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Printing in three dimensions

21st May 2013


Prodrive used 3D printing to make 18 components for the Mini John Cooper rally car, and expects to increase this in future
The SAVING project says that a titanium seat buckle, made using 3D printing, could save £2m over the life of an aircraft
“It’s hard to tell fact from fiction," says Todd Grimm, president of 3D printing consultancy Grimm Associates
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3D printing promises to make short-run parts that are not economic using traditional methods, but potential users must watch out for hype. Lou Reade reports.

Techniques like laser sintering and stereolithography have come a long way since their early days as methods of prototyping. While still used to make models, they are increasingly employed to manufacture final parts.
 
Every market sector that relies on manufacturing – including automotive, aerospace and medical – is now using 3D printing to make components. And as materials and techniques improve, this is likely to increase.
 
Not surprisingly, the racing car industry has adopted 3D printing techniques to make short-run parts quickly and cheaply. Automotive consultancy Prodrive is using fused deposition modelling (FDM) to make parts for the Mini John Cooper rally car. The company began its adventure in 3D printing in a small way, taking delivery of a single Stratasys machine on a three-month trial. The first component that it made in this way was for an air intake system.
 
Paul Doe, chief designer at Prodrive WRC, told delegates at the TCT conference: “We wanted to try something new, but not expose ourselves to an expensive solution that did not work.”
 
This led to the creation of more parts, including an electronic driver display that indicates which gear the car is in. It must be connected up to other systems.
 
“We ended up with a part that could not be made in any other way,” he says.

The company had considered alternatives, such as using a carbon fibre composite – but Doe estimates this would have cost £300, plus a tooling cost of around £1600. The FDM-made part cost £45, with no tooling costs.
 
Prodrive also designed and built – in a few days – an aerodynamic housing for a microwave transmitter that streams pictures live on the internet. Later, there was an air engine intake that was made in four pieces and assembled. Then there was a thin roof vent deflector that brings air into the cabin, made by FDM and vacuum forming.
 
There are plans to extend this even further: while the 2012 version of the car had 18 parts made using 3D printing, this year’s model is expected to have more. In future, Doe estimates that each car will have more than 100 3D-printed parts.


 
Real deal
 
Luxury car maker Bentley Motors has relied on 3D printing for both prototyping and making short-run products.
 
“It helps to make a car look more realistic,” says David Hayward, studio operations & projects manager. “We use it to make wheels, and front and rear tail lights.”
 
The company has been using a 3D printing machine for nearly two years.
“It runs every day, and never stops printing apart from when it’s serviced,” he says.
 
The company installed a second machine, running at 95%, capacity, about a year ago.
 
3D printing has helped to expand design and manufacturing options at the firm.
 
“Design ideas had always been limited, depending on how they were going to be manufactured,” says Hayward. “The advent of 3D gives you fewer limits.”
Bentley produces 10 times more cars than it did 10 years ago, but Hayward says that 3D printing often makes more economic sense than soft tooling, depending on the size of the production run.
 
In prototyping, the company traditionally makes one-third scale clay models. Using 3D printing, it also makes one-tenth scale models – for both its own cars, and for competitor vehicles – before it gets to one-third scale.
 
“We can then make design changes very early in the process and re-cut them within a few days. We’re refining the design of the exterior very early,” he says.
 
Door mirrors, door handles and badges are examples of components that have been designed with a variety of different finishes, to make things as realistic as possible. At the end of the process, Bentley makes a full-sized model – made variously of clay and other prototyped parts – which can be very realistic.
 
The company made a drivable model for the 2012 Geneva Motor Show, which used rapid prototyping and 3D printing extensively. Fully working headlamps were 3D printed, as were grilles, interior parts and the central console.
“The one really challenging part was the wheel – which is multi-spoked and multi-vaned,” he says. “Every vane was made individually by 3D printing.”
 
Flying high

 
The aerospace industry has also recognised the benefits of 3D printing, and signalled its long-term aim to embrace the technology further. EADS, which makes Airbus, believes that aeroplanes might be made using enormous, factory-sized 3D printers by 2050.
 
The industry is already investigating the potential for these technologies: engine manufacturer GE, for example, recently acquired Morris Technologies – which has established itself as a specialist in the production of 3D aerospace parts.
 
Designers and suppliers are also keen to convince the industry of the benefits of 3D printing. One collaborative UK research project called SAVING – funded by the Technology Strategy Board – has investigated the energy-saving potential of 3D printing over conventional techniques. Early studies did not look entirely promising.
 
