Additive manufacturing: Layer by layer
3D printed into highly complex structures, extremely light and incredibly stable. The small Munich suburb of Krailling represents the success story of additive manufacturing like no other place on Earth.
11.2015 | Text: Thorsten Rienth
Thorsten Rienth writes as a freelance journalist for AEROREPORT. In addition to the aerospace industry, his technical writing focuses on rail traffic and the transportation industry.
In the mid-1980’s, Dr. Hans J. Langer was working for an American company and, while visiting a customer, saw how its engineers were using liquid photopolymers to produce plastic parts layer by layer. The energy required for this process came from a laser. Langer was astounded. What if this process could also produce functional components? “The image of a bird bone came to mind—a complex hollow body that is nevertheless strong and light.”
Langer spoke with the company’s senior management. He proposed entering a world that he called electro-optical systems, or EOS for short. Technology was the next logical step in the company’s evolution, he explained. Instead of producing just components, it had to be possible to use lasers, ultrafine metal or polymer powders and the right software to manufacture complete systems. Senior management declined, but the Munich-based physicist couldn’t get the idea out of his head. He looked for and found an investor, gave his notice and branched out on his own. Twenty-five years later, Langer is CEO of the EOS group. Headquartered in Krailling, near Munich, EOS is the world leader in technology and quality for high-end additive manufacturing solutions.
Limited only by creativity
The display cabinets in the company’s showroom narrate how the company got to where it is today. It all began with model helicopter housings, connectors and robot grippers. Over time, products became increasingly sophisticated. The last of the display cabinets contain objects that look like sponges, but that are made of metal; highly effective heat exchangers that accommodate unprecedented surfaces in a volume of a few cubic centimeters; a small build platform on which up to 450 dental crowns and bridges customized for individual patients can be manufactured in one production run. The possibilities for application are limited virtually only by customer creativity. Examples range from a robot whose gripper simulates an elephant’s trunk to a toy manufacturer’s hollow mold cores that can be cooled much faster because the cooling follows their contours, doubling production throughput time for these parts.
However different the end products may be, they all have one thing in common: producing them using conventional methods would be considerably more costly, if it is even possible at all. EOS calls its method laser sintering. Since this technology can be used to process existing―and therefore already approved―materials, it was practically predestined for the aerospace industry, as well.
A laser builds components layer by layer
From a technical perspective, laser sintering involves three-dimensional micro welding techniques. Instead of milling workpieces from solid blocks, thus removing material, the powder-based EOS machine builds them layer by layer from metals, plastics or composites. A coating machine gradually applies very thin layers to the build platform. A powerful laser melts the powder at the precise locations specified by the computer-generated component construction data, and joins it with the layer below. The component is thus constructed additively―that is, layer by layer. In the most extreme case, each layer of metal has a thickness of just 20 micrometers, or 20 thousandths of a millimeter.
Almost any shape that can be designed with a 3D CAD program can be produced using this method. Design-driven manufacturing, where design dictates the production process, is edging out conventional methods where manufacturing sets the design limitations. This new approach allows for highly complex structures with delicate details, small batch sizes at acceptable unit prices, and highly customized products.
General functional principle of laser-sintering
The process behind it almost seems like a game. The laser hops across the powder like miniature fireworks in fast motion. “But it’s much more challenging than it looks―there are millions of weld joints involved,” explains CEO Langer. It’s not enough to just feed the machines with data and wait until the finished component comes out a couple of hours later. “It requires a lot of experience and a clear understanding of what factors influence the component quality and how they can be adjusted accordingly.”
A look at EOS’s figures shows just how fast this technology is growing. The company is aiming for more than 240 million euros in revenues in 2015. It would be the second consecutive year in which EOS grew more than 40 percent in one year. In the current year alone, the number of employees has increased by about 100, to some 740 worldwide. They work practically around the globe: in the U.S., China, Finland and Italy. Following the 2014 completion of the Technology and Customer Center, EOS is now building another new structure in Krailling. Langer estimates that his company will sell and install over 1,500 systems for its customers in the next three to five years―almost exactly as many as it has sold throughout the company’s entire history, from 1989 to today.
New headquarters of MTU’s partner EOS GmbH in Krailling near Munich.
Additive manufacturing of a guide vane cluster at MTU Aero Engines.
Additive manufacturing of a guide vane cluster at MTU Aero Engines.
From “rapid prototyping” to volume production
The origins of industrial 3D printing lie in “rapid prototyping,” the building of visual and functional prototypes. In times of shorter and shorter market cycles, the importance of faster production development and market launch is growing. 3D print engineers are no longer the stereotypical nerds who wear thick horn-rimmed glasses and tinker on futuristic devices. This technology is finding its way into volume production.
There is hardly a major industry player whose production facilities don’t include machines from Krailling. The Munich-based automotive manufacturer BMW, for example, was one of its first partners. EOS likewise works closely with Siemens, and there are also some EOS machines in operation at MTU Aero Engines in Munich. The first one went into operation in 2009―one of the first to ever be used in the aviation industry. MTU initially used it in toolmaking, for instance for coolant injection nozzles, grinding wheels and attachments with complex internal structures.
“Our focus was not initially on producing engines quickly,” explains Dr. Karl-Heinz Dusel, who is in charge of additive manufacturing activities at MTU. “We wanted to understand the technology from the beginning.” MTU now uses additive manufacturing to produce borescope bosses for the A320neo engine PW1100G-JM. “Seal carriers with integrated honeycomb seals are the next components we intend to use this technology for,” indicates Dusel. Here you get to know more about "Production parts made by laser melting."
Inside MTU Optical tomography
When it comes to quality issues, there can be no compromises in the aviation industry. To ensure quality as effectively as possible in components produced by additive manufacturing, MTU Aero Engines and EOS GmbH developed, as part of a strategic partnership for quality assurance, a new kind of quality assurance tool for metal-based additive manufacturing. The first result of this partnership is an optical tomography (OT) method developed by MTU that enhances the modular EOS monitoring portfolio. In addition to numerous sensors that monitor the general system state, the camera-based OT technology checks the exposure process and the melt behavior of the material at all times to ensure optimum coating and exposure quality.
Reproducible quality and process stability
As is so often the case, both sides benefit from the partnership. “From our perspective, it’s incredibly important to work with someone who truly understands additive manufacturing,” says Dusel. Merely producing prototypes isn’t enough. “For volume production, reproducible quality and process stability are crucial.” In other words, precisely the same concepts that are essential for EOS. “For us, it’s about mastering design principles,” explains Felix Bauer, Business Development Manager Aerospace at EOS. “Only when we have achieved that can we develop processes that create genuine added value for industry.”Is industrial 3D printing the new industrial revolution? Bauer shakes his head. “We won’t replace today’s manufacturing processes, but with additive manufacturing, we offer an additional option―it’s a matter of what the best choice is for a given application.” This will require some creative rethinking among engineers, companies and universities. Bauer likes to tell the story of a professor who, following a presentation Bauer gave a few years ago, sheepishly admitted: “I recently failed a student because he designed something that couldn’t be produced using conventional manufacturing methods―it would have worked using an additive method.”