall thickness
FAQ

1. What a shockproof case is: one load path

An impact enters at the contact point and travels through the bumper, wall, ribs and foam. Each stage rewrites the force-time curve: the peak drops, the duration stretches.

Two numbers judge it: peak acceleration and pulse width.

Thicker walls do not absorb more: stiffness shortens the pulse and lifts the peak, while cushion stroke and density lower it.

Stage	Role	Failure looks like
Bumper	Spreads a point load	Local dent
Ribs	Resist bending	Wall bulges
Foam	Lengthens the pulse	Bottoming out

Shockproof case: black body open, plain lid interior, base foam cut with two round pockets holding discs clamped by white clips, latches raised

2. Impact: g values and drop height

Drop height becomes landing speed: 1.2 m is 4.85 m/s, 1.8 m 5.94 m/s. Once speed is fixed, peak acceleration depends only on stopping distance.

With 25 mm of stroke, a 1.2 m drop peaks near 48 g and 1.8 m near 72 g; doubling the stroke halves both, which is why foam beats wall thickness.

A corner drop is worst: the impact lands on one point, little material deforms, and the peak can double. Test corner, edge, face.

Drop	Speed	25 mm stroke	50 mm stroke
0.8 m	3.96 m/s	about 32 g	about 16 g
1.2 m	4.85 m/s	about 48 g	about 24 g
1.8 m	5.94 m/s	about 72 g	about 36 g

3. Cushioning: foam thickness and density

Softer is not better: too soft bottoms out and the peak rises, too hard never deflects. Peak efficiency sits near 2–3.5 kPa.

EPE at 25–35 kg/m³ rebounds well and costs little; EVA at 60–120 kg/m³ is stiff and clean to cut; PU is efficient but absorbs moisture.

Match thickness to drop: 25–30 mm at 1.2 m, 40–50 mm at 1.8 m, corners half again thicker. Keep 5–10% interference.

Shockproof case: an olive case open on a bench of white pellets, foam pockets holding screwdrivers, pliers, wire bundles and a circuit board

Material	Density	Trait	Use
EPE	25–35 kg/m³	Good rebound	General transit
EVA	60–120 kg/m³	Stiff, clean cut	Precision cavities
PU	30–60 kg/m³	Efficient, moisture sensitive	Heavy loads

4. Restraint: constraint is cheaper than cushioning

Once a load moves more than 2 mm it strikes again on rebound, and the second peak often exceeds the first. Restraint costs far less than foam, so it comes first.

Four means: dividers, preload, straps, plates. Divider walls run 10–15 mm with clearance under 1 mm; preload is a 5–10 mm lid layer; straps anchor on reinforced areas.

A heavy load sits low and central so the case does not rotate; an off-centre one turns, moving the impact from face to corner.

Shockproof case: a dark grey case on a black ribbed mat, scuffed shell, two latches, folding handles front and back, round valve with red ring

5. Load path: bumpers, ribs and wall thickness

The bumper turns a point impact into a 20–30 mm area, dropping local stress by an order of magnitude. Mould it in one piece; bolt-on bumpers loosen in cold.

Ribs run 3–5 mm tall at 40–60 mm spacing; taller ones crack at the root. A 3–4 mm wall is normal for rotomoulded shells; another millimetre adds 15% weight for a few g.

Hinges and latches take load first, so failures start there. Metal pins outlast plastic, clearance stays under 0.2 mm, and the foam-and-load natural frequency should sit above the 3–15 Hz truck band.

Shockproof case: an olive case lying flat, lid lifted to show a black gasket line, two latches and the front handle on one side

Conclusion

A shockproof case is a path: the shell spreads the impact, the foam stretches the time, the lining locks the movement. Thicken one stage and the weakness only moves; the shockproof case works when all three hold.

This article covers container-side specifications and design implications only, not the handling, loading or use of the contents.