Prototyping – the means to an end

Posted on 10 Aug 2009 by The Manufacturer

The process of prototype development has changed dramatically from the days requiring cumbersome scale wooden or clay models. But with a variety of different technologies now available, including full digital as well as rapid 3D prototyping, which one is best and is the physical prototype a thing of the past? Malcolm Wheatley investigates.

In March 2006, power tool manufacturer Black & Decker took delivery of a 3D printer from Stratasys, a specialist supplier of rapid prototyping machines. But the printer in question, stresses Black & Decker technology manager Steve Swaddle, had been supplied strictly on a loan basis.

“There was a sense that you tend to get what you’ve paid for — and at £17,000 or so, the printer was significantly cheaper than stereolithography or laser sintering machines costing £200,000 or more,” he says. “We had severe doubts that a machine costing so little would do what we wanted.” But the printer, borrowed for a two-week evaluation period, never went back. Within days, the company had made the decision to purchase it.

“Within 24 hours it was running directly from our CAD development system, and generating real parts and it’s been in almost daily use since then,” says Swaddle.

And it paid for itself within three months, according to Swaddle, thanks to a sharply reduced requirement for inhouse CNC milling and outsourced stereolithography.

Yet such stories are surprisingly rare. Even as they battle against shrinking product lifecycles and pareddown development budgets, many manufacturers struggle to get past first base with technologies such as rapid and digital prototyping. So what barriers stand in the way of adoption and how can manufacturers surmount them?

Digital vs rapid

One common confusion occurs right at the start.

While manufacturers hear of rapid prototyping, they also hear of digital prototyping. “Which is better?” they understandably ask. The answer: neither — the two approaches, if anything, are complementary rather than competing.

In large part, the choice comes down to what is trying to be achieved. At Cambridge-based technology and product development consultancy Sagentia, for instance, both digital and rapid prototyping are used.

“Digital prototyping is good for seeing how parts fit together, and ensuring that clearances and tolerances are accurate,” says Ian Anderson, head of product development. And to achieve that, he points out, there’s often no need to go beyond the CAD screen.

While a physical prototype could be built, digital prototyping through the use of 3D CAD software is significantly cheaper, as well as quicker.

Aero engine manufacturer Rolls-Royce, for example, at one time built wooden mock-ups of each new engine, physically making up and mounting the pipework that went from one part of the engine to the other. No longer. These days, it’s all done digitally.

“Designing digitally offers not just the ability to optimise the design of a part, but also optimise the process that will be used to manufacture and then assemble it,” says Geoff Haines, managing director of Oxfordshirebased Desktop Engineering, a distributor and business partner of CAD and 3D simulation specialist Dassault Systèmes. “With a process or product that might run for years, digital optimisation is cheap, and fast, and almost always worthwhile.”

Something to grasp

Even so, most manufacturers find that there comes a time when a physical prototype is required. “I’m a great believer in handling and testing things, rather than going straight to tooling,” says Sagentia’s Anderson. “CAD doesn’t tell you how something feels in the hand.” And just as importantly, perhaps, a physical object may be required for training purposes, for photography for catalogues or even market testing. Consequently, even the most ardent proponents of digital prototyping concede that going to market without first constructing a physical prototype is in most cases a step too far.

“There’s still a need for physical prototyping — but digital prototyping means that you need fewer physical prototypes, and that you need them later in the development process,” notes Richard Blatcher, northern Europe head of manufacturing marketing for CAD vendor Autodesk.

Tewkesbury-based specialist automotive manufacturer Smart Stabilizer Systems, for example, is one such Autodesk customer that has used the company’s Inventor 3D CAD system to digitally model products, delaying the need for physical prototypes until much closer to product launch.

And the company’s experience with digital prototyping, adds Blatcher, highlights yet another advantage of the technology—one that manufacturers aren’t necessarily looking for when they first adopt it. “Staying digital allows you to refine and develop the design more intensively: error rates can reduce quite sharply,” he says.

But given that physical prototypes will eventually be required, what options are available for producing them? And, what’s more, producing them rapidly? Some approaches come close to being accelerated versions of production processes. Chippenhambased Fascia Graphics, for example, produces flexible keypads for manufacturers who incorporate such data entry devices into their products. For Fascia, rapid prototyping involves cleverly leveraging a plastic printing solution borrowed from the sign-printing industry.

