Designs you can grasp: Solid models can be made rapidly from drawings

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BRITISH companies are cutting up to 70 per cent off product development costs by adopting the technology of rapid prototyping, which allows designers to turn 3D computer drawings swiftly into solid models.

The leader in the field is the car manufacturer, Rover Group. Using rapid prototyping, the company is typically cutting development time by 60-90 per cent and costs by 40- 70 per cent, according to Graham Tromans, principal engineer for the technology.

For example, designing a heater case by the traditional route costs pounds 200,000: using rapid prototyping this was cut to pounds 50,000 - and completed in one third of the time. Designing a gear shift used to cost pounds 12,000: with rapid prototyping this was cut to pounds 4,250.

Rover is a sponsor of the Rapid Prototyping and Tooling Consortium at Warwick University, set up in March this year to encourage UK manufacturers to use the technology. It now has 70 members in the automotive, medical, consumer goods, electronics and engineering industries.

Lee Styger, its manager, says: ''Complex designs often require many iterations, a major factor affecting product lead times. This is overcome by rapid prototyping, which converts computer-aided design data into real models, typically in a matter of hours.'

Almost all rapid prototyping systems work on a layering technique. Special software cuts a computer-aided design of the component into slices, feeding the data for each layer to the rapid prototyping machine.

The most common rapid prototyping machines use a technique called stereolithography. The data describing each slice controls a laser which 'draws' the slice on a layer of photosensitive resin that is instantaneously solidified by the laser. This slice is then lowered into the bath of resin and the next layer is constructed on top, and so on until the model is complete. Other systems depend on the same layering technique but use a powder that is fused into a solid by the laser, have a head that extrudes plastic or wax to form each layer, or cut each section out of paper and stick them together. Models are typically accurate to plus or minus one micron (the thickness of a human hair).

Originally, rapid prototyping was used to make models to assist in the visualisation of a new product. In the past year, the technology has developed to the extent that master patterns for casting and metal moulds can be made in days rather than months, and in some cases rapid prototyping machines are producing actual components.

The next development of rapid prototyping, expected next year, will use the same principle as ink-jet printers to create layers of the model. Philip Dickens, at the Centre for Rapid Prototyping in Manufacturing at the University of Nottingham, says this will allow the construction of rapid prototyping machines that are no bigger than a laser printer and can be used on the desktop rather than in the workshop. 'When designers press the button to get a hard copy, they won't get a drawing, but a solid wax model,' he says.

'The main use of these machines will be for visualisation. Most models will have a life of just a few minutes before they are thrown in the bin because the designer realises there is a mistake.'

One of the barriers to widespread use of the rapid prototyping machines has been cost. Stereolithography machines made by 3D Systems of the US, which claims to have invented the technology, cost pounds 100,000- pounds 600,000. Running costs are 10- 15 per cent of the capital costs per annum. Even so, cost savings are so great that the machines rapidly pay for themselves.

In November, the Department of Trade and Industry sponsored one of its Overseas Science and Technology Expert Missions to look at developments in rapid prototyping in the US. The team visited some of the key industrial users of rapid prototyping, including General Motors, Ford, Chrysler, Texas Instruments, and Johnson & Johnson. One company reported saving dollars 600,000 (pounds 405,000) in the development of a single part, while another said it had saved dollars 300,000 in the first year.

Chrysler has saved dollars 3.5m in the three-and-a-half years since it introduced rapid prototyping, and says it will cut the design cycle from concept to first production car from 56 to 28 months.

The technique is not just applied to heavy industry. Mr Styger reports that a chocolate company uses it to design moulds for chocolate Santas and Easter eggs.

(Photograph omitted)

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