3D printers

Toby Howard

The idea of a "universal fabricator" is a science fiction cliche – a machine which can create anything from raw materials, and magic objects into existence at the touch of a button. In fact, early versions of such a machine already exist. They're called 3D printers, and in a few years they're likely to hit our desktops.

It's been possible to "print" 3D objects since the mid-1980s, when Charles Hull invented the process. He was experimenting with liquid plastics called photopolymers, which harden on exposure to UV light. Hull's insight was that he could create solid objects by building them up, one thin layer at a time.

Hull filled a container with liquid polymer, and incorporated a flat shelf which intially sat just below the top level of the liquid. Then, he used a computer-controlled beam of UV light to draw out a shape on the surface of the polymer, causing the top few hundredth millimetres of plastic to harden, into a thin slice. Then, the key idea: the shelf, supporting the now solidified slice of plastic, was lowered down a tiny amount into the liquid polymer, submerging the first hardened layer, and exposing a new layer of liquid polymer to form the next slice. The first object he made this way was a tiny cup, in translucent blue plastic.

Hull called his process "stereolithography", took out a patent on it, and formed 3D Systems Inc. 1987 the company unveiled the world's first commercial 3D printer.

Today, there are several competing technologies for 3D printing, although the basic idea has remained the same – to build up 3D objects from many thin layers. In the "laser sintering" process, for example, each layer is built up by depositing a powdered cocktail of ceramic or metal, which is rolled flat and compacted. A laser then traces out a pattern on the powder, which fuses solid under the heat. Once a layer is complete, it's lowered, and a new film of powder is laid down, ready to form the next layer.

SolidScape Inc. of Merrimack, New Hampshire use another technique. They sell a machine called the ModelMaker which builds up layers using tiny blobs of molten thermoplastic, sprayed out by nozzles that fly back and forth across the printing surface, just like the heads on an ordinary ink-jet printer.

So why don't we all have 3D printers on our desks? One drawback is the cost – around $60,000 per machine. Another is that current 3D printers can only work with single materials, although it is now possible to colour different parts of the object using coloured ink granules added to the mix. A new machine from Massachusetts company Z Corporation does just this, claiming to be the world's first.

Like many emerging technologies, it won't be until a killer application emerges that the tech will get out of the labs and into the marketplace. Some industry insiders think they've already identified it – in the shape of the "Santa Claus machine". Yes, you guessed it, using 3D printers to make kids' toys, in the comfort of their own homes. One company (Toybuilders is already offering to fabricate toys to your specications – you send them a sketch and they 3D-print the finished article.

The technology is advancing rapidly, and desktop machines can't be far away. But as one wag on the Web put it: a 3D printer sounds just dandy, but can it make me a pizza?

Toby Howard teaches at the University of Manchester.