How many items make a bespoke plastic protective case spec complete?

Answer: Three groups: dimensions, structure and performance, from cavity figures to stack sag.

Why not one ±2 mm tolerance for the cavity?

Answer: It suits a foam-lined case and fails one holding hardware, where each millimetre changes how a device seats.

Can the customer's stack height be written as asked?

Answer: Work backwards: convert layers into a load, then check whether the lid ribs hold 24-hour sag within 1.5 mm. If not, thicken the lid.

How is the air test run on a valved case?

Answer: Plug the valve before pressurising, or air escapes. Test it alone at 3 to 5 kPa to open, then 10 kPa held 30 seconds in reverse.

Can T1 samples ship as production?

Answer: No. Hand-tool samples can pass on dimensions while wall distribution and stress differ. Production needs the T2 run.

Bespoke Plastic Protective Case Specs: Size, Wall, Load

Quick answer: A bespoke plastic protective case is pinned down by three sets of numbers: the outside-to-cavity gap, wall thickness by zone, and the static load implied by stack height. Start at ±1.0 mm cavity tolerance, 3.0 mm sides over a 3.5 mm base, and 150 kg at five high.

How a Bespoke Plastic Protective Case Spec Is Sized
Wall Zones That Must Be Thickened
Load Rating, Stacking and Layer Limits
Latch, Gasket and Pressure Valve Matching
Tolerances, Samples and Acceptance
FAQ

1. How a Bespoke Plastic Protective Case Spec Is Sized

A bespoke plastic protective case carries three dimension sets, not one: outside, cavity and usable cavity. The outside sets transport and stacking, the cavity sets what fits.

State them in that order with foam thickness. A 600 × 450 × 220 mm body with 20 mm foam all round leaves a cavity near 540 × 390 × 185 mm; take 25 mm off the base and 15 mm off the lid and usable height is 145 mm.

Dimension set	What to state	On a 600 × 450 × 220 mm body	Decided by
Outside	Length, width, height with corners	600 × 450 × 220 mm	Tool size, stacking
Cavity	Floor length, width, depth to lid foam	540 × 390 × 185 mm	Wall and rib height
Usable	Clear space after all foam	500 × 350 × 145 mm	Foam plan and cuts

2. Wall Zones That Must Be Thickened

One wall number on a bespoke plastic protective case means the moulder builds to the thinnest point. Write zones instead: 3.0 mm sides, 3.5 mm base, 2.8 mm lid, 4.5 mm at corners and latch bosses.

Bespoke plastic protective case: closed grey case on a worn wooden bench, two latches and a folding handle, timber workshop with blue and black cases

Zoned walls hold the load path for a tenth of the weight that thickening everything would add, which takes the body from 3.4 kg to 4.3 kg.

Thicken where force travels: 120 mm either side of the handle, each latch boss root, the hinge seats, the base corners. On a 650-tonne press, walls under 2.2 mm short-shot over a 300 mm flow.

3. Load Rating, Stacking and Layer Limits

Load needs three figures: static, a full case at rest; dynamic, the transport peak at 1.5 to 2 times static; stacking, upper cases on a lower lid. A typical sheet reads 45 kg, 90 kg and five high at 30 kg each.

Layer limits come from the long-term sag of the bottom lid. Past 2 mm of base sag or 1.5 mm of lid sag after 24 hours loaded, the second layer tilts.

Every figure carries its test conditions: 45 kg for 24 hours at ambient is not 45 °C for 72 hours.

4. Latch, Gasket and Pressure Valve Matching

Latch count follows length: two under 600 mm, three from 600 to 900 mm, four above 900 mm, spaced no more than 250 mm. Wider spacing bows the lid gap, the gasket misses its compression, and the air test finds it.

Bespoke plastic protective case: dark grey case strapped on a steel roller conveyor, vertical side ribs, roller shutter and black flight cases behind

Compression and hardness belong on the sheet: an O-profile returns best at 25 to 30 percent of its diameter, near Shore A 55, with 0.8 mm lid gap flatness.

Across a 40 °C swing the differential reaches 6 to 8 kPa; without a valve that force lands on the latches and the lid jumps open. Specify 3 to 5 kPa to open and 0.5 litres per minute.

5. Tolerances, Samples and Acceptance

Split tolerances by location: cavity length and width ±1.0 mm, depth ±0.8 mm, diagonal difference within 1.2 mm, lid gap 0.6 to 1.0 mm. A twisted bespoke plastic protective case shows in the diagonal before it leaks.

Sampling runs in two steps. T1 is three pieces, dimensions and assembly only. T2 takes one through a 1.2 m drop on six faces, three edges and a corner after 4 hours at −20 °C, and another through 24 hours of loaded stacking.

Item	Limit	Sampling
Cavity length, width	±1.0 mm	5 per lot, all measured
Diagonal difference	Within 1.2 mm	5 per lot
Loaded stacking	24 hours, base sag within 2 mm	1 per lot

Conclusion

A specification turns wishes into measurable numbers: three dimension sets fix the space, zoned walls distribute weight, load figures set the boundary, latch and gasket keep the lid closed. Compress the five sections into one sheet and the bespoke plastic protective case is finally specified.

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.