Munich-based MTU Aero Engines develops, produces and supplies components for civil and military aircraft engines, as well as for power generation gas turbines. It is a primary supplier to US manufacturer Pratt & Whitney, whose PW1100G-JM geared turbo-fan (GTF) engine is one option for powering the new Airbus A320neo.
MTU is always researching innovative materials and production processes to achieve benefits in cost, weight and function, while maintaining safety. This approach is essential in the aerospace industry, with aircraft manufacturers looking to significantly increase the efficiency of their next-generation aircraft. For example, Airbus is aiming at a 15% reduction in fuel consumption for the A320neo, compared with its predecessor.
MTU currently operates seven additive-manufacturing (AM) machines from EOS, which has a UK subsidiary in Warwick (
www.eos.info), and it has started using them for the series production of nickel alloy borescope bosses. These form part of the turbine housing for the A320neo’s GTF engine and allow the blades 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.
They 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. This method was originally used for the rapid manufacturing of prototypes, but it is increasingly used for manufacturing components in significant quantities.
Immediate benefits
The 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 bore-scope 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.
On-line monitoring captures each individual production step and layer. In addition, new quality-assurance procedures were introduced, including optical tomography — and the German Federal Aviation Authority has certified the EOS manufacturing platform.
Karl-Heinz Dusel, director of rapid technologies at MTU said: “About 10 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.”