How many sampling rounds does a Long Weapon Case need?

Answer: Two if the structure holds, three when process and padding both change, with two weeks between rounds.

Rotomolding or injection for a Long Weapon Case?

Answer: Volume and drawing maturity decide: under 600 pieces a year with a moving cavity, rotomold; above a thousand with a frozen cavity, injection.

Can an insert and dividers be combined?

Answer: Yes. Thin inserts at both ends with dividers in the middle restore 3 mm accuracy and add 0.8 kg.

How do you prove the trade-off was right?

Answer: One loaded short-haul trip, then check item position, the lid line and latch torque. All three stable means the version holds.

Three Rounds, Two Rejections: A Long Weapon Case Trade-off Log

Quick answer: The brief set 1,180 mm of internal length, under 10 kg weight, and a 1.2 m drop at minus 20 °C without a shell crack. Three prototypes later this Long Weapon Case is 3.4 kg lighter and 235 yuan cheaper per unit, having traded 6 mm of locating accuracy for daily handling.

Three Hard Numbers on the Long Weapon Case Sampling Sheet
Round One: Doubling the Wall to a Twin-Shell
Round Two: Dropping Rotomolding for Injection
Round Three: Pulling the Insert for Sliding Dividers
Four Situations Where a Long Weapon Case Is the Wrong Buy
FAQ

1. Three Hard Numbers on the Long Weapon Case Sampling Sheet

The requisition was three handwritten lines: 1,180 mm of clear length, no more than 10 kg, no crack after a 1.2 m drop at minus 20 °C.

On the drawing they collided. With 36 mm of end structure and an 8 mm pad at each end, the cavity pushed the outer length to 1,268 mm, and a twin shell already weighed 9.6 kg empty.

Round	Process	Weight	Unit cost	Outcome
One	Rotomolded 8 mm twin	9.6 kg	620 yuan	Drop passed
Two	Injection 4.5 mm	6.2 kg	385 yuan	Lighter, costly tooling
Three	Injection, dividers	6.9 kg	300 yuan	Approved

Behind those lines sat four unknowns: wall, process, padding, accuracy.

2. Round One: Doubling the Wall to a Twin-Shell

Round one took the safe road: rotomolded twin shell, 8 mm, 20 mm solid bumpers. The sample sat at minus 20 °C, dropped 1.2 m, and came back with 1.4 mm of deflection and no crack.

Long Weapon Case: grey case open on a wooden bench, egg-crate foam in the lid, empty base, two latches, shelving behind

The failure was in the hand. Latches needed 1.8 N·m to close, and the bumpers ate 44 mm, leaving 1,160 mm usable.

Rejected for buying too much strength. The note read: solid, but I need two hands.

3. Round Two: Dropping Rotomolding for Injection

Injection took weight to 6.2 kg and latch torque to 0.9 N·m. Cost moved into tooling: 38,000 yuan and 30 pieces for the rotomold, 260,000 yuan and 300 pieces for the mold.

Unit cost fell from 620 to 385 yuan, which only pays back at volume: at 120 pieces a year, tooling added 867 yuan per unit, above the rotomolded price. Most Long Weapon Case comparisons skip this: a low unit price is not a low total cost. Rotomolding suits small runs; injection suits frozen drawings. Opening a mold on a moving cavity costs 20,000 yuan a revision. Four numbers settle it:

annual volume above 600 pieces;
drawings frozen for two years;
a real need for uniform wall tolerance;
a tooling lead time beyond 45 days.

Two of the four failing points send it back to rotomolding; we met one, so round two returned.

4. Round Three: Pulling the Insert for Sliding Dividers

Round three returned to rotomolding and swapped the EVA insert for 6 mm PP dividers on a 40 mm pitch, with 15 mm foam at each end.

Long Weapon Case: grey case open in a plywood cabinet, plain lid with moulded handle, tool tray of screwdrivers, multimeter, caged lamp right

Inserts locate; dividers separate. A cut insert holds an item to 2 mm per side, while a divider only blocks sideways travel and drops accuracy to plus or minus 8 mm.

Item	EVA insert	PP dividers
Accuracy	2 mm per side	plus or minus 8 mm
Added weight	1.4 kg	0.5 kg
Change cost	new die, 1,800 yuan	move a divider
Handling	under 20 openings a month	many times a day

Frequency decided it: a dozen openings a day rounds insert pockets within three months, after which they locate worse than dividers, which have no pockets.

Accuracy was signed off at plus or minus 8 mm, not 2 mm.

5. Four Situations Where a Long Weapon Case Is the Wrong Buy

Half a comparison sits on the negative side.

Under ten moves a year with short legs: the extra locating goes unused, and a general-purpose long case costs a third less.

An item already in a rigid shell: one layer too many, and the budget belongs in stacking.

Any item beyond 1,600 mm: deflection takes over, two people lift it, and a pallet with straps is more practical.

Thirty openings a day in the field: a gasket loses rebound within two years.

One of the four reopens the comparison.

Conclusion

The approved case came out 3.4 kg lighter and 235 yuan cheaper, with 6 mm of accuracy traded for smooth daily handling. A comparison is not a hunt for the strongest specification, but for the version that matches frequency, batch size and drawing maturity. Where one of those four situations holds, a stronger Long Weapon Case is the wrong answer.

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.