The (long) road to qualification

While parts are being flown on aircraft made from additive manufacturing processes, what are the challenges in getting the material flying. Justin Cunningham finds out.

here is no doubt, 3D printing is a cool technology. For sci-fi geek – myself included – it is a step towards the replicators seen in Star Trek, the creation of virtually anything in an instant. And while we are some way of that, it is for now a fascinating technology that's fast becoming a must have for designers and engineers alike.

But while many – again including myself – are excited by the prospect of 'having a play', the technology has been criticised for lacking clear application. People have found uses for them – for sure – but there is a disparity and nicheness of how they should be used usefully and productively.

You can always tell when a 3D printer is new to an office as it filled with Yoda heads, Eiffel Towers, and many other random plastic paper weights. Cool, definitely. The ultimate tool for procrastinators, perhaps. A tool that improves design, functionality, and time to market? Well that really depends who you talk to.

Additive technology continues a rapid rise in many markets, but it is still very much finding its way and seeking solid application by users who are figuring out how best to leverage it specific production qualities. A forerunner in making high end machines for professional use is Stratasys. The Israeli company has been building ties with big engineering industries for some time including automotive and particularly aerospace. The latter has been particularly interested in the capabilities on offer, which are a natural fit for its low volume, high value manufacturing processes.

And headway is definitely being made. Last month Stratasys announced that more than 1000 flight parts made on its Fused Deposition Modelling (FDM) 3D Production Systems were flying on the first-of-type Airbus A350 XWB aircraft.

A 1000 parts is significant, but it is unclear exactly what the parts are, other than they are being used for the interior. Afterall, 1000 tiny brackets to hold the food tray in place, for example, would be less impressive than 1000 different parts throughout the aircraft.

What is known is that the parts are 3D printed use ULTEM 9085 resin, which has been certified to an Airbus material specification and is also flame, smoke, and toxicity compliant for use on aircraft interiors. Again, that is significant. Getting any material certified for flight is not quick, easy or cheap. The upshot is that Airbus is obviously pretty certain that there is short term value in this kind of 3D printed process, as well as longevity for it going forward.

"Both companies share a vision of applying innovative technologies to create game-changing benefits," said Dan Yalon, executive vice president of business development, marketing and vertical solutions for Stratasys. "Our additive manufacturing solutions can produce complex parts on-demand, ensuring on time delivery while streamlining supply chains. Additive manufacturing also greatly improves the buy-to-fly ratio as significantly less material is wasted than with conventional manufacturing methods."

However, past these obvious benefits, there is also a downside. There is no doubt it is a great development tool for Airbus, but when it comes to production aircraft the throughput of additive machines seems to make the technology much less viable. Despite savings on materials and the all important buy-to-fly ratio, these are all mitigated by the fact that to 3D print a part takes a fair bit of time. So does the technology have a future in the aerospace industry beyond development?

"It doesn't surprise me that 1000 of these parts are flying, but I bet they aren't load bearing," says Kevin Cummins, the new CEO of GKN Aerospace. "We do primary structure, and that is where additive manufacture really works."

GKN Aerospace is making waves in the market with its titanium powder additive manufacturing process that it has been developing in partnership with Swedish based Arcam. And it is making no bones about the fact that it is fast tracking the technology for flight certification to get parts flying by the end of year. But the trouble is, how do you qualify additive processes that are, by their very nature, so changeable?

"You need to remove the variables," says Russ Dunn, senior vice president for engineering and technology, at GKN Aerospace. "We could take a whole range of different titanium's and then look at inconel, but we are concentrating on Electron Beam Melting (EMB) with the titanium 64. It's an existing material and we will get to the point of qualification on that. Will there be a further refinement that will be more attuned to a forging alloy? Of course."

As you expect, GKN has spent a number of years getting in to the real detail of how it should go through certification. The result is reams of data that paint a solid picture of not only process control, but the precise control of the properties within the materials itself.

"Any company in the world can buy a machine and make an additive component," says Russ Dunn, senior vice president for engineering and technology, at GKN Aerospace. "The real challenge is being able to certify the powder, the process and the part so every single component performs as required on the aircraft.

"So effectively we are doing belt and braces. And to gain customer confidence it means we are also going to part qualify."

Over the last three years GKN has done hundreds of physical tests in something it calls 'the hedgehog model'. The idea is simple, manufacture a hedgehog – or something with grain orientations in every single direction. And then test every single one through to failure. It is from this that GKN has been able to build up an enormous body of data that gives them evidence confidence – and statistical evidence – that no matter the orientation of grains in the material, it can produce properties that are predictable and within a tight tolerance.

"This is a clear part of our strategy, concentrate on one thing where there is a number of different applications, but remove variables, and then deliver," says Dunn. "Then build up where the technology is applied and grow the business."

The first step for GKN is to produce existing parts, using an additive process, that are essentially 'carbon copies'. The same weight, geometry and mechanical properties, but at 25% less cost. This is to establish the technology, and build up gradual capability in the market place.

While, the initial steps will effectively not do anything to optimise parts for the process, it is important for GKN to demonstrate more widely its ability to control this additive process. However, it will not be long before it look to refine the actual design of components to take advantage of additive manufacturing's ability to produce geometry like no other process. This not only means that weight of parts will be reduced, but also it will reduce part cost, as the cost is directly proportional to the amount of material actually laid down.

There is no doubt that GKN has the capability, desire and reach to make this happen, and happen in a major way. The company has a history of utilising materials and getting them in to industry, perhaps more than any other. If it does with titanium additive manufacture what is has for composites for example, then expect to be flown around on a 3D printed aircraft before long... Or, at least, one with 3D printed parts. And let's face it, that's pretty cool, isn't it?


Jet engine 3D printed... and it actually works!

Monash University researchers along with collaborators from CSIRO and Deakin University have printed a working jet engine in metal.

The engine is proof of concept that's led to tier one aerospace companies lining up to develop new components at the Monash Centre for Additive Manufacturing in Melbourne, Australia.

Microturbo (Safran) provided an older – though still in service – gas turbine engine. It's an auxiliary power unit used in aircraft such as the Falcon 20 and was chosen because Microturbo (Safran) was willing for the internal workings to be displayed.

"It was our chance to prove what we could do," says Professor Xinhua Wu, the director of the Monash Centre for Additive Manufacturing. "But when we reviewed the plans we realised that the engine had evolved over years of manufacture. So we took the engine to pieces and scanned the components. Then we printed two copies."

It was a challenge for the team and pushed the technology to new heights of success – no one has printed an entire engine commercially yet.

Professor Ian Smith, Monash University's vice provost for research and research infrastructure says: "This Centre allows them to rapidly prototype metal devices across a wide range of industries. It's part of a large integrated suite of facilities for research and industry at Monash."

The Centre, AMAERO and the jet engine project have been supported by the Australian government via the Australian Research Council (ARC), the CRC program, Commercialisation Australia, the Science and Industry Endowment Fund (SIEF); Monash University and Safran.

Author
Justin Cunningham

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