Quick answer: Three lots, 36 cases, every rejection traced to three numbers: seam, wall, cavity. Six checks a buyer can run on site, each with its tool and pass line.

Table of contents

  • Why the three lots failed
  • Six checks you can run on site
  • Derive the cavity, do not copy it
  • Score the six, then cut the list
  • FAQ

1. Why the three lots failed

Between September and November 2025 a storage unit took 36 missile box units in 3 lots of 12. Four came back from the first, 7 from the second, all 12 from the third: light through the lid seam, thin walls, a short cavity.

The first four failed at the seam. Lid closed and latched, a 0.4 mm feeler slid in mid-span while a 0.1 mm blade would not enter under the latch: the missile box lid lacks stiffness, so force sits on 2 latch points.

The next 7 failed on wall. The drawing called for 8 mm; a gauge read 6.2 mm at the four inside corners and 7.6 mm at the base centre, a 1.4 mm spread on one case. The missile box corners are thinnest and crack first.

Lot three: cavity drawn at 1180 mm, measured 1163 mm, cradle 1170 mm, so it went in at an angle and came out frayed. Of 5 suppliers, 2 made these lots, and every sheet said appearance good.

2. Six checks you can run on site

A missile box criterion must yield a number within 3 minutes and repeat to within 5% in other hands. Six survive.

CheckToolPass lineHow it fails
Lid seam0.2 mm feelerat most 2 entriesgap between latches
Wallultrasonic gaugethinnest above 7.2 mmcorners thin
Latch preloadpush-pull gauge150 N minimumone hand opens it
Empty weightplatform scalewithin 1.5 kg4 kg spread per lot
Cavity diagonalstape2 mm maximumliner will not seat
Gasket squeezedepth gauge25% to 30%squashed past 40%
Missile Box: three black hard cases on a dark steel cabinet, two closed, one open with egg-crate foam and cut liner
Missile Box: three black hard cases on a dark steel cabinet, two closed, one open with egg-crate foam and cut liner

These missile box pass lines are back-calculated for a 96 kg load stacked 4 high.

Weighing is the step buyers skip. A case specified at 41 kg that reads 39 kg has less compound; one reading 44 kg has wall where it does no work. A 4 kg spread across 3 cases means an uneven wall.

3. Derive the cavity, do not copy it

A missile box cavity cannot come from a catalogue. Cradle outline plus cushion plus clearance gives the cavity; wall and ribs come last.

Cradle 1170 by 360 by 340 mm, cushion 25 mm per side, clearance 3 mm per side: the cavity must reach 1226 by 416 by 396 mm, so a nominal 1180 mm leaves you 46 mm short.

Nominal cavityMeasured cavityCushion per sideCradle that fitsVerdict
1180116325111357 mm short, unusable
12601244251194fits, no margin
1340132230126292 mm spare, usable

Two dimensions stay hidden: corners carry a 15 to 20 mm radius, so a square cradle needs 20 mm more per side, and 2.5% to 3% shrinkage puts a 1340 mm cavity on a 1375 mm mould.

4. Score the six, then cut the list

Weight a missile box by consequence: wall 25, seam 20, cavity 20, latch 15, empty weight 10, gasket 10. Under 70, a quote never reaches the price round; under 40% of its own points, a line drops out. One supplier scored 78 with a 6.2 mm wall and was still cut.

Missile Box: long black hard case open on a pale grey background, three latches and one handle in the lid, a full-length foam channel
Missile Box: long black hard case open on a pale grey background, three latches and one handle in the lid, a full-length foam channel

Two quotes sat 23% apart with 6 points between them, so the gap was not process: split compound weight, latch count and test list into 3 columns and the 23% lands on wall and salt spray, 180 yuan a case.

Conclusion

Three returned lots produced one sheet: feeler along the seam, gauge at 4 corners, 150 N on the latch, 41 kg on the scale, tape across the diagonals, depth gauge on the gasket. Six numbers, a 70 point floor, a 40% veto: enough to put a price on the missile box.

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.

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