At the Berlin Air Show (May 20 to 25), Germany's Fraunhofer Institute for Production Technology IPT and the Fraunhofer Institute for Laser Technology ILT will be showing several components that have been produced or repaired with the help of additive manufacturing.
To illustrate what the new process chain based around selective laser melting (SLM) can achieve, the pair has produced a nozzle guide vane (NGV) cluster that comprises six double vanes. Previously, the vanes for turbines could only be produced in pairs. Now they can be installed much more easily and quickly.
In addition, for the first time, a honeycomb structure is now feasible, with the entire component about 30% lighter as a result. "We combine subtractive, subsequent milling with additive SLM," explains Dr Thomas Bergs, managing chief engineer at the IPT.
The research is a sub-project of the Cluster of Innovation AdaM, short for 'Adaptive production for Resource Efficiency in Energy and Mobility' – in which the Fraunhofer Institutes IPT and ILT, as well as 21 industrial partners, pool their skills. The goal is to technically implement new concepts for turbo machinery – for engines, among other things – so that they can convert energy more efficiently. Furthermore, CO2 emissions are reduced and resources conserved.
Repair or parts is also important, however. As part AdaM, the researchers have also considered the maintenance, repair and overhaul (MRO) of engine blades. While technicians previously had to repair these blades manually, the process is now fully automated. "We do not even need half the processing time. And more importantly, the method is reproducible and ensures high quality repairs," says Dr Bergs.
An important step toward automation was the development of the 'CAx framework'. This software approach allows all the various repair technologies to be operated from a single platform. 'CA' stands for computer aided, "x" for the individual technologies of the production. First, geometric data of damaged or worn-out blade is acquired by digitising. Second, a milling machine blends out the defect and, third, laser radiation builds-up the blade again layer by layer via Laser Material Deposition (LMD). The researchers have already implemented this method for gas turbines; now, they can also transfer it to engine blades.
At the ILA trade show, the researchers will show both a repaired helicopter blade that is approximately six inches wide, as well as the 3 m blade of a Transall aircraft. Additionally, they will present a new manufacturing method for blade integrated disks (blisks). This involves heavy duty compressor stages where the individual blades have been milled from a single piece. The result is aerodynamically improved and lighter, the researchers say.
Author: Andrew Allcock