Shaping the future

Rapid methods in prototype production.

A company wanting to engage in 'rapid manufacturing' now has a wide choice of machines, processes and technologies for getting its product ideas quickly into production. What many of these processes are essentially about is 'growing' parts out of minuscule pieces, as opposed to traditional manufacturing methods of machining, shaping or injection-moulding materials.

Commonly, rapid manufacturing (also known as rapid prototyping) involves using laser technology to solidify or shape liquids or materials very precisely. Imagine being able to produce an object with a lattice-work interior simply by programming a machine to create this shape out of liquid plastic - removing the need to create and use a cast.

Gordon Murray, who runs his eponymous automotive design company, is using a protopying machine to help bring to market the company's first automotive design project, a city car code-named T25. The machine will be used to build components for automotive design and tooling, such as interior instrument parts, trim panels and fittings, exterior components, wind tunnel model parts and parts for running test vehicles.

Murray initially started using rapid prototyping at McLaren Cars for Formula One racing cars. "We learnt a lot about rapid prototyping techniques, equipment and materials, but more importantly that it would be much more than just equipment for making prototype parts - it would be a design tool."

He claims the current T25 programme will lead to volume production of about 100,000 units a year. The first two years will achieve five running prototypes, he says, and he hopes during that period to sell the programme on to an original equipment manufacturer (OEM).

"The idea is that we get kept on as engineering consultants, and work with them [the OEM] through to job one, which would mean somewhere between 50 and 100 prototypes going through a development programme - things like hot and cold weather testing," Murray says.

"That is when a rapid-prototyping machine really comes into its own because, even with up to 50 prototypes, we would still probably be making the first batches using rapid prototype components for interior panels and instrumentation, but at the moment we are using it much more as a design tool.

"Overnight we can make a model of our chassis structure, for example, for the designers to review the next day in three dimensions, or make a specific area of the car where we have a clash between styling and engineering. We can use it for practical things like fuel nozzle entry so that we can put that on a full-size mock-up and check the ergonomics and comfort factor when filling the car up."

Murray expects to produce prototype parts before next year. An OEM will, he hopes, then use similar machines prior to tooling up for volume production.

"If an OEM is making 100 prototypes, the first third will use a lot of rapid prototype components, the second will use more off-tool pre-production parts, and by the time you do the final third, you should really be all off-tool because you are proving out the production process by then," Murray says.

"This is a complete rethink, not just on car design, but also the manufacturing process. This is another area as a design tool where this machine has been fantastic because we are actually using scale model rapid prototype parts to check out the assembly process in scale.

"Most people do that straight off CAD [computer-aided design], but it is never the same in three dimensions by the time you actually have the parts and you are trying to decide, for example, whether the front suspension should go on ahead of the inner wheel arch lining, or whether the steering mechanism should go in before the suspension. We can actually do that using rapid prototyping."

Layered approach

Not surprisingly, Graham Tromans, manager of the rapid manufacturing consortium at Loughborough University, UK, is a big advocate of rapid-manufacturing techniques over traditional machining.

"Because you have no tooling constraints and you do not have to worry about draft angles, re-entrants or voids, you can now manufacture what would have previously needed a five- or six-piece assembly in one piece," he says.

Tromans has been involved in rapid prototyping and rapid manufacturing since 1990 when, he says, he introduced Britain's first SLA-500 machine, which applies the 'stereolithography' method of using a laser on liquefied materials to create layers to build solid shapes - also known as 'layering'.

Until the end of 2002, he managed the rapid-prototyping and tooling facility at Rover Group/Land Rover, which also involved work in conjunction with the BMW facility in Munich. After BMW sold off Rover Group, he worked with Ford Europe, Jaguar, Aston Martin and Volvo.

"Prior to this bit of kit coming in, all the prototypes would have been handmade from 2D drawings or modelled in clay," he recalls. "As principal engineer on concept cars, I would be given a clay model from which we would design the moulds to manufacture fibreglass parts.