“We quickly realised that it is actually very energy-intensive,” says Mike Ayre, managing director of design agency Crucible Industrial Design, and a member of the project. “There’s no way you could call 3D printing processes ‘green’: it takes a lot of energy to melt titanium with a laser.”
 
However, he says 3D printing could save energy if used in the right way. “We could use it to save weight, and save energy and money in the long term,” he says. “We just have to accept that the parts themselves will be expensive.”
 
Ayre says that focusing on high volume parts will have the greatest effect. SAVING partners – and other researchers – have considered parts like clips, brackets, hinges and latches.
 
“Improving lots of parts, in a small way, can have a huge effect,” he says.

The partners decided that a belt buckle would be an ideal part to demonstrate 3D printing’s flexibility and weight saving benefits – and was easier to relate to than a complex engine component. It was designed to look like a conventional buckle, and used similar design principles. But it uses far less material (as non-essential portions can simply be removed), as well as opting for laser-sintered titanium rather than steel or aluminium.
 
“Titanium is easier to process in this way than steel or aluminium,” says Ayre.
 
The titanium buckle would weigh 70g, rather than 155g in steel. If a typical Airbus contains 850 of these buckles, the total saving would be 72.5kg – equivalent to 3.3m litres of fuel at a cost of around £2m.


 
It might appear that the saving is simply down to using lower-density titanium in place of steel, but Ayre believes that 3D printing has delivered two advantages over conventional techniques in this example.
 
“We can vary the wall sections at will, which would be very difficult with casting or pressing,” he says. “And the two components of the belt can be built in-situ, which means you remove the assembly cost.”
 
Phill Dickens, professor of manufacturing technology at Loughborough University, points to another aerospace example – a bracket for a TV set. A simple redesign can help to make the part thinner than before. But 3D printing can build it just as easily with an ‘internal lattice’ structure – so it is effectively porous. This offers huge weight savings, which has an effect for in-use costs.
 
“You could save around $880,000 if you used this on just 40 seats,” he says. “And that’s just one part.”
 
But he says that many practical issues must still be solved if 3D printing is to become a true ‘manufacturing technology’. These include: developing a broader range of materials; minimising process waste; and ensuring repeatability.
 
“There is also the issue of supports,” he says. “Supports are a real pain.”

 
The support is the structure that is built alongside the actual 3D printed part that must be removed after the part is complete. The best way to exploit 3D printing is to design ever more complex parts – which makes the issue of supports even more important. One possible answer, he believes, is to design the support into the structure of the part, so that it effectively becomes a part of the design.
 
“We have to do some really imaginative thinking to solve this,” he says.
Although we are still a long way from 3D-printed aeroplanes, blood vessels and moon bases, increasing numbers of designers and manufacturers are already making use of this flexible and powerful set of technologies.
 
Grimm tale

 
The take-up of 3D printing technologies has been huge. With the industry offering so much to manufacturers and designers, there is a danger that too much hype could confuse potential users, and prevent them from making informed decisions.
 
“It’s hard to absorb all this information, and tell fact from fiction,” says Todd Grimm, president of 3D printing consultancy Grimm Associates. “If you can’t tell them apart, that’s unsettling.”
 
He cites recent examples of where the technology has been over-hyped. Many stories about ‘3D printed planes’ failed to mention the 2050 arrival date, for example. At the same time, the new animated film Paranorman used 3D printing to create the faces of the characters – but this saved no time or money on the production.
 
Grimm says that 3D printing is a key technology for designers and manufacturers to adopt, but warns they must look carefully at the claims of each system – and each company selling it.
 
“Investigate, observe, listen – and question everything,” he says.

 One method is to target low-risk opportunities that are off the critical path. Then, if it fails, it can be treated as a learning experience, he says.
 
For all its promise, there are four ‘negatives’ that still need to be overcome, he says. First, there is no agreed name (is it ‘3D printing’ or ‘additive manufacturing’ or ‘rapid prototyping’?). Secondly, it encompasses a range of separate techniques – from stereolithography to fused deposition modelling.
 
“This makes it seem very wide and very shallow, which causes confusion,” he says.
 
But there advantages too: it complements high-volume techniques like injection moulding; it can make products of huge complexity; it can be very efficient because there are fewer steps involved, and less labour; and its flexibility means that designers can change their designs from one day to the next.


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