Does a custom protective case above 600 mm always need castors?

Answer: No. Below 35 kg loaded and 20 m of travel, two people move it faster and the castor bay costs 18 mm of cavity height.

Is an 8 mm wall safer than 6.5 mm?

Answer: Not by itself. On a custom protective case, past 9 mm the cooling difference shows as wavy sinks and empty weight passes 30 kg.

Should stacking follow warehouse height or load?

Answer: Both, and the lower figure wins. Three layers leave the bottom unit at 104 kg, but a 2.4 m ceiling allows two.

Do more latches make the case safer?

Answer: No. Six latches at 480 N each demand real force, and one-handed closing rarely seats them.

Should cavity tolerances be symmetrical?

Answer: Write them unilateral. Foam can grow 3 mm to fill a loose cavity; a wall cannot shrink back.

Custom protective case specs: size, wall thickness and load

Quick answer: Size a custom protective case by how it moves, not by a catalogue. Past a 600 mm cavity the shell is rotomolded at 5.0 to 8.0 mm, stacking is proven at three layers over 24 hours, and wheeled versions rate the castors separately.

Sizing a custom protective case from the carry method
Converting outer dimensions into usable cavity space
Wall thickness tiers for rotomolded shells
Load, stacking and corner reinforcement
Latch count and gasket compression
FAQ

1. Sizing a custom protective case from the carry method

The first line of the sheet answers who lifts the box. Past a 600 mm cavity one hand is impossible, leaving two carriers, four carriers, or a wheeled shell towed behind.

A custom protective case does not scale evenly from inside out: grip relief, a castor bay or forklift apertures all sit outside the cavity.

Carry tier	Outer L×W×H	Cavity	Side wall	Empty	Loaded
Two-person	880×520×360 mm	800×440×290 mm	5.0 mm	11.2 kg	32 kg
Wheeled	1180×560×420 mm	1100×480×350 mm	6.5 mm	16.8 kg	52 kg
Four-person, forklift	1480×620×480 mm	1400×540×410 mm	8.0 mm	24.6 kg	78 kg

The step is not decorative: a 52 kg wheeled unit resists turn side load through its own walls, while a 78 kg unit lands as vehicle mass.

2. Converting outer dimensions into usable cavity space

Buyers quote the cavity; moulders build the outside. On the wheeled tier, 1180 minus 1100 divided by two leaves 40 mm per side, consumed by six features.

Custom protective case: black shell open on pale grey, yellow trim and four latches, round relief valve on the front face, foam holding an instrument

Allowance	Per side	Note
Side wall	6.5 mm	Lowest of four readings
Vertical rib	12 mm	140 mm pitch, inward
Corner radius	8 mm	Space lost to an R25 corner
Gasket groove	6 mm	Paired with a 9 mm cord
Lid step	2.5 mm	Stops edge bite
Moulding and assembly	5.0 mm	Shrinkage plus foam compression
Total	40 mm	1180 minus 1100, halved

Length and width split this way; height does not. The wheeled tier runs a 350 mm cavity in a 420 mm shell, with 18 mm of the 70 mm gap lost to the castor bay.

3. Wall thickness tiers for rotomolded shells

Past 600 mm a custom protective case is rotomolded, not injection moulded. Aluminium tooling keeps cost down but leaves thickness to powder charge and oven time, so ±0.2 mm becomes ±0.8 mm.

The window sits beside the wall figure: 275 °C oven, 26 minutes, a 4:1 dual-axis ratio, 12 minutes of forced cooling. Ten degrees cooler and the powder never fuses.

Thickness is written per zone: 6.5 mm side walls, 8.0 mm base for abrasion, 10 mm corners, 12 mm hinge bosses. Corners take the first contact in a drop.

4. Load, stacking and corner reinforcement

For a custom protective case, load splits into static weight and towing fatigue.

Custom protective case: yellow corner in close view, one wide latch clamping the parting line between lid and base, four vertical ribs below it

A loaded wheeled unit at 52 kg stacks three high, so the bottom shell carries 104 kg; a 1.5 factor lifts the design value to 160 kg, held 24 hours against 2.0 mm deflection. Four 75 mm castors rate 45 kg each.

Ribs matter during towing, when a shell dragged over a threshold loads corners in turn. Drops run at 1.2 m on six faces, three edges and one corner; at -30 °C the height falls to 0.9 m.

5. Latch count and gasket compression

Latch count follows cavity length: two under 800 mm, four at 1100 mm, six at 1400 mm, spaced 240 to 280 mm. Past 300 mm the gasket lifts the lid between latches.

A 9 mm cord in a 6 mm groove lands at 30 percent compression. Below 25 percent it leaks; above 35 percent the lid needs body weight.

Tier	Latches	Holding force each	Gasket cord	Compression	Rating
Two-person	2	320 N	7 mm	28%	IP65
Wheeled	4	420 N	9 mm	30%	IP67
Four-person, forklift	6	480 N	11 mm	32%	IP67

Hinge pins are 8 mm 304 stainless, cleared at 480 hours of salt spray. The gasket is EPDM, rated -30 °C to 60 °C.

Conclusion

The chain runs backwards from handling: tier, shell, cavity, wall. A custom protective case is calculated and proven, never picked from a page.

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.