Which comes first for a Communication Equipment Case, cavity or envelope?

Answer: The cavity, from device outline plus rail clearance plus bend radius; the envelope sums wall, rib and feet.

Is 3.5 mm enough wall?

Answer: Judge by handling weight. At 3.5 mm one person carries it; 4.5 mm needs two, while the dent only falls to 0.7 mm.

How many stacking layers should be claimed?

Answer: Three at 23 C, two at 40 C, one at 55 C, stating whether it covers bare cases or a pallet.

Can every tolerance be plus or minus 0.5 mm?

Answer: No. Shrinkage over 700 mm runs 1.0 to 1.6 mm, so a blanket 0.5 mm scraps good parts.

Is a higher ingress rating always better?

Answer: No. IP67 needs six latches and 110 N of opening force; for weekly servicing, IP65 fits better.

Communication Equipment Case Specifications: Size, Wall and Load

Quick answer: A Communication Equipment Case is specified from the cavity outward: fix internal size from the device plus rail and cable clearance, back-calculate wall thickness from the weight two people can lift, then discount layers by storage temperature.

Building the Size Chain for a Communication Equipment Case
Wall Thickness Against Total Case Weight
Load Ratings and Stacking Layers
Tolerances on Mating Surfaces
Temperature and Ingress Rating Allowances
FAQ

1. Building the Size Chain for a Communication Equipment Case

A Communication Equipment Case is drawn from the cavity outward. A 19-inch 4U switch is 483 mm wide and 350 mm deep: 12 mm slider clearance per side gives 520 mm width, 60 mm at the rear covers bend radius and 25 mm at the front clears the panel, so depth is 380 mm.

The cavity is the only anchor; add 3.5 mm walls, a 10 mm lid rib, 15 mm feet and 0.5 degrees of draft, and the envelope is 742 x 562 x 424 mm.

Chain element	Value	Source	Marked as
Cavity	560 x 520 x 380 mm	Device plus clearance	Basic, toleranced
Wall	3.5 mm	Back-calculated	Critical
Envelope	742 x 562 x 424 mm	Sum of the above	Bracketed

Reverse the order and it fails: a 760 x 580 x 430 mm envelope leaves a 535 x 480 x 355 mm cavity, so the harness bends against the wall.

2. Wall Thickness Against Total Case Weight

The conversion is one multiplication: 2.05 sq m of shell is 20500 sq cm, so 3.5 mm gives 7175 cubic cm and 6.7 kg at 0.94 g per cubic cm. Hinges, latches, a valve and corner caps add 2.4 kg, making 9.1 kg.

Communication Equipment Case: blue racking mid-shop, a red gantry hook overhead, steel moulds flat on the floor, a green vertical machine at right

Thickness is capped by handling, not strength. One person carries 12 kg, two carry 25 kg, and every extra 0.5 mm adds 0.96 kg; 3.5 to 5.0 mm adds 2.9 kg and crosses that line.

Wall	Weight	Dent, 1 m ball	Handling
3.5 mm	9.1 kg	1.5 mm	One person
4.5 mm	11.0 kg	0.7 mm	Two people

Specify 3.5 plus or minus 0.3 mm; a 0.3 mm spread per cycle is normal, and 3.0 mm at the thinnest point must still pass the falling ball test.

3. Load Ratings and Stacking Layers

Two ratings get confused. Static top load is uniform load on the lid: 90 kg for 24 hours at 23 C with 3.5 mm walls, sagging under 2 mm. Stacking load is judged by permanent set, so it sits a grade lower at 60 kg.

Ambient	Layers	Top load	Criterion
23 C	3	90 kg	24 h sag 2 mm
40 C	2	60 kg	48 h sag 3 mm
55 C	Single	45 kg	48 h set 3 mm

Temperature is the sharpest discount: polyethylene loses about 25 percent of its modulus at 40 C, dropping three layers to two. Load 48 hours, unload, wait an hour, measure set rather than rebound. Corner caps and base skids carry force down the posts; side-wall bearing shells bulge at the second layer.

4. Tolerances on Mating Surfaces

Fit dimensions cover lid closure, assembly dimensions cover hinge, latch and rail holes, form dimensions cover envelope and flatness; each needs its own gauge.

Communication Equipment Case: yellow gantry beam marked 2.8t, a white moulding machine behind, cast blower wheels on a yellow trolley, open carton in front

Over 700 mm the moulding shrinks 1.0 to 1.6 mm, so plus or minus 0.3 mm scraps the batch. Cavity 1.5 mm, envelope 1.2 mm and wall 0.3 mm work. A 0.8 mm lid gap is 30 percent gasket compression; below 0.2 mm the latches bind.

5. Temperature and Ingress Rating Allowances

Storage is minus 30 C to 55 C, operating minus 20 C to 45 C. Six hours at minus 30 C then a 1.2 m drop must leave corners uncracked, which holds regrind below 15 percent.

An ingress rating must become structure. IP65 needs 30 percent gasket compression and four latches; IP67 demands 1 m immersion for 30 minutes, so compression goes to 35 percent and latches to six, lifting opening force from 60 N to 110 N.

A sealed case sheds heat only through its walls: 100 W at 25 C runs 15 C hotter inside, so IP67 needs a conduction path.

Conclusion

Cavity sets the datum, wall sets handling, load sets layers, tolerance sets inspection, ingress rating sets structure; change one and four need rechecking. Written this way, the Communication Equipment Case specification closes without argument.

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.