What is the minimum test set for hard plastic waterproof cases?

Answer: Two items per layer: thickness and gasket hardness incoming, flash and mould temperature in process, pressure and stacking at final.

Are five thickness readings enough?

Answer: For mid-size boxes yes. Large boxes need nine, one more per 30 cm along the long side, with probes clear of rib roots.

Why is the latch floor 80 N?

Answer: Transport vibration sets it. Below 80 N self-opening rises sharply after a 30-minute sweep from 1 to 200 Hz.

A case holds pressure but leaks on immersion. Whose problem?

Answer: The gasket groove. Local lack of interference still holds pressure while water creeps along the groove floor.

What if the customer supplies only an outline drawing?

Answer: Set an internal standard from these limits, then agree in writing the pressure-drop limit, stacking load and drop height.

Hard Plastic Waterproof Cases: Test Items and Pass-Fail Rules

Quick answer: Acceptance for hard plastic waterproof cases runs in four layers — incoming, in-process, finished goods and pre-shipment — with measurable limits: 3.0±0.3 mm wall, 80–120 N latch force, and no more than 1 kPa drop over 60 seconds at 50 kPa. Lots are judged by AQL, with zero acceptance on critical defects.

Acceptance Inspection Layers
Incoming Wall Thickness Resin and Color
Latches Gaskets and Cycle Life
Water Stack and Drop Judgement
Sampling and Reject Batch Handling
FAQ

1. Acceptance Inspection Layers

A single final inspection is the usual gap in acceptance testing for hard plastic waterproof cases. Water resistance is mostly fixed at moulding: uneven walls pull in stress, an offset latch seat drops closing force to its floor, and a groove cut too deep leaks whatever the gasket. Items run backwards in four layers — 11 incoming, 8 in-process, 9 finished, 4 pre-shipment, 32 in all.

Layer	Items	Basis	Record
Incoming, 11	Melt flow, density, colour, gasket	COA plus retest	Incoming sheet
In-process, 8	Wall, flash, torque, mould temperature	First-off plus patrol	Patrol log
Finished, 9	Pressure, immersion, stacking, drop	Pressure per unit, rest sampled	Final record
Pre-shipment, 4	Appearance, marking, count	Visual	Shipping report

Thresholds move with use: air freight tightens the drop to 0.5 kPa, warehouse turnover allows 1.5 kPa. Verdicts read pass, rework or reject.

2. Incoming Wall Thickness Resin and Color

Thickness precedes appearance. Hard plastic waterproof cases run a 3.0 mm nominal wall at ±0.3 mm, read at five points: side midpoints plus base centre. Under 2.7 mm fails outright, because a thin spot loses impact strength.

Hard plastic waterproof cases: a translucent case open at an angle on a wood bench, dark grey foam with long slots holding slim metal tools

Resin is judged on melt flow and density: the same PP grade sits at 8–12 g/10 min at 230 °C, and a shift over 0.01 g/cm³ sends the masterbatch lot back. Colour passes at ΔE ≤1.5 on D65 and turns major above 2.5.

Item	Point	Pass	Minor	Major
Wall	Five points, sides plus base	3.0±0.3 mm	2.7–2.8 mm	under 2.7 mm
Colour	D65, batch to batch	ΔE ≤1.5	ΔE 1.5–2.5	over 2.5
Gasket	Shore A, median of three	60±5	off by 5–8	off by over 8

3. Latches Gaskets and Cycle Life

Latches are the only load-bearing part a person operates, so the reading is closing force, not feel. Hard plastic waterproof cases hold 80–120 N: under 80 N a latch opens on a vibration table, over 120 N it cannot be closed in one gloved motion.

Life is 5,000 cycles with no more than 15% force loss; three whitened latch-seat roots stop the line for a mould check. Gaskets run Shore A 60±5, recovering 90% at 30% compression, seated in a groove with 0.3 mm interference and four readings within 0.2 mm.

4. Water Stack and Drop Judgement

Judgement for hard plastic waterproof cases runs water, load, drop. Inflate to 50 kPa, hold 60 seconds, accept a 1 kPa drop; then one metre of water for 30 minutes with no trace inside or in the groove.

Hard plastic waterproof cases: a translucent case upright on a workshop bench, lid facing out with screwdrivers in foam slots, tools beside it

Stacking is 300 kg for 24 hours, with lid deflection over 2 mm failing and base corners checked. Drop is 1.2 m onto concrete, corners and latches watched, then a second pressure test. Climate is three cycles of 4 hours at −20 °C and +60 °C with 2 hours of recovery.

5. Sampling and Reject Batch Handling

Lot judgement for hard plastic waterproof cases follows GB/T 2828.1 at level II. At 501–1200 units the sample is 80: critical zero-accept, major at AQL 1.0 with acceptance 2 and rejection 3, minor at AQL 2.5 with 5 and 6.

Class	Examples	AQL	Verdict at n=80
Critical	Latch fracture, missing gasket	0	One unit rejects the lot
Major	Excess pressure drop, wall under 2.7 mm	1.0	Accept 2, reject at 3
Minor	ΔE 1.5–2.5, flash 0.2–0.4 mm	2.5	Accept 5, reject at 6

Reworked lots are re-inspected at the original sample size. Concessions take three signatures, three retained samples held 12 months.

Conclusion

Acceptance is not a checklist but a system of layered limits and records: incoming holds thickness, in-process holds flash and mould temperature, finished goods hold pressure, pre-shipment holds marking. Give limits real numbers and verdicts real actions, and disputes have somewhere to land. Whether a lot of hard plastic waterproof cases ships comes down to whether those four layers reconcile.

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.