May 3 2005
It is often better to repair damaged machine parts rather than replace them. Turbine components are restored to service condition by means of laser-beam deposition welding. This technique, along with many other rapid processes, will be presented at the Euro-uRapid Conference.
Like all machine components, the rotors in turbines and aircraft engines have to cope with many and varied physical stresses and strains, and these tough demands eventually take their toll. In a new design referred to as the “bladed disk” (blisk), the rotors are no longer made up of several parts, but for reasons of strength, compactness and cost-efficiency are produced in a single piece. If, however, the blades become very worn or are damaged, perhaps by bird impact, they can no longer be simply removed from the disk and replaced. “A new blisk typically costs 35,000 to 60,000 euros,” explains Steffen Nowotny, who heads the Thermal Coating Processes department at the Fraunhofer Institute for Material and Beam Technology IWS. “It is six to seven times cheaper to repair the blisk using direct metal deposition, a technique based on laser-beam precision build-up welding. This repair method is gaining ground in the aviation industry – in car manufacture it has already become a standard technique for restoring forming tools to working order.”
Laser beam build-up welding is one of the many generating methods now applied when one-off items or small series are produced or have to be individually repaired. The first step in the repair of a damaged component using this technique is to conduct a three-dimensional scan. A computer program then compares the part’s dimensions with its original measurements and computes what is missing. A software system developed at the IWS guides the path of the laser as it welds on titanium-alloy powder and reconstructs the damaged area with layers of metallic beads. The entire process chain is a closed cycle and runs automatically from data collection followed by welding to finish-machining.
Nowotny is presenting a paper on the use of this repair technique at the Euro-uRapid. In its sixth year, the international conference for users of rapid technologies will take place from 10 to 12 May in Leipzig. Its coordinator Rudolf Meyer sums up: “The focus will be on new and efficient solutions for individualized products in industry, medicine and medical engineering.” The head of the Fraunhofer Rapid Prototyping Network has gathered together a group of speakers from within the network’s own ranks, who will be joined by experts from major international companies such as Boeing, Volkswagen and Whirlpool. Along with service providers and research engineers, they will present current trends and approaches, as well as explaining the need for action and cooperation in the field of rapid technologies.
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