What should a rotomolded case comparison check first?

Answer: Annual volume. It decides whether the mold can be amortized, and the other three items rest on it.

Is a rotomolded tool worth it at 200 units a year?

Answer: Usually not. A CNY 80,000 mold over 200 units adds about CNY 400 per case before labour.

For sea freight, does a rotomolded case beat a metal one?

Answer: Salt spray attacks folded metal edges, and rust appears after 240 hours. With no metal substrate, a scratch starts no corrosion.

Is a thicker wall always better?

Answer: No. Going from 4.5 mm to 6 mm adds about 1.6 kg, may not add a stacking tier, and raises freight first.

Which cost is most often missed in a quotation?

Answer: Rework and spares. Whether latches, hinges and gaskets come apart sets the year-five spend.

Rotomolded Case Comparison: How It Differs from the Alternatives

Quick answer: A rotomolded case competes with blow molded, bent metal and thermoformed panel cases. The gap is not one strength figure but four items: tooling, break-even volume, wall and rib freedom, repairability.

Four Comparable Items to Align First
Wall and Rib Freedom Against Blow Molded Cases
Weight and Repair Cost Against Bent Metal Cases
Stiffness and Volume Threshold Against Thermoformed Panels
Reading the Four Options in One Table
FAQ

1. Four Comparable Items to Align First

Options compare only when four parameters line up: outer size and internal volume, wall thickness with rib layout, annual volume, and repairability. Let one drift thirty percent and every cost figure afterwards is meaningless.

Tooling outlay decides whether a small batch starts; break-even volume decides where two cost curves cross. Wall freedom decides rib count, repairability the year-five bill.

Item	What to pin down	Cost of skipping it
Size and volume	Outer size, internal clear size, wheels	Unit prices on different volumes
Wall and ribs	Nominal wall, rib count, rib depth	Thin-wall price against a thick-wall part
Annual volume	First-year take, three-year forecast	Break-even miscalculated, decision reversed
Repair path	Field welding, spare part commonality	Rework and replacement left out

2. Wall and Rib Freedom Against Blow Molded Cases

Blow molding pushes a parison against the mold wall with air, so thickness follows the parison and thins at corners. At the same outer size, blow molded walls run 2 to 3 mm; a rotomolded case holds 4 to 6 mm with both faces within 0.8 mm. A 4.5 mm wall with four recessed ribs stacks five tiers at 320 kg on top; a blow molded case of that footprint needs a pallet at tier three.

Rotational molds are open steel or aluminum tools, so ribs and latch seats are cut into the cavity and four to six ribs form in one shot. Blow molding manages one or two shallow ribs before the wall stretches thin. Past a 900 mm long edge, rib placement buys more than another 0.5 mm of wall.

3. Weight and Repair Cost Against Bent Metal Cases

Bent sheet metal skips heavy tooling; fixtures at about CNY 12,000 start a small batch. The price is weight and corrosion. At 80 liters, a rotomolded case weighs 9.2 kg empty, cold rolled steel 15.6 kg, aluminum 6.8 kg. In humid sea freight, steel rusts at folded edges and welds after 240 hours of salt spray, and the fix means sanding and repainting.

Polyethylene shells take hot air welding at 210 to 230 °C, keeping roughly 85 percent of the original falling-dart strength. Repainting metal rarely hides the scar, leaving about 2 color-difference units against the sample.

4. Stiffness and Volume Threshold Against Thermoformed Panels

A thermoformed case is an ABS sheet drawn over a tool and riveted to an aluminum frame. The tool costs about CNY 35,000 and arrives in ten days. The shell is 2.5 mm thick, so stiffness sits in the frame; a sharp corner leaves a dent that will not spring back.

Below 250 units a year, a panel case lands about 18 percent under a rotomolded case, because tooling amortization and per-unit labour vanish. Above 600 units, the rotomolded case pulls ahead on unit cost and stops paying frame riveting labour. Between the two, check the long edge.

5. Reading the Four Options in One Table

Read in order: volume, outer size, repair method, then unit price. Price comes last; once the first two are wrong the figure means nothing.

Item	Rotomolded case	Blow molded case	Bent metal case	Thermoformed case
Main tooling	Steel mold, CNY 80,000	CNY 140,000	Fixtures, CNY 12,000	Aluminium tool, CNY 35,000
Typical wall	4 to 6 mm	2 to 3 mm	1.0 to 1.5 mm steel	2.5 mm sheet
Empty weight, 80 liters	9.2 kg	7.5 kg	15.6 kg steel, 6.8 kg aluminum	5.4 kg
Tooling lead time	22 to 28 days	25 to 35 days	7 to 10 days	10 to 15 days

Under 250 units, thermoformed and metal routes move faster. Between 250 and 600, size and duty cycle decide. Above 600 units with a long edge past one meter, a rotomolded case has amortized its mold and wall freedom turns into an advantage. Read repair second: capability sets the year-five bill, a quotation shows only year one.

Conclusion

No route wins everywhere; each has a volume band where it makes sense. The real strengths of a rotomolded case are wall and rib freedom, a corrosion path with no metal substrate, and a shell that is welded rather than scrapped. Its weakness is tooling outlay and per-unit labour. Put volume, size and repair method into the enquiry, and the rotomolded case comparison will hold up.

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.