This is quoted from http://www.dailymail.co.uk/sciencetech/article-2117570/Amazing-3D-printer-action-Watch-working-wrench-printed-powder.html .

Amazing 3D printer in action: Watch a working wrench being made from powder

By Ted Thornhill
PUBLISHED: 20 March 2012

We’re going to need a lot of tools as we expand into space – to build and maintain space stations and craft.
However, the problem of how to replace tools should they break has always been a worry. After all, it’s quite an undertaking to fly them into orbit.
But now scientists believe astronauts will be able to build unlimited replacements – simply by printing them.

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Hi-tech: The Z Corporation's 3D printer can make just about anything

Image is everything: The wrench is scanned into a computer

It sounds like science fiction, but a YouTube video made by National Geographic shows that the remarkable process is actually science fact.

Theoretical physicist David Kaplan, from Johns Hopkins University, visits a company called Z Corporation in Burlington, Massachusetts, which specialises in 3D printers that can make almost anything – even with moving parts.
In the amazing film a huge adjustable wrench is first of all scanned into a computer, down to the accuracy of 40 microns – slightly less than the width of a human hair.

Remarkable: The finished wrench is pulled out of the powder tray

Robust: It's even strong enough to undo a nut

The image is then sent to a printer that doesn’t use ink, but a ‘specially engineered composite material’ that starts out as a powder and is then bound together with a type of resin.
This is what the printed wrench is made from.
Within 90 minutes Dr Kaplan is shown a fully working, robust copy of the original wrench that even features the adjustable head.
He said: ‘So going into space, you just take a printer and you can print whatever you want.’