"When we introduced the first SLA-500 at [Rover in] Canley, Coventry, it was difficult to get people to use it because it needed high quality CAD data, which meant they needed to spend another couple of days on it to get it right. When I asked some people to support me by giving me the right data, after which time they were getting parts in a couple of days while other people were waiting a month to get theirs, people at the top started asking questions like: 'if they can do it, why can't you?'."

In 1992, Rover moved its Canley rapid-prototyping facility to Warwick University. Professor David Wimpenny, head of rapid prototyping and manufacturing at De Montfort University, first got involved in the technology at Warwick.

Wimpenny says: "When you build a car [with rapid prototyping] you can make a full-size mock-up to make sure everything fits together to avoid a very expensive cock-up before you start casting and injection-moulding.

"In more recent years, 'layer' manufacturing has gone from making prototypes [to making] production parts. For example if you want a plastic component, even if it is only for 100 parts, you have to make an injection-moulding tool or machine it from a solid material, where you have to limit the geometric complexity in order not to make the part too difficult to machine.

"With rapid prototyping, there is no tooling or geometric limitation. There is no cost penalty for small-volume manufacturing. If you can visualise it, we can make it, but it is still quite difficult for designers to understand that they can be quite adventurous and not take risks like they would with an injection-moulding tool.

"If you are machining a 20kg block of metal to make a precision part for an aircraft, for example, you could waste 19kg of the material. Metal-based rapid manufacturing is still evolving but new applications are driving the industry.

"In November we have a craft event at the jewellery quarter in Birmingham, which will look at digital design and manufacturing of customised jewellery. European jewellers are under pressure from cheap Chinese mass-produced goods, so if they can offer a quick turnaround bespoke service, they can still compete."

Wimpenny argues that the difference between a home printer and a rapid prototyping machine is not that significant. And whereas early rapid-prototyping machines sold for upwards of $100,000, he foresees machines costing under $1,000 in the not-too-distant future.

Design freedom

According to Richard Hague, professor of innovative manufacturing and head of the rapid manufacturing research group at Loughborough University, rapid manufacturing engineers have an "extreme" design freedom which they do not normally get in conventional manufacturing.

He says: "The existing CAD systems are not particularly good for rapid manufacturing because they cannot design the kind of complexities that we can make, so one of the research issues is in design tools to maximise the benefits of rapid manufacturing."

Loughborough University is a key player in the ambitious Custom-Fit, a Europe-wide industry-led project to investigate the rapid production of customised health and safety products such as helmets and prosthetics.

Hague says: "Most rapid manufacturing to date has been in polymers. The main process that has been used for rapid manufacturing in plastics is SLS [selective laser sintering]. Rapid manufacturing will not overtake injection-moulding for all components, but one exciting area in the future is making lightweight metallic products."

Dr Gregory Gibbons, head of rapid prototyping and manufacturing at Warwick University, has worked with companies like Rolls-Royce to introduce rapid tooling for primary aerostructures like titanium aircraft nose cones.

 "We introduced a laser-based sand machine using particles of about 50 microns, so the surface is not as smooth as what comes out of a traditional sand-casting process, but it allows you to make very complex structures," Gibbons explains.

The sand particles are polymer-coated and laser-sintered to bond them together to quickly produce a casting for an engine cylinder head, for example. The oil and gas industry uses the technique for making complex valve structures, the aerospace industry uses it to make gearboxes, and the automotive industry uses it to make brake callipers, cylinder heads, water jackets, and so on.

"We are getting more involved in medical implants as well," Gibbons adds. "We can build using medical-grade titanium. You can also make a ceramic bone implant with the structure needed to get fluids in and the waste materials out.

"You actually deposit the cells inside it and the bone proteins which will encourage the bone to grow."

According to Wimpenny, machines currently producing high-value items such as jewellery and medical implants will eventually find their way into people's homes.

And rather than going to a toy shop, customers will be able to download a file from a manufacturer and print their toys. In the future, making and shipping toys is not what the toy companies will want to do - they will want to design the toys and sell the intellectual property to customers.

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