How many drops must an impact-resistant protective case survive?

Answer: The military transit drop runs 26 over 8 corners, 12 edges and 6 faces; ISTA folds drops into a longer sequence.

At one height, which is harder, empty or loaded?

Answer: Empty. With no mass on the cushion the shell takes everything and corners split first.

Why test a cold drop separately?

Answer: Plastic embrittles at minus 20 and may lose half its impact strength.

Does the seal still count after a drop?

Answer: Only after a recheck. A 2 mm corner distortion can leave the gasket uncompressed.

Can limits be relaxed?

Answer: Appearance can, if the contract names it. Corner distortion and latch action decide seal and closure.

Impact-Resistant Protective Case Standards: Tests and Limits

Quick answer: Judge an impact-resistant protective case by shape, latch action and seal contact after the drop, not by wall thickness. Attitude, energy and limit make the sheet.

Acceptance Levels for an Impact-Resistant Protective Case
Turning Impact Energy into Drop Height
Judging Corners, Edges and Faces
How the Two Drop Standards Differ
Preconditioning, Recheck and Pass Limits
FAQ

1. Acceptance Levels for an Impact-Resistant Protective Case

Acceptance turns one fall into three facts: which attitude hit the floor, how much energy it carried, which dimensions stayed inside the limit. Leave one out and the report falls back on no visible damage.

Three levels, none replacing another. A type test uses three samples and allows zero failures. A first-article check records readings from a new mould. A batch sample follows AQL 2.5 for appearance and latch action.

Level	Samples	Verdict
Type test	3	All pass, zero failures
First article	1	Key items pass
Batch sample	AQL 2.5	Appearance and latch

An impact-resistant protective case is accepted empty and loaded too. An empty shell has no mass on the cushion, so a corner splits first; a loaded one carries more energy but the insert absorbs part.

2. Turning Impact Energy into Drop Height

Height is the visible half; what breaks a shell is kinetic energy at contact, mass times gravity times height. One impact-resistant protective case at 12 kg and at 25 kg carries more than twice the energy from one height, yet one limit is often written for both.

Impact-Resistant Protective Case: olive green closed case angled on a green backdrop, three lid ribs, two matched latches at the front rim, recessed folding handle

Start with rated load: 1.0 times for most industrial buyers, 1.2 for aviation. Ballast sits at the geometric centre; once it shifts, a face impact becomes a corner.

Test mass	Drop height	Impact energy
12 kg	0.76 m	about 89 J
18 kg	1.22 m	about 215 J
25 kg	1.50 m	about 368 J

ISTA steps by weight: 76 cm below 9 kg, 61 cm to 18 kg, 46 cm to 27 kg, 38 cm to 45 kg. Military programmes fix 1.22 m, or 48 inches, whatever the mass.

3. Judging Corners, Edges and Faces

A corner drop is the hardest attitude: the blow lands on one vertex, few millimetres deform, and the peak can reach twice the face value.

Faces are judged on denting: a centre dent within 3 mm, no through crack, no whitening at rib roots. Edges on crack length: up to 15 mm without crossing the wall passes; a through crack drops local wall from 4.5 mm to 3 mm.

Corners turn reports vague. Measure distortion within 2 mm, no split longer than 10 mm at the radius, and a latch closing one-handed with lid gap under 1.5 mm.

4. How the Two Drop Standards Differ

ISTA serves packaging, MIL-STD-810 serves equipment. The first asks whether goods arrive intact, the second whether hardware still works. Export work follows ISTA; police and aviation follow Method 516.7, numbered 516.8 in revision H.

Impact-Resistant Protective Case: olive green closed case facing the camera on pale grey floor, two black latches on the front, side folding handle at right

Sequence differs. ISTA runs vibration, incline impact, rotational edge drop, then free drop. The military transit drop runs 26 drops over 8 corners, 12 edges and 6 faces, checking appearance and function after each. Steel gives a short contact and a high peak; plywood reads one or two tenths lower.

5. Preconditioning, Recheck and Pass Limits

Shells are usually moulded in high-density polyethylene, whose impact strength moves fast with temperature. At minus 20 a falling-weight test may read half the room value, so preconditioning comes first: 4 hours at minus 20, 4 hours at plus 60, 24 hours at 95 percent humidity.

Recheck runs appearance, dimensions, latch action, then seal. Air decay is quickest: charge to 20 kPa, hold 60 seconds, pass at 0.5 kPa loss or less.

Item	Method	Pass limit
Face dent	Depth gauge	3 mm or less
Edge crack	5x magnifier	15 mm or less, not through
Corner distortion	Plate and feeler gauge	2 mm or less
Lid gap	Feeler gauge	1.5 mm or less
Latch action	Three cycles	All three close
Air decay	20 kPa, 60 seconds	0.5 kPa or less

Write limits as absolutes, never as no visible damage: another operator, another rig, the same number.

Conclusion

An impact-resistant protective case is accepted on three sheets: energy against height, corner, edge and face limits, and the recheck after preconditioning. Together they turn one fall into a number. Absolute limits are what make an impact-resistant protective case defensible.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.