By Henry Canady | AviationWeek.com
Optomec is steadily improving the performance and cost of a 3D printing technique well-suited to repairing metal parts on aircraft.
The company began working with Sandia National Laboratories to commercialize its Laser Engineered Net Shaping (LENS) technology, Senior Program Manager Tom McDonald says. LENS is powder-fed additive manufacturing. More common additive techniques accumulate thin layers within a powder bed to build up metal parts and accurately achieve fine features, but are typically limited to a cubic-foot work envelope and build very slowly.
In contrast, LENS’s directed energy deposition (DED) process uses blown powder and a laser beam, both focused on the same point. “It allows free-form fabrication, can be used on contoured surfaces and is uniquely qualified for repairs,” McDonald says. LENS also works with much larger sizes, up to 3-by-3-by-5 ft. in one Optomec machine.
LENS is important because it can repair metal parts that now have to be scrapped because tungsten inert gas (TIG) and other conventional welding techniques impart too much heat. This results in a large heat-affected zone that is too soft, brittle or distorted.
Many metal repairs are made to a very small portion, perhaps a quarter-inch dent, wear or defect a few thousandths of an inch in depth— in much larger parts, for example a bearing and/or seal 5 to 20 in. in diameter. The defect compromises the function, but not the structural integrity, of the expensive part, but must be repaired effectively or thrown away.
McDonald says LENS-type processes are used now to repair blade tips on commercial engines. The Defense Department is also very interested in them for repairing high-priced titanium and nick-alloy engine parts. LENS repairs can cost “far less than half” of new parts and reduce repair turn times as well. In some cases, LENS can repair a damaged part with a higher-performing metal to make it more resistant to wear or corrosion.
LENS repairs have traditionally been done in glove boxes to limit ambient oxygen to less than 10 parts per million. Optomec is now fitting LENS on conventional Computer Numeric Control (CNC) machine bases. This enables hybrid production of parts by both subtractive and additive methods. LENS can now do repairs, add features to parts and produce new parts from scratch on a single machine.
Optomec is also reducing machine costs, to as little as $250,000 for an open-atmosphere LENS machine and $400,000 for its latest glove-box hybrid machine.