In a development that’s been hailed as a major step forward in the use of additive manufacturing to produce critical functional components, engineers at Siemens have completed full load engine tests for additively produced gas turbine blades.
Subjecting the components to 13,000 revolutions per minute and temperatures beyond 1,250°C the company successfully validated multiple AM printed turbine blades with a conventional blade design at full engine conditions, and also tested a new blade design with a completely revised and improved internal cooling geometry.
The tests were carried out at Siemens’ industrial gas turbine factory in Lincoln, and used blades manufactured at its newly acquired company, Worcester based 3D printing specialist Materials Solutions.
The blades, which were installed in a 13MW Siemens SGT-400 industrial gas turbine were made out of a powder of high performing polycrystalline nickel superalloy. This allowed them to endure high pressure, hot temperatures and the rotational forces of the turbine’s high-speed operation.
At full load each of these turbine blades was travelling at over 1,600km/h, carrying 11 tons or equivalent to a fully loaded London bus, surrounded by gas at 1,250 °C and cooled by air at over 400 °C.
“This is a breakthrough success for the use of Additive Manufacturing in the power generation field, which is one of the most challenging applications for this technology,” said Will Meixner, CEO of the Siemens Power and Gas Division.”
Meixner added that the breakthrough will help Siemens accelerate the development of new gas turbine designs. “This new flexibility in manufacturing also allows Siemens to develop closer to the customer’s requirements and also to provide spare parts on demand,” he added.
GE mixes lasers and water to keep turbine blades cool during drilling
Turbine blades for use in jet engines need to be made of a hard, unyielding exotic material made to exact specifications, which means the drilling of tiny cooling holes in the blades runs the risk of ruining them. To prevent this from happening, GE is combining the heat of the laser beam with the cooling of the water jet to drill holes without weakening the blades.
The inside of a jet turbine is a material engineer's nightmare. With temperatures approaching that of molten steel, incredible pressures, and roaring with hot corrosive gases, the turbine's parts, particularly its blades, need to be made of exotic alloys or ceramics to ensure they are protected against damage and remain within the painstakingly precise tolerances of their design. To achieve this, engineers drill tiny holes and channels in the blades to allow cooling air to circulate.
The trick is to drill the tiny holes without damaging the material in the blade. Lasers can cut very precise holes by vaporizing the material on the spot, but they also heat the surrounding metal, which can change the molecular structure and weaken it or make it more susceptible to corrosion from the hot gases. Worse, the vaporized metal can fall back as droplets that can stick to the blades. The trick, therefore, is to cut and cool at the same time.
GE has carried this trick off thanks to a laser/water jet hybrid called Laser MicroJet, which was developed by the Swiss company Synova and adapted by Charlie Hu, an industrial manufacturing engineer at GE Power & Water since 2011.
"We had to redesign the laser jet to the geometries we required," says James Cuny, engineering executive at GE Power & Water. “Before this, the machine used for other applications was like a big barrel with a laser coming out of it. It was not very conducive to what we required.”
The MicroJet, combines the laser with a hair-thin water jet, but the water is more than a coolant. It also works like an optical fiber that guides the laser to its target, so both jet and beam hit the exact same target. The water can then cool the area around the new hole while washing away the debris before it can settle. According to GE, this not only reduces the damage caused by the laser drilling, but also makes the turbines more durable and capable of greater speeds.
GE says that the success with drilling turbine blades has led the company to look at other applications of the technology in aviation and other areas. As part of this, Hu, GE, and Synova are looking at combining the laser with a water jet with a high enough pressure to cut steel to produce a double-edged cutting device.
Siemens team unveils 3D printing spider-bots
Developed by a team at Siemens Corporate Technology’s Princeton campus the devices – dubbed SiSpis – are the latest step in the development of autonomous mobile manufacturing techniques that Siemens’ believes could ultimately play a major role in the manufacture of everything from aircraft to ships.Engineers at Siemens Corporate Technology lab are interested in mobile autonomous manufacturing
“We are looking at using multiple autonomous robots for collaborative additive manufacturing of structures, such as car bodies, the hulls of ships and airplane fuselages,” said Livio Dalloro who heads up the group behind the systems.
Designed and built almost entirely in-house, and underpinned by a modified version of Siemens’ NX PLM software, each spider is equipped with an extruder similar to those found on traditional 3D printers, that prints a cornstarch-and-sugarcane substance known as polylactic acid.
Each robot is equipped with an onboard camera and laser scanner that enables it to interpret its immediate environment. Knowing the range of its 3D-printer arm, it will then autonomously work out which part of an area can cover, while other robots use the same technique to cover adjacent areas.
Thanks to algorithms that allow multi-robot task planning, two or more devices can collaborate on the additive manufacture or surface processing of a single object or area. And by dividing each area into vertical boxes, the robots can work collaboratively to cover even complex geometries in such a way that no box is missed.
Intriguingly, because the spiders always know where they are, a device is able to autonomously find its way back to a charging station when its batteries are low. But not before transmitting a progress report to a recharged spider that is able to pick up where its colleague left off.