MTU Aero Engines, Munich, which develops, produces and supplies components for civil and military aircraft engines (as well as for power generation gas turbines), is a primary supplier to US manufacturer, Pratt & Whitney, whose PW1100G-JM geared turbofan (GTF) engine is one option for powering the new Airbus A320neo jetliner.
MTU is always researching innovative materials and production processes to achieve benefits in cost, weight and function, while maintaining safety. The approach is essential in the aerospace industry, with primes looking to increase significantly the efficiency of next-generation aircraft. Airbus, for example, is aiming at a 15% reduction in fuel consumption for the A320neo compared with its predecessor.
The Munich company, which currently operates seven additive manufacturing (AM) machines from EOS, has started using them for series production of nickel alloy borescope bosses. They form part of the turbine housing for the A320neo's GTF engine and allow the blading to be inspected at intervals for wear and damage using an endoscope, which in the aerospace sector is termed a borescope.
Previously, the bosses were cast, or milled from solid. It was the cost advantages of using EOS technology that was the decisive factor in adopting AM for this application, both in the development stages and in production. The Pratt & Whitney PW1100G-JM is the first aero engine to be equipped with borescope bosses produced by additive manufacturing.
The components are built layer by layer from nickel alloy powder that is melted by laser and allowed to harden so that each layer fuses to the one below. The method was originally used for rapid manufacturing of prototypes but is increasingly used for manufacturing components in significant quantities.
Advantages of the process include more design freedom as well as the possibility of using a wide range of raw materials, from light, flame retardant plastics to a variety of metals. Production requires less material and the tool-free manufacturing process considerably reduces lead-times.
Preparations for series production of the borescope bosses at MTU have now begun. Sixteen parts per build are envisaged, totalling up to 2,000 parts per year. The percentage cost saving compared to previously established manufacturing processes is expected to be in double figures and the quality level is already high. MTU and EOS are working together to optimise the finish of the component surface.
As MTU is a producer of raw materials, the company was able to develop a new process chain, which has been integrated into the manufacturing system. It is underpinned by a control system specifically developed by MTU. Online monitoring captures each individual production step and layer. In addition, new quality assurance procedures were introduced, such as optical tomography. The German Federal Aviation Authority has certified the EOS manufacturing platform.
Dr Karl-Heinz Dusel, director of rapid technologies at MTU says: “About ten years ago, we began using AM to produce tools and development components. To optimise utilisation of the capacity, we went in search of further areas where we could apply the technology.
"The borescope bosses for the low-pressure turbines of the A320neo's GTF engine were ideal for AM. They are small components riveted to the turbine housing that create openings to allow technicians to check the condition of turbine blades inside the engine.
“We see a lot of potential for the manufacture of further series components for aero engine construction, such as bearing housings and turbine airfoils, both of which need to meet the highest demands in terms of safety and reliability.”