Should cartridge box capacity be counted by volume or by cells?

Answer: By cells. Nominal volume describes the outside; only net volume after dividers tells you what fits.

EVA or PE for the insert?

Answer: EVA where location matters and the case opens often, at 30 kg/m³; PE where budget is tight, at roughly 20% less.

How thick must a lid be for a five-high stack?

Answer: Rib alignment matters more than thickness. Lid ribs must sit over the base channels below, and a 72-hour test should hold deflection under 3 mm.

Is IP67 always necessary?

Answer: Only for open yards, vessels and wet climates; a dry warehouse is served by IP54.

Can orders below 300 units be customised?

Answer: Yes, usually on an existing cavity with a new insert and colour. Tooling is charged in full, so spend on foam.

How to Choose a Cartridge Box: Five Criteria

Quick answer: Work through five criteria in order: capacity and compartments, insert, stacking and forklift handling, sealing class, then batch size and budget. Each one fixes the numbers the next needs, and two quotations become comparable only then.

Five Criteria for Choosing a Cartridge Box
Capacity and Compartments: Count Cells Before Volume
Inserts: Locating, Cushioning and Access
Stacking and Forklift Handling: Load Paths Through Base and Lid
Sealing Class, Batch Size and Budget
FAQ

1. Five Criteria for Choosing a Cartridge Box

Most buyers describe a cartridge box in two sentences: it must hold the load and survive the trip. At quotation stage those sentences become five checkable numbers, each answering a different question: daily use, movement inside, the journey, dryness, and price. Order matters too, since capacity comes before the die and the stack pattern before lid ribs.

Criterion	Number to confirm	Typical range	Cost of a mismatch
Capacity and compartments	Internal size, cell count	400×300×150 mm, 12 cells	Cells too deep, gloves catch
Insert	Foam density, compression	30 kg/m³, 25% compression	Loose fit, chipped corners
Stacking and handling	Layers, fork pocket height	5 layers, 100 mm pocket	Base collapse, forks through floor
Sealing	IP class, gasket compression	IP67, 25% to 30%	Damp interior, valve failure
Batch and budget	MOQ, tooling split	300 units, tooling separate	Low price, tooling unpaid

2. Capacity and Compartments: Count Cells Before Volume

Capacity in a cartridge box is counted in cells, not litres. A 400×300×150 mm interior is sold as 18 litres, but walls and dividers leave about 13 litres usable. Twelve cells of 60×90 mm fill one layer; depth above them is dead space.

Cartridge Box: olive green case tilted against a dark background, lid facing up, one latch, round pressure valve and folded handle visible, reinforced corner guards

Cell depth drives the handling motion. A cell 20 mm deeper than the carton forces gloves to the bottom; a shallower one lets the lid press on the carton. Five to eight millimetres of clearance over a thin pad is the workable band.

3. Inserts: Locating, Cushioning and Access

An insert does three jobs at once: locating, cushioning and access, all drawing on the same thickness. Locating wants density and low rebound, cushioning wants closed cells, access wants finger relief cut into the pocket rather than a wider pocket.

EVA at 30 kg/m³ rebounds to about 95% after 25% compression and cuts cleanly; PE at 25 kg/m³ costs roughly 20% less. Both laminate a dense skin onto a soft base at around 110 °C, with die-cut pockets 0.5 mm over the item.

4. Stacking and Forklift Handling: Load Paths Through Base and Lid

Stacking is not a claim about column height but about whether base and lid can pass load into the ground. A case of 18 kg with 12 kg inside puts about 120 kg on the bottom of a five-high stack.

Cartridge Box: three olive green cases on a wooden table, the medium one open with egg-crate foam and cut cells, a small one in front

Load travels through base ribs, lid ribs and corners. Ribs that land in the lid channels below send force through structure rather than a plastic wall; misalignment leaves white marks in the lid centre. A 72-hour static test should keep deflection under 3 mm.

Fork pockets 100 mm high and 200 mm deep let forks enter without touching the floor; without them a pallet adds 120 mm and costs two layers per load.

5. Sealing Class, Batch Size and Budget

Sealing follows the environment. A dry warehouse needs IP54; an open yard or ship's hold needs IP67, thirty minutes at one metre. The gasket is silicone at 50 Shore A, compressed 25% to 30%; less leaks, more takes a set. A valve opening between 0.02 and 0.05 bar keeps the lid usable.

Batch and budget decide whether the first four survive. Tooling is quoted separately from 300 units; above 1,000 the unit price falls 12% to 18%, and again at 3,000. At low volume it is cheaper to change the insert than the case.

Batch	Tooling treatment	Price index	Typical use
300 units	Fully charged	100	Trial fit, small issue
1,000 units	Spread over three years	86	Annual replenishment
3,000 units	Spread over ten years	74	Multi-unit standard issue

Conclusion

The difficulty is not the number of criteria but their order. Capacity gives the insert its dimensions, stacking gives the ribs their depth, sealing and batch size close the quotation. Chosen that way, a cartridge box rarely comes back for rework.

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.