Mobility

Selective laser melting in the production of aicraft engines

The aerospace industry, automobile manufacturers and suppliers use additive manufacturing. Boeing, for example, uses laser-sintered components in the 787 Dreamliner for a number of non-critical parts. Additive technologies also enable companies to produce spare parts for aircraft.

Researchers at the Fraunhofer Institute for Laser Technology ILT in Aachen, Germany, have shown in the EU project FANTASIA that even complicatedly shaped components of aircraft engines can be manufactured cost-effectively using selective laser melting (SLM). With SLM and other laser-based generative processes, 40 percent and more reduce throughput times for repair work. Up to 50 percent of the necessary material and at least 40 percent of repair costs can be saved in future.

"Additive processes not only make it possible to repair damaged engine parts perfectly, but also to manufacture complete components which in principle cannot be produced using conventional methods such as milling or casting," says Dr. Konrad Wissenbach of the Fraunhofer ILT. "This also enables geometries and designs to be created that were previously undreamed of".

However, the SLM process is not yet suitable for every turbine material. So far, the researchers have been working with Inconel 718, a nickel-based super alloy, and titanium alloys.

Metal components

The Fraunhofer researchers from Aachen are also opening up other materials for additive manufacturing: The Fraunhofer ILT scientists have shown that aluminum is suitable as a material for additive processes using the example of a valve made of AlSi10Mg.

In cooperation with an industrial partner, the engineers demonstrated that the manufacturing process for six series-identical functional prototypes could be reduced from 120 working days for die-casting to seven working days with the SLM process. The additively manufactured valves have at least the same mechanical properties as conventionally manufactured components. With individual characteristics, they even exceed these. The aim in qualifying a material for SLM is to achieve a component density of around 100 percent without cracks or bonding defects.

Aluminum alloys are used among othersin the automotive, mechanical engineering and aircraft industries. Up to now, selective laser melting has mainly used commercially available powder materials such as stainless steel, tool steel, titanium, aluminum, cobalt and nickel alloys. The processing of copper and copper alloys is difficult because the material conducts heat well.

The researchers at the Fraunhofer ILT have therefore integrated a laser system with 1000 watts of power into an existing SLM system. This makes it possible for the first time to additively manufacture components from various copper alloys with a density of 99.9 percent. The researchers are also working on the use of ceramic materials.

A further development of the process at the Fraunhofer ILT also makes it possible to manufacture objects from high-strength zirconium oxide (ZrO2)-/aluminum oxide (Al2O3) ceramic.

Metal powder injection molding and laser beam melting for the production of aircraft turbines

Dr. Ingomar Kelbassa from the Fraunhofer Institute for Laser Technology ILT won 2nd place in the 2011 Ferchau Innovation Prize under the slogan "Saving the GOOD - energy, material, raw materials" for a more efficient method of manufacturing aircraft turbines.

In order to accelerate the aircraft on the runway, turbines suck in air and blade wheels compress it. In the past, such blade wheels were manufactured by attaching the individual blades to the turbine discs.

Today, these components are made from one piece - similar to a stonemason who carves sculptures from a stone: A large block of material is milled to produce the desired component. However, much of the expensive material is lost in the process, leaving behind a pile of shavings - 80 to 90 percent of the material, depending on the component.

Dr. Ingomar Kelbassa, former head of department at the Fraunhofer Institute for Laser Technology ILT in Aachen, Germany, and his team have developed a far more efficient method of manufacturing aircraft turbines. "We don't remove the material, we apply it," reveals Kelbassa. The starting point is the turbine disk - on which the scientists grow the numerous blades, one after the other. The researchers apply the material to the disk via a powder nozzle. A laser beam melts it briefly on a surface of a few square millimeters. If the laser beam moves on, the material solidifies. Layer by layer, the scientists build up the shovel in this way.

The process itself has been around for some time - but Kelbassa has developed two changes: "We have been able to increase the deposition rates significantly; the process is 15 times faster than the standard two or three years ago. On the other hand, different material thicknesses can be produced more easily now. This is important for the turbine blades, because while they are two millimeters thick in the middle of the blade, they taper to less than one toward the leading and trailing edges".

Until now, it was only possible to produce different thicknesses in a roundabout way: several tracks were needed. The laser beam was focused so that it could process the thinnest point. If the material was to be applied in wider layers, the laser beam had to melt material several times next to each other. "We can adapt the laser beam locally, i.e. focus it further or more narrowly - a kind of zoom function," explains the prizewinner.

The Fraunhofer Competence Field Additive Manufacturing is a competent partner for application-oriented research in automotive and mechanical engineering. The technology of laser beam melting offers the possibility of direct manufacturing (Rapid Manufacturing) of components and tools (Rapid Tooling) for automotive engineering and motor sports.

Laser beam melting also allows the rapid production of sophisticated, highly complex, filigree components and systems without tools, which goes beyond the limits of conventional production technologies.

The range of services includes the production of prototypes made of metallic materials with serial properties, the development, design and manufacture of lightweight components with lattice or bionic structures, and the generative production of components and tools for serial use.

Intelligent rear wing

Together with Team Rosberg Engineering, the Fraunhofer IFF has developed an intelligent rear wing for a racing car in the German Touring Car Championship.

The present solution uses the special properties of additive manufacturing technologies and today's sensor materials: additive processes such as selective laser sintering are able to produce the wing geometries, which are characterized by a high proportion of free-form surfaces, with dimensional accuracy. The sensor components can detect, evaluate and subsequently actively control changes in environmental conditions such as pressure and temperature distribution or occurring vibrations and deformations.

Layer build-up processes enable a fast and flexible production of the highly complex aerodynamic components, so that the findings from the tests can be implemented in the geometric design of the wings within a very short time.