Once upon a time, it would have taken a craftsman weeks to build an architect's model from drawings. Now you just press a "go" icon and, hey presto, a laser crafts a miniature edifice in resin. Matthew Richards explores the world of rapid prototyping
It's a familiar routine to anyone who works on a computer – click "print" and a copy of the document you're working on comes out of a machine. You can print pretty much anything that exists on a 2D page. Now you can print 3D models the same way, thanks to a process called rapid prototyping. Computer-driven machines use data from CAD files to create a model made of thousands of layers of resin, each a fraction of a millimetre thick. In a few hours they can produce a model that would take several days to make by hand.

Architect Ron Arad is a big fan of rapid prototyping. He says: "This technology takes two hours to do something where a craftsman would need a week. It's becoming essential." And he's put his money where his mouth is by investing in a rapid prototyping machine for his own practice, Arad Associates. He says: "I've a guy in my studio who's a very talented model maker. Well, he used to be a model maker – now he's a computer modeller."

Another pioneer of rapid prototyping is the Royal College of Art, where Arad teaches in the school of design and architecture.

In June this year, the college bought three rapid prototyping machines, which were added to its impressive range of model-making equipment. Thomas Wire, who used to look after the school's traditional range of hand-operated machines, is now in charge of Rapidform, the college's fledgeling rapid prototyping business.

"We could only afford these machines because we got a grant, and the grant stipulated that we have to cover the running costs ourselves," Wire explains. That means the machines are hired out commercially to architects and designers, and the profits used to subsidise students' rapid prototyping projects. But the college prefers to collaborate with creative, innovative types, rather than developing massmarket products for giant corporations. Wire says: "We're trying to attract people who are interested in pushing this technology forward, not people making mobile phone holders for Nokia."

One of his first customers was architect Nicholas Grimshaw & Partners, which used Rapidform's machines to model a pavilion for its redevelopment of Battersea Power Station in London. Wire says: "It was a painful experience, but we both learned a lot from it. I expect they'll come back."

Wire's experience was painful because, like all developing computer technology, rapid prototyping is prone to glitches. The machines are sensitive to light, heat and humidity. If a model is an unusual shape, it needs specially designed supports to stop it falling over while it's being made. And if a single layer of the model is made in the wrong shape, the rest of the model floats away in the tank of liquid resin, and the frustrated model-maker has to start again.

Despite the pitfalls, rapid prototyping has gone down well at Arup, which acquired a machine two years ago. "Our presentation and visualisation has changed from looking at a screen to getting a physical feeling for the structure," says structural engineer Charles Walker, who works in Arup's advanced geometry unit.

He says: "With amorphic buildings, a CAD screen gives you about 40% of the information you need. You don't have the benefit of parallax, when your eyes focus on different depths."

Arup used rapid prototyping when it collaborated with artist Anish Kapoor on his 508 ft sculpture, Marsyas, for the Tate Modern. Arup engineer Martin Self says: "The artist had a clear view of what he wanted, but the engineering was important. We'd generate the wax model and he'd tweak it. Rapid prototyping was part of the design process – it was a very useful tool."

Walker reckons young architects have become too reliant on CAD in their design process, and using CAD-generated models could act as a useful corrective. He says: "The new generation of architects designing amorphous shapes will get quite a shock. A building can look great on screen, but when you build a model of it, you realise it's not smooth, it's got bumps. A lot of architects design a blob-like building, and don't realise what it will look like in reality."

Arad claims all design schools will have to follow the Royal College and invest in rapid prototyping technology. He says: "It would be ridiculous not to – it's like not having computers." He scoffs at the suggestion that the cost is prohibitive, saying: "Computers, faxes and cars were all expensive. These are the baby days of a new technology."

Model making in the laser age

There are different types of rapid prototyping machine, but they all build models in the same way: painstakingly, layer by layer. Using the stereolithography method, a computer-guided laser shoots its beam into a tank of light-sensitive liquid resin. The areas of resin struck by the laser beam solidify, forming the base of the model. The base is then lowered a fraction of a millimetre and the laser beam shoots again, forming the next layer. The process is repeated until the model is complete. “Selective laser sintering” does the same thing with powder. As you’ll have guessed, these machines don’t come cheap. The prices for a stereolithography machine range from £100,000 to £500,000 depending on their size – the smaller ones have a 25 cm2 base, the larger ones can go up to a metre. Cheaper machines are available for £30,000, but produce only “quick and dirty” models.