Our plastic waterproof cigarette case is IP67, so why test immersion?

Answer: IP67 grades the enclosure, and the report sample may not be your batch. A 300 mm, 30-minute immersion catches a missing gasket.

Is vacuum hold not the same as immersion?

Answer: No. Immersion shows whether water enters; vacuum shows whether the sealing face has a gap, separating a flange leak from a valve leak.

Answer: Workable, not absolute. Thirteen from 1,200 units returns the batch on one Class A defect; above a 2% rate, go to 32.

Retest after changing gasket supplier?

Answer: Yes. Five points of hardness shift compression by three points, so vacuum and immersion repeat.

Plastic Waterproof Cigarette Case: Testing at 47 °C on the Dock

Quick answer: Acceptance of a plastic waterproof cigarette case is not a sentence about being waterproof. Turn it into five dock readings — wall, vacuum, immersion, latch pull, hinge cycles — then route failures by class.

What a plastic waterproof cigarette case must survive first
Where the pass line is written
Four field checks and their readings
Handling failures: repair, downgrade, reject
Three columns on the acceptance sheet
FAQ

1. What a plastic waterproof cigarette case must survive first

A July afternoon, a box van at the dock: 47 °C mid-bed, 82% relative humidity, cartons three tiers high. The first thing to fail on a plastic waterproof cigarette case here is not the seal. It is the lid.

Heat releases moulded-in stress; the lid sags within four hours, and 0.8 mm stops the gasket being squeezed. Three tiers put about 9 kg on the bottom case, and a thin wall bulges, pulling the catch out of engagement.

Condition	Reading	First failure
Closed-van heat	47 °C, 82% RH, 4 h	Lid sag, soft gasket
Three-tier stack	9 kg on bottom unit	Wall bulge, latch offset
Dock drop	1.1 m	Corner crack, loose hinge boss

Three conditions, three failures, one line on the sheet.

What is verified is a reading, not a feel.

2. Where the pass line is written

On the drawing, water resistance is three measurable lines: wall, gasket compression, latch retention. Tolerances come from the drawing, methods from the standard, the gap from the sheet.

Plastic waterproof cigarette case: grey-blue open body with internal dividers, red and grey packs in rows, a coiled grey cable at right

First line, thickness: 1.8 mm body, 2.0 mm lid, plus or minus 0.1 mm, five ultrasonic points, minimum below 1.7 mm fails.

Second, the sealing face. A 3.5 mm silicone cord must compress 25% to 30%; less and water passes, more and it takes a set and loses rebound by the third open.

Third, latch retention: two over-centre catches holding at least 150 N, pulled with a gauge and read at peak.

Item	Pass value	Method
Body wall	1.7 mm minimum	Ultrasonic, five points
Gasket compression	25% to 30%	Feeler gauge
Vacuum hold	-30 kPa, 90 s, drop under 1.5 kPa	Gauge, stopwatch
Immersion	300 mm, 30 min, no trace	Tank, balance
Latch retention	150 N minimum	Force gauge

Every row needs a number, not two words on a form.

3. Four field checks and their readings

No laboratory on a dock: a folding table, a tank, twenty minutes per case.

Thickness: probe the middle and four corners, keep the lowest of five; under 1.7 mm the unit fails.
Vacuum: latch the lid, draw to -30 kPa, time 90 seconds; a drop past 1.5 kPa means a gap on the sealing face.
Immersion: sink the weighted case to 300 mm for 30 minutes, dry, open, look for traces; a 2 g gain means ingress.
Latch pull: pull to 150 N, hold 5 seconds; a catch that springs back has failed.

Two items come from records: hinge alignment after 3,000 cycles, and corner whitening.

Hinges are overlooked more often than latches.

4. Handling failures: repair, downgrade, reject

A failure is not a return. Grade it, then pick the route: three classes, one disposal path each, written into the contract.

Plastic waterproof cigarette case: close view of a brick-red open body, thickened rim with a closure groove, matching inner wall

Class A is critical: water inside after immersion, a catch releasing at 150 N, a cracked body. Nothing ships.

Class B is major: wall under 1.7 mm, vacuum drop past 1.5 kPa, compression below 25%. Repair the cord or catch, then screen every unit.

Class C is minor: colour, flash, print offset. Accept with a credit or downgrade at seventy percent.

Sampling is fixed in advance: on a 1,200-piece batch draw 13 units; one Class A returns the batch, three Class B tighten to 32, where two more also return it.

Class	Finding	Disposal
A critical	Ingress, latch release, crack	Batch returned
B major	Wall 1.65 mm, drop 2 kPa	Repair, full screen
C minor	Colour, flash, print offset	Credit or downgrade

5. Three columns on the acceptance sheet

The sheet needs three columns: item, pass value, evidence. Miss one and it fails in a dispute.

Name the item as the drawing does: body wall thickness, not how thick it feels. Give the value a unit: -30 kPa for 90 seconds. Evidence is a photograph and a raw reading, such as the inner wall as the lid opens.

Retest rules are usually left out. A good first article does not make a good batch: tool wear pulls the wall down after the two-thousandth shot, and a new cord lot shifts compression. Write four triggers into the sheet: material change, mould change, a line stop past seven days, or two consecutive batches with Class B defects. Each forces a new first article. Thickness, vacuum and latch are mandatory; immersion and salt spray may cite the previous report if dated after the last material change. Put those triggers on paper and the sheet becomes a rule for every later batch of the plastic waterproof cigarette case.

Conclusion

Acceptance of a plastic waterproof cigarette case turns one adjective into five numbers: wall, vacuum, immersion, latch pull, hinge cycles. Put the pass lines on drawing and sheet, split failures into three classes, and repair, downgrade and return each find their place. Twenty minutes of readings before loading costs far less than a batch of rework, which is the real value of a plastic waterproof cigarette case test.

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.