Should an Equipment Case drawing give the cavity at the mouth or the floor?

Answer: Both. The mouth decides entry, the floor where hardware lands; the draft connects them.

Does a 3.8 mm lid raise the rating?

Answer: No. Tiers follow rib height and spacing, and the heavier lid only adds 0.4 kg.

Can an IP67 Equipment Case stay submerged?

Answer: No. Thirty minutes at 1 m is the limit; a long soak sets the gasket.

Is a 4 mm divider rib too thin?

Answer: At 40 mm depth it is fine. Past 60 mm use 5 mm ribs or two layers.

Does a cutout void the ingress rating?

Answer: Unless it is closed properly. Fit the stiffener and seal, then repeat the test.

Equipment Case Specifications: Size, Wall Thickness and Load

Quick answer: An Equipment Case is specified from the cavity outwards: subtract the foam, add wall, lid depth and bumpers, then check the lid ribs against a full stack. A figure written before that chain closes is paid for twice.

How an Equipment Case Size Chain Closes
Foam Dividers and Usable Space
Wall, Weight and Stack Load
Ingress Rating and Test Recipe
Cutouts, Stiffeners, Grounding, Shielding
FAQ

1. How an Equipment Case Size Chain Closes

The outside is fixed before drawing: a 1200 mm pallet takes two 620 mm cases with 40 mm for hands, a 1500 mm shelf four 230 mm tiers.

The cavity is where guesswork enters. On an Equipment Case, a 3.2 mm wall, a 55 mm lid and one degree of draft give 612×432 mm at the mouth but 605×425 mm at the floor, and the 8 mm rim groove leaves 560×380×195 mm usable.

Layer	Measured	Mid-size	Usual error
Outside	Over latches and bumpers	620×440×230 mm	8 mm latch proud
Mouth	Wall to wall at rim	612×432×195 mm	Floor only
Usable	Cavity minus foam	530×350×155 mm	Ribs not deducted

One degree costs 3.5 mm per side at 195 mm depth, silently eating a module's clearance.

2. Foam Dividers and Usable Space

A 20 mm base layer and a 30 mm lid layer are common, the lid foam pressing the top face at 5% compression. Stiff EVA at 90 kg/m³ takes a 3% set.

Equipment Case: a black case open forty five degrees, grey EVA with stepped pockets left and plain foam right, two latches and a vent

A 4 mm rib in a 40 mm pocket takes 2 mm per side, so 98 mm holds a 96 mm module. At 3 mm the divider bows 1.5 mm in a year; at 5 mm the body goes up a size.

Die cutting needs 0.3 mm offset: EVA springs back within 24 hours, and a nominal 98 mm pocket measures 97.6 to 97.8 mm. Past 40 mm depth, split the block at 45 degrees.

3. Wall, Weight and Stack Load

A rating needs a load distribution. The 45 kg rating of an Equipment Case is uniform over the 0.21 m² floor, 2.1 kPa; the same load on one 80×80 mm pad reaches 69 kPa.

Outside	Wall	Weight	Uniform load	Tiers
460×350×180 mm	2.8 mm	4.2 kg	25 kg	5
620×440×230 mm	3.2 mm	6.8 kg	45 kg	4
780×560×300 mm	3.6 mm	11.5 kg	70 kg	3

Four high puts 3 × 45 = 135 kg on the lowest lid, doubled to 270 kg, or 1.45 kPa on 530×350 mm; 6 mm ribs at 90 mm centres deflect 1.3 mm under 500 N.

4. Ingress Rating and Test Recipe

IP67 is a recipe, not a label: 1 m of water, case and water within 5 °C, 30 minutes, then inspect. A warm case in cold water pulls a vacuum through the weakest seam: it passes in a bath and fails after a truck ride.

Equipment Case: a black closed case angled on a dark background, crossed ribs, a round pressure vent between two wide toothed latches

IP65 is a jet instead: 6.3 mm nozzle, 12.5 L/min, 3 m, 3 minutes. Where water is impractical, charge to 2 kPa, hold 60 s, accept 0.3 kPa decay. A 60 shore gasket of 6×4 mm runs at 25% compression; the vent cracks at 8 kPa.

5. Cutouts, Stiffeners, Grounding, Shielding

Cutouts decide whether hardware fits. An M22 gland wants 22.5 mm plus 0.2 over zero; a rectangular connector takes the flange plus 0.3 mm, drilled from the connector drawing. Keep 25 mm clear of corner radii.

Interface	Cutout	Stiffener	Seal
Cable gland	22.5 mm round	4 mm 6061	22×2.4 mm O-ring
Rectangular plug	Flange plus 0.3 mm	5 mm plate	Conductive gasket
Vent port	40 mm perforated	3 mm stainless	Breathable membrane

Four millimetre 6061 with six M4 rivet nuts at 60 mm centres restores the lost stiffness; torque diagonally in two passes to 2.5 N·m.

Grounding: an M6 stud bonded to the stiffener with 16 mm² braid, 0.1 Ω or less. Shielding depends on pitch: 40 dB at 1 GHz at 60 mm screw spacing, 28 dB at 100 mm, where the gap acts as a slot antenna.

Conclusion

Usable space sets the cavity, draft sets the outside, load sets the tiers, and the tiers return to the lid ribs. Walk it once and the Equipment Case holds what the sheet promises.

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.