How many units should travel case production sample from 1800?

Answer: 125 under GB/T 2828.1 level II. Major defects run at AQL 1.5, accepting 5 and rejecting 6; minor defects at AQL 2.5, accepting 7 and rejecting 8.

Can an 8 km run stand in for 32 km?

Answer: No. Eight kilometres wears the tread, while the crack at the housing root needs 20 km to appear. Compress the clock, never the distance.

Is a 2 mm cavity tolerance too loose?

Answer: It suits this band. Over a 520 mm span, moulding shrinkage alone moves 0.6 mm; at 1 mm the pass rate drops to about 70%.

How much trolley play fails a travel case production batch?

Answer: More than 2 mm at the top after 3000 cycles, which feels like a finger's width of side play.

How long should travel case production keep records?

Answer: Three years, reaching the lot number, sample size, measured values and the name of whoever signed.

A 1800-Unit Return: Rethinking Travel Case Production Sign-Off

Quick answer: That batch came back because acceptance was thin, not because the mould was wrong: three units sampled, one dimension measured, fatigue never run. Lift the sample to 125, write the verdict in millimetres and cycles, and classify the defects.

How travel case production sign-off failed on an 1800-unit batch
Dimensions and appearance: three gauges decide
Travel and drop: two separate lines
Handles and trolleys: the fatigue curve
Disposition: rework, concession, rejection
FAQ

1. How travel case production sign-off failed on an 1800-unit batch

In November, 1800 cases shipped north and 214 came back within 14 days: 96 cracked wheel housings, 71 loose trolleys, 47 burst handle seams. All three items had been ticked as passed.

The outgoing check was visual only: the travel rig pulled 3 units from 200, the trolley rig 2 units twice a week. That proves the machine turns, not that the lot is sound.

Travel case production has to state its verdict as a number. "Moves freely" gives two inspectors two answers; 1.9 mm, 3000 cycles and 2 mm give one.

Item	Field method	Verdict line
Cavity	Tape, 3 points per axis	520 mm nominal, within 2 mm
Shell wall	Ultrasonic, 5 points	1.9 mm nominal, 1.7 mm floor
Wheel travel	23 kg payload, 32 km	Tread loss 1.5 mm or less
Trolley	3000 cycles, 300 N side	Top play 2 mm or less

Sampling follows GB/T 2828.1 level II, where 1800 draws 125. Major defects at AQL 1.5 accept 5 and reject 6; minor at AQL 2.5 accept 7 and reject 8. Eight defectives inside 125 and the lot stays outside.

Travel case production then gives three failures their own lines. The corner wall drops from 1.9 mm to 1.6 mm and keeps the stress; a burr inside the tube never shows up in a 3-unit pull; stitch density slides from 8 per 25 mm to 6.

2. Dimensions and appearance: three gauges decide

Travel case production cannot judge size by eye. The cavity is 520 by 360 by 240 mm, taped at 3 points per axis, and any point past 2 mm fails. Keep the diagonal spread under 3 mm, or the frame loads one side and latch life halves.

Travel Case Production: grey plastic case side latch in close-up, square same-colour catch over the lid seam, pebbled texture and shallow scratches

A 1.9 mm wall with a 1.7 mm floor needs an ultrasonic gauge at 5 points; a 1.6 mm corner cracks at -20℃ and the crack runs 40 mm along a rib.

Colour reads ΔE 1.5 within a lot, 2.0 across lots. A 0.3 mm feeler catches the parting line; the zip-to-frame gap stays at 0.5 mm, or a 23 kg load bows the frame.

3. Travel and drop: two separate lines

Travel is 32 km of small repeated shocks; drop is one peak event. A single rig cannot read both.

Test	Sequence	Verdict
Travel	23 kg at 4 km/h over 1000 obstacle bars	32 km clean, tread loss 1.5 mm
Drop	1.2 m, 6 faces 3 edges 1 corner	No through crack, latch shut
Cold drop	-20℃ for 4 hours, then 1.2 m	Crack 5 mm or shorter

Travel case production runs 32 km, not 8: eight kilometres only skins the tread, and the housing crack starts after 20 km. Torque the axle nut to 1.2 N·m. Drop from 1.2 m, hand-carried height, and release a cold case within 30 seconds of the chamber.

4. Handles and trolleys: the fatigue curve

A trolley is judged on a curve. After 3000 cycles the top play grows from 0.8 mm to 1.6 mm; at 2.4 mm the wall is thin and 500 more cycles will rattle.

Travel Case Production: a silver hard case open on a wooden bench, black egg-crate foam across the lid, folded clothes and cables beside it

Run 3000 cycles at 30 per minute with a 400 mm stroke and 300 N hanging at the top, mimicking a turn with a loaded case. Handles take 500 N for 60 seconds, then 3000 lifts at 8 stitches per 25 mm in 210D polyester; at 6 stitches the static test passes and the lifts burst by 2000.

Temperature belongs in the line. At 60℃ the same 500 N leaves 3 mm of set instead of 1.2 mm, so write the limit against the hot result.

5. Disposition: rework, concession, rejection

Class	Examples	Action
Critical	Latch failure, trolley pull-out	Quarantine, inspect every unit
Major	Cavity out of tolerance, wall under 1.7 mm	Rework or reject the lot
Minor	0.3 mm parting line, light scuff	Concession or down-grade

Travel case production reworks at about 38 yuan a unit, while returning a lot costs 96 yuan a unit with freight and storage. Critical defects sit outside that arithmetic.

Concessions need written consent, a capped quantity and a separate lot number, or nine units inside a clean 1800 become a traceability problem. Stop the line when the lot pass rate falls under 96%.

Conclusion

Those 214 units went back as a full rework at 38 yuan each, two orders of magnitude above the cost of sampling 125 before the container left. An acceptance line earns its keep not by the bad cases it catches but by the figures nobody can argue with: 1.9 mm of wall, 32 km of travel, 3000 trolley cycles, 2 mm of play. Put them on the drawing and the station card, and travel case production becomes repeatable.

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.