“Prior to discovering Fascia, there was no alternative to going down the production route and paying £1,000 or so for a full prototype keypad — and even then, we might make changes, and consequently need another prototype manufactured,” says Geoffrey Swales, managing director of Bradford-based electronics manufacturer BioDigital. Now, he reports, he can get a realistic-looking prototype in three days, rather than three weeks and at a fraction of the cost.

And Birmingham-based specialist CADCAM vendor Delcam points up yet another option: the cost-efficient production of small batches of parts, where the prototype in question might be a short product run for market testing, or a one-off special requirement.

“Where a prototype is in effect a real, fully-functioning part, the challenge can be producing it without disrupting ongoing manufacturing operations,” notes Delcam marketing manager Peter Dickin.

American customer Owens Industries, of Oak Creek, Wisconsin, for instance, uses Delcam’s PowerMILL CAM software to produce very small batches of complex components to very tight tolerances.

PowerMILL offers not just much faster component programming time but more efficient toolpaths, so the parts are produced more quickly. A recent project saw the company produce 25 parts for an aircraft braking system. “With our previous software, the new parts would have taken two months to produce,” says Owens vice-president Mark Plesnik. “With PowerMILL, because of the faster programming and the quicker machining, they took two weeks.”

Yet the need for the classic ‘one off’ prototype remains.

To deliver this, rapid prototyping solutions tend to revolve around three separate underlying technologies: stereolithography (SLA), selective laser sintering (SLS), and fused deposition modelling (FDM), the latter being the Stratasys technology that was adopted by Black & Decker.

Each technology produces prototypes with different characteristics and material properties. Sintering, for example, fuses plastic particles together, while 3D FDM printing builds up parts by laying successive layers of thermoplastic. The resulting prototypes aren’t true prototypes of the final part (they’re made from plastic rather than steel for instance) but physical copies that for most purposes are good enough.

Costly misconceptions

In each case, though, it often turns out that the barrier to wider adoption isn’t so much to do with the technology, but flawed perceptions as to the cost of the parts, as well as their ruggedness.

“There’s a widespread misconception that SLA and SLS are expensive, when quite simply they’re not,” says Sagentia’s Anderson. As with many new technologies, it seems, high costs when a technology is introduced create a lasting impression that is difficult to eradicate, even when prices are far lower.

“Since around 2002, there’s been a real transformation in the value proposition of 3D FDM printing,” observes Tim Heller, Stratasys’ European managing director.

“Printer costs fell from around £200,000 to around £20,000—and, what’s more, produced parts that were built up from a much more robust material.” And similar misconceptions as to cost, it turns out, cloud perceptions of digital prototyping, too. “In the marketplace, the perception is that the technology costs between £15,000 and £20,000 per seat in licensing costs, and that just isn’t so,” says Autodesk’s Blatcher. “The starting point is much lower, around £1,000 a seat in many cases.” And potentially even lower still, given the emergence of new ‘software as a service’ based deployment models.

Hampshire-based Dezineforce, for instance, offers hosted CAD and simulation packages from a number of leading vendors on its high-performance computing clusters, which manufacturers can access remotely on a subscription basis, using them as needed.

“The ability to compress design cycles is increasingly linked to a company’s competitive edge,” observes Dezineforce chief executive Peter Collins. “A design process that might take three months conventionally can be reduced to between two and four weeks.” Yet the final barrier to adoption may lie in the supply chain, rather than in the manufacturing enterprise itself.

Hampshire-based RF radio equipment manufacturer Wood & Douglas, for instance, has been increasing its use of both digital and physical rapid prototyping over the past three years, reports managing director Alan Wood.

But providing in-house produced SolidEdge CAD files to local third-party SLS specialists to obtain realisticlooking epoxy plastic cases was one thing, getting those cases machined from metal quite another.

“Everyone we went to said: ‘Give us the drawing’ and we didn’t have one, just a CAD file,” recalls Wood.

“We wound up getting them from Taiwan, from people we’d never met or dealt with before but who could accept a SolidEdge CAD file.” But transport times from Taiwan negated the sought-for rapid prototyping gains. The solution? The acquisition of an NC milling machine, equipped with a serial port.

“It took us six months to master, but we finally got there,” concludes Wood.