How an aluminium can is made

The walls are thinner than a human hair, it holds six atmospheres, and one machine makes a couple of thousand a minute.

Punching the blank

A coil of aluminium sheet is fed through a press that punches out discs, nested to waste as little as possible.

Drawing the cup

Each disc is drawn into a shallow cup. Nothing is stretched thin yet; the metal is simply pulled into shape.

Ironing

The cup is pushed through a series of rings each slightly smaller than the last, squeezing the wall thinner and taller. This is where a squat cup becomes a can, and where the wall ends up around a tenth of a millimetre.

Trimming and washing

Ironing leaves a ragged, uneven rim, so the top is trimmed off and the can is washed of lubricant.

Coating and printing

The inside is lacquered so the drink never touches bare metal, and the outside is printed and cured.

Necking

The top is squeezed inward in many small steps so a smaller, cheaper lid will fit. The lid itself is made separately and seamed on after filling.

Where this comes from

The Aluminum Association — can recycling and manufacture; Ball Corporation — beverage can manufacturing. Every stage above is marked with how confident we are in it, and an uncertain one says so rather than reading like the rest.

• Difficulty: industrial.
• Time: milliseconds per can.
• Written for: curious adult — The whole process, plainly, with the reasons.

Questions

How is aluminium drinks can made?

A flat disc is drawn into a cup, ironed thinner than paper against a wall, and necked to take a lid — hundreds of times a minute. The stages above set it out at the curious adult level.

Can I build this myself?

This is an industrial process rather than a home build, so it is described rather than instructed.