3-D printing in aviation

3-D printing, the process of printing a tangible structural element, is common within a variety of fields: you can find it in dental replacements, artificial hip-joints but also for manufacturing tools.

Until now, parts manufactured using 3-D technology have been unable to compete with traditionally made components. But that is rapidly changing - especially within the realms of the aviation industry where weight is a major consideration when it comes to manufacturing.

Concept Laser, a German company, is at the forefront of high-quality 3-D printing. The fledgling company was responsible for building the first such printer capable of producing real components with a method called Selective Laser Melting (SLM).

Melting, rather than sintering

With that, it was made possible to use common industrial alloys, like steel or titanium in 3-D printing. Before the advent of the SLM, there were 3-D printers on the market, but they only had the capabilites to sinter rare and uncommon alloys in a process similar to that used during the production of ceramics. But the end product was not very durable.

In order to properly melt the metal, inventor and company founder, Frank Herzog, had to overcome several hurdles. He needed to develop a means of circumventing the problem of tension build-up within the metal during the melting process which ultimately led to components cracking.

"I watched a toolmaker welding," he recalls, "he did not do one continuous weld, but several shorter ones. This was to prevent his work from coming apart." It was then he had the idea to change things up a little bit - "my own idea was to change the exposure of the metal powder to the laser light so that the energy would be more evenly distributed."

Rather than melting the powder in one continuous line, Herzog decided the laser would work randomly. With that he determined numerous tiny sections, each of which was exposed to laser light only very briefly. But that required huge amounts of data - and back then, computers were not that powerful.

Too much data

"It took me two to three weeks and numerous system crashes to get the data loaded into the machine. The component we wanted to print was huge - normally this would never have worked. After two days of printing, I opened it up and it was completely free of cracks. That was a Eureka moment, and I registered my first patent," Herzog explains of his innaugral invention.

The inventors' next hurdle was to improve the homogeneity of the material, since the printed parts were often still quite porous. Herzog wondered if it was due to the wavelength of the CO2 laser machines, which were common in those days. Fortunately for Herzog, his girlfriend (who later became his wife) had purchased a more modern solid-state laser with a shorter wavelength for her family business.

"We thought shorter wavelengths would penetrate the material much better," Herzog recalls. "Then we ran some test exposures and found out that the laser was able to completely melt the alloy."

The real deal

Herzog's discovery revolutionized 3-D printing. From now on, it was not only about producing prototypes but really durable components and tools. In 2001, at the Euromold Trade Fair in Frankfurt, Herzog presented his company and his first printer.

In the 14 years that have followed, he has been flooded with requests from the industry. Today, Concept Laser covers about one-fourth of the world market in SLM 3-D printers, and is constantly developing better and more powerful machines.

Bionics improves products

Meanwhile, in Hamburg, Professor Claus Emmelmann has made SLM a main focus of his work at the Technical University. Emmelmann also founded the Laserzentrum Nord (LZN) - a company that functions as a bridge between university education, applied research and business.

Heading into the large factory hall, the professor comments on the center's design principles - which includes product components for aviation, medicine, tools and engineering.

Holding up an example of their work, Emmelmann points to a complex, but quite elegant looking bundle of pipes.

"It weighs just 20-percent of a conventional manifold. We do not have to drill holes into it, therefore the pipes can be formed to accommodate the actual hydraulic pressure." This, the professor adds, enables them to reduce pressure loss by 50-percent. "This component is not just lighter, but also more efficent."

Less susceptible to interference

3-D printing gives engineers options they did not dare dream of before. The added bonus, the technology is ideal for aviation. Professor Emmelmann found the ideal partner in Peter Sander, an engineer at Airbus' R & D department.

Open call for ideas

Sander didn't hesitate. "One year ago, we started a campaign and told everybody: 'We will be able to print in about one year. We are looking for solutions that reduce complexity, weight or shorten the production time - anything we can achieve by 3-D printing." That was Sanders' open call for ideas at Airbus to find out what was possible. "Within five weeks we had 192 proposals on the table," he recalls.

Of those, Sander selected 13 finalists. "Those teams showed to the top management what they'd discovered. And everyone was blown away - there were components nobody had even imagined were possible."

In 2016, Airbus will launch its SLM series production through its 100-percent subsidiary, called Premium Aerotech. For Frank Herzog, this means a new era in the rapid development of his company - Airbus will soon need more, faster, bigger and more powerful machines. And the young company founder is determined to deliver, "we have grown as a company only because the industry continuously presented us with new demands - and we always took up the new challenges."

The next challenge - stemming from the series production of Airbus - is called: Automation. So far all printed components need to be taken out of the machines, cleaned, and the quality controlled by hand. In the future this will be done by robots - welcome to the future factory.

The three laser printing pioneers - Herzog, Emmelmann and Sander have been nominated for the German Future Awards, which German President Joachim Gauck will award in a ceremony on December 2 in Berlin.