Rapid prototyping

AS RAPID PROTOTYPING matures, more designers are taking their RP production in-house. Once the preserve of major research and development departments, RP technology has become more cost-effective, with prices of smaller machines moving down towards the four-figure mark. According to RP machine distributor Laser Lines, which recently sold a Stratasys FDM 400mc to leading automotive designer Gordon Murray, customers are increasingly including smaller groups, even one-man-bands working from their kitchens, all keen to design and ‘print’ 3D prototypes.

RP’s main advantages are its speed and the scope that it gives to try out new forms, its potential for producing tooling and moulds for limited production and, when used in-house, its IP security. But there are limitations. We talked to three designers from different disciplines about how they incorporate RP into their design processes.

Structural packaging
PI Group
PI Group’s studio is bulging with technology for fast prototyping and quick tooling, all of which it uses to develop structural packaging designs. These include RP machines for one-offs and ten-offs – one for vacuum-casting and another STL 3D printer.

‘With STL you can produce shapes that aren’t producible in any other ways,’ says Steve Kelsey, a partner at PI Group. ‘There are design advantages. Because cost is relatively light compared to getting a model-maker to make it, you can refine the design to a very high level very quickly. Then you have to get into real materials to test the thing properly.”

And this, he adds, is where RP has ‘severe limitations’ for structural packaging. ‘If you want to get feedback on look and feel and limited use of closures, RP is fine. But you’re still not dealing with the real materials. A dispensing closure, for example, has to be absolutely bang-on and you can’t simulate those in RP.’

What is valuable is the use of rapid CAD/CAM technology that produces soft tooling for limited production runs using the real materials. Most of PI’s projects use a combination of techniques – a refillable pack for agrichemical group Syngenta involved STL-printed prototypes, plus vacuum-casted prototypes and other more conventional techniques. Pringles packaging, for example, combined STL-produced vacuum-casting with injection-moulding techniques.

As the technology develops to allow a finer quality of print-out, Kelsey is excited about RP’s production potential and its scope for instant variations. ‘We no longer have the need for things to be exactly the same. This is an idea that will change everything. We at PI are intensely interested in it,’ he says.

Automotive
Gordon Murray Design
It’s just six months since leading automobile designer Gordon Murray invested in a Stratasys FDM 400mc machine and already he believes it has paid for itself. ‘We use it 80 per cent [of the time] as a design tool and 20 per cent to make parts. ‘It proves out areas of a car that are particularly tricky on the screen,’ he says, of a car that are particularly tricky on the screen,’ he says,

It is presently being used to develop the design of the lightweight T25 city car, expected to be launched in 2012. It recently saved GMD weeks when the design team wanted to fine-tune a very complex and tubular part of the chassis, which otherwise would have had to have been drawn in CAD and then programmed in CNC, a lengthy process.

It comes into its own when elements of the design need to be tested ergonomically. Overnight, the designers were able to produce RP versions of the fuel input unit for the T25 for testing the next day in a ‘clinic’ with a dozen or so users to get fast feedback on how the design performed.

Similarly, a prototype for an innovative form of handbrake was also ready overnight for assessing in action on a studio test car. ‘It helps to sign off areas of car from a design point of view. You can’t move on until you’ve proved ergonomics. We’ve signed off a lot more in 3D than conventional companies,’ says Murray.

Murray likes the control that in-house RP gives the design team. And while the Stratasys has so far been particularly useful for ergonomic testing of design form, he expects to find new uses for it as the team increasingly understand what it’s capable of.

‘RP has made a huge difference in prototyping, not just in the chassis but the engines and transmission too. It’s seen [in the industry] as an enormous boon.’

Furniture/product
Barber Osgerby Associates
‘We send off the design on an STL computer file to a company in Belgium and before you know it, you get a DHL package back,’ says Ed Barber on the joys of using RP. He expects to invest in an SLA machine in the foreseeable future so his own consultancy can swiftly prototype designs.

But RP remains very much just one stage, along with old-school model-making, in Barber Osgerby Associates’ design process. Every design starts out in the sketchbook and then moves into a basic 3D cardboard or foam model. ‘It’s stuff we can do very quickly in-house that’s just proportionally correct. It’s always wrong, in some way, but that’s the point,’ says Barber.

After further refinement, perhaps with the aid of modelling clay and an external model-maker, BOA sends off its design via computer file for RP. In the case of its new signed edition of the Tab lamp for Flos, out this month, RP was just used for the crucial shade component.

The resulting resin prototype greatly assists in refining the design, but is no substitute for a prototype in the appropriate materials, says Barber. Flos did this in die-cast aluminium using a reflector out of porcelain, chosen for the softness of the light. This prototype is used to test light refraction, heat and stability over days of constant use, something an RP prototype couldn’t manage.

BOA has used external RP facilities since 1999, but for it, RP will never replace more traditional prototyping methods. ‘I don’t think RP will take over. We only use it for speed,’ says Jay Osgerby. ‘There is a danger that you [could] miss out on an opportunity in the design process for model-making in the studio, where the object is in your hand physically… When you are making cardboard models invariably you make mistakes, and sometimes that enhances the project.’