How copper wire is made

Copper rod is pulled through die after die, getting longer and thinner each time, never losing volume.

stations: 6
things upstream: 7
raw sources: 4
steps from the ground: 3

The short version

Copper wire is drawn from cast copper rod. The rod is pulled through a succession of dies, each one narrower than the last, which lengthens it. The metal is annealed between pulls to soften it, because drawing hardens it, and the finished wire is wound on spools. Telephone wire is drawn 20 to 30 times from rod stock.

Cast copper rod

Refined copper cathodes are melted and cast continuously into a thick rod, which is then reduced by rolling into a coil that wire drawers buy as their raw material.

Goes in
Copper
Clean the rod

The rod is cleaned so the surface is bright and smooth. Dirt or oxide here would scratch the dies and the wire.
Pull it through a row of dies

A drum pulls the wire through a hole in a die, and the wire gets thinner and longer. The dies are made of tungsten carbide or diamond. A continuous machine has a series of dies, with 3 to 12 per machine, and each drum turns faster than the one before.
Anneal to restore softness

Cold working leaves the metal hard. Heating it between draws counters that, and a last anneal on the finished wire maximizes both its ductility and its electrical conductivity.
Draw it fine

Fine wire goes through smaller and smaller dies, with a lubricant bath to keep friction down. Very fine wires are often drawn several together in a bundle.
Spool or strand it

Finished wire is wound onto spools. Several thin wires can be twisted together into stranded cable, which bends more easily than one thick wire.

End of the lineCopper wire Next it goes into computer mouse, headphones, solar panel and 31 more.

Worth repeating

Electrical wire takes about 60 percent of all the copper used.
Copper is the preferred electrical conductor in almost every kind of wiring, except overhead power transmission lines, where aluminum is often preferred.
In some wire, a thin copper film is left on after drawing to prevent rust or help with soldering.