Until now, manufacturing aero turbine blades necessitated the use of investment casting, electrical discharge machining, and multi-axis CNC milling. No longer. Researchers at the Fraunhofer Institute for Laser Technology (ILT) in Aachen, Germany, are building aircraft engine components using an additive method called selective laser melting (SLM). The researchers are part of the 6.5 million euro, EU-sponsored Fantasia project, tasked with developing near-net-shaped manufacturing methods and repair techniques for complex shape aero turbines. In operation, the components must endure extreme pressures, rotate 1,000 times/sec, and withstand temperatures up to 2,000° C.
SLM resembles selective laser sintering (SLS) except that it fully melts the metal powder while SLS just comes close to the melting point. Similar to other additive manufacturing methods, SLM involves digitally slicing a 3D CAD model into layers and then using this data to build physical parts layer-by-layer. The SLM machine applies a 30 to 100-micron-thick layer of metal powder to the substrate and a high-power laser beam immediately melts the metal into place. The machine builds the entire component by continuing this procedure for each layer, forming a permanent bond with the already-completed portion of the object.
To date, SLM works well with titanium alloys and Inconel 718, building components that are difficult to produce using conventional methods, says Fantasia lead Konrad Wissenbach of ILT. “For other fissure-prone aero materials, we are experimenting with preheating the construction platform and varying the laser parameters to prevent cracking,” he says. “To increase the build speed by a factor of ten, we are combining a large-diameter beam for large surfaces with a smaller-diameter beam for contours. In the future, SLM should cut the amount of material needed by 50% and slash turbine repair costs by 40%.”
Fraunhofer Institute for Laser Technology ILT, http://www.ilt.fraunhofer.de/eng/100000.html