Additive Manufacturing Could Change Spare Parts Supply Chain

The Future Of Additive Manufacturing Is Particularly Bright For MROs

New technologies that promise a lot, but deliver little, are common. 3-D printing has recently emerged from 20 years of quiet development to sudden global awareness. Considering the many wild predictions made about its potential, one might assume it was another fad that cannot live up to its own hype.

Peter Sander is responsible for 3-D-printed metal-part projects at Airbus Emerging Technologies & Concepts. He has been at the forefront of this emerging technology—additive layer manufacturing (AM), its formal name—and has seen how rapidly it has developed. While speaking with Aviation Week, he was keen to stress the realistic, yet still considerable, expectations of AM over the more fanciful ones.

“If people think we will have a 3-D printer spooling out a complete aircraft in one shot, they are mistaken,” Sander says. However, weight reductions of up to 50% and new designs that drop parts counts to two from 163 are already a reality.

But AM is still largely known for the polymer creations that even weekend hobbyists are able to make, quickly and cheaply. It was such a part that Airbus used for its first trial of AM.

“Normally, with spare parts you have to maintain your pooling all the time, so the first part we did was a plastic seat bracket for an A300/A310 where the supplier was not available,” says Sander. “It is now installed and has been flying since February [for Canada’s leisure carrier Air Transat]. For that, we demonstrated a 75% lead-time and cost reduction, and since then, we now have several hundred plastic parts on our A350.

“For parts such as these, it makes sense to produce them near the place of consumption, because you can have a plastic printer on a final assembly line, printing brackets that will be used tomorrow, rather than printing thousands and keeping them in stock,” says Sander.

While polymer AM will create significant savings in cost and weight, what has lifted its potential further is a technique called selective laser melting, which works on metal. In this process, manufacturers apply successive layers of metal powder between 20-100-microns thick, and then weld the powder into place with lasers. This allows designers to create metal shapes that are impossible through older material-removal techniques, such as milling or forging, while also using fewer parts.

For example, this summer NASA used AM to construct a rocket engine igniter that traditionally took 163 parts to create. NASA produced the new AM-made part from only two. Similarly, Sander says one of the 50 projects underway involves taking a design requiring 200 parts down to three.

As well as being simpler in design, it also leads to significant weight reduction; a style Airbus calls Bionic, which looks more like something from nature, such as the bone of a bird—with multiple hollow chambers—than a solid chunk of metal.

“Of my projects, I have not realized anything lower than a 30% weight reduction, and I have made up to 55%,” Sander notes. “For airlines who are [operating very competitively], an aircraft that is half the weight is obviously very attractive for cost savings.”

Elsewhere, General Electric, in partnership with Safran of France, has used AM to make fuel nozzles for its next-generation LEAP engines that will be 25% lighter and five times more durable than their predecessors.

Pierre Letord, head of the industrial means division at Snecma (part of Safran), says: “We’ve already manufactured over 500 experimental parts, destined for the Silvercrest engine in particular, using 3-D printing. If the shape of a part needs to be changed, all we have to do is modify the CAD model. We no longer need to change the machining process for machined parts or rework the molds for cast parts. Development cycles are [also] considerably shorter.”

Likewise, Sander says, Airbus will start producing complex two-tubes-in-one fuel pipes by early 2016.

Individual parts are impressive, but Sander is particularly interested in the advances possible with system parts. “We will have our first hydraulic manifold—for steering—flying by the end of 2015, and made on an industrial scale by the end of 2016. After that, we will be working on bigger parts, such as flaps and spoilers.” 

Reducing design complexity 

is not the only advantage. Material-removal techniques involve milling parts from a solid block of metal, which can create up to 90-95% waste. By welding only precise amounts of metal powder, any leftover powder is simply collected and reused for another part.

While AM is just now hitting its stride in terms of return on investment, this minimization of waste still makes the cost of AM attractive for expensive metals, such as titanium, high-quality steel and aluminum. Sander estimates Airbus will be able to print titanium on an industrial scale by the beginning of 2016, with aluminum a year later, which will help reduce the costs further.

Pieces constructed using selective laser melting also require little tooling, which can provide impressive lead-time reductions. “For metallic parts, a lot of the production chain will change. You will eventually be able to remove about 50% of the old machinery and bring in printers that will create parts that are near end completion,” says Sander. “Afterward, you will still need nearly the same metallic chain, such as heat treatment, possibly surface treatment, and final rework with drilling, but the first half will be heavily reduced.”

For Sander, the end goal will be an aircraft manufacturing line that is similar to current automotive ones. “It’s amazing what the automotive industry has achieved. It has part lines that have different types of automotives on them. In 10 years, we will have the same,” he predicts, including additive parts that are then joined by robots.

“A Bionic aircraft will not have stringers and frames as we have today. We will print the notch where the stringer and frame meet and then we will weld on a sheet metal part. We will not have printers making an entire aircraft, but we will mix technologies that will give cost and weight reduction,” says Sander.

This has interesting implications for airlines: “Not only will these new aircraft be 33% lighter and their production will be quicker, but they will also be more individual,” adds Sander. “Currently, our industry is steered by available processes, because we have had to invest in large and expensive machinery. Because of this, we need to use a high level of reused parts,” explains Sander.

“But if I don’t need any tooling and I don’t need any stock, I can make one aircraft one day, and a completely different one the next, and, like automotives, I will be able to customize the products. This could be the next big step for our industry, where instead of having three variants of an aircraft, we have completely unique ones for each airline,” he says.

Terry Wohlers, an AM industry consultant and analyst, agrees that what is currently possible is only the beginning. “The industry has experienced impressive progress, but it has seen little more than the tip of the iceberg of what is possible.”

However, challenges remain. For example, only a few metallic powders are available. Safran says it is studying the properties offered by new ones, such as cobalt-chrome, titanium and nickel, but it remains to be seen how and when these influence what can be manufactured.

There is also the sophistication of laser welding, which is still in its infancy, but which Sander says is just as important for AM’s development. “When I started this work three years ago, we were using a 250-watt laser,” he said. “Today, you can buy 1-kw lasers, an increase of a factor of four, but also machines that have two lasers for 2kw.”

For further advances in lasers, Sander points to the German company, Concept Lasers, which produces a camera system, the melt pool module. This takes 10,000 pictures per second of the exact melting point of where the laser is welding the metal, allowing far greater control and precision of the welding.

“Today, we have the first cost-effective parts,” says Sander. “They are very expensive, but within two years the technology will be available, which means we can talk about end process control of the printing machines. Then we will be able to manufacture parts [at the same cost] as milled parts.

“This is the future, I’m absolutely sure,” he concludes. 

A version of this article appears in the October 6 issue of Aviation Week & Space Technology.

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