Today’s aircraft propulsion systems are wonders of technology. Aircraft industry suppliers are modernizing production technology to meet the challenge of rapidly growing demand for global air travel. Above all else, the blades in the hot gas area of the engines have to withstand loads that, until fairly recently, seemed uncontrollable.
To meet the challenge, MTU Aero Engines turned to a team of suppliers including Liebherr, Blohm, AMT and SOFLEX to achieve “the highest degree of accuracy required when machining high precision blades for turbines,” according to Marc Weiss, senior manager, flexible production systems at MTU Aero Engines, Munich, Germany. The company is a manufacturer of civil and military aerospace propulsion systems in all performance classes as well as stationary industrial gas turbines.
Turbine blades are cast parts, usually made of nickel-based alloys that are difficult to cut. Complex geometries need to be machined with precision. During operation, the blades have to endure challenging conditions, including tremendous centrifugal forces, temperatures close to metal melting points and heavy vibrations. A break could lead to destruction of the power plant. For this reason, strict quality requirements apply for all steps of the manufacturing process.
For the development of a new, highly automated production system, MTU Aero considered only partners that were able to guarantee the highest level of quality and reliability. “The requirements of MTU were extensive and necessitated more than a tenfold increase in staff productivity,” said Michael Appel, regional sales manager for automation systems at Liebherr-Verzahntechnik GmbH in Kempten, Germany. Productivity had to be increased substantially in order to meet the growing demand. For example, in the past, one employee was needed to manually operate one to two machines in a production chain of individual stations. In contrast, the new solution relies on just one employee to achieve high processing depth at four parallel-operating, fully-automatic grinding cells.
Each cell consists of a PROKOS XT six-axis grinding machining center from Blohm Jung GmbH, Hamburg, Germany, which is supplied by a robot from AMT Alfing Montagetechnik GmbH, Aalen, Germany. The robot receives workpieces, clamping fixtures, dressing tools and gripper tongs from a fully-automatic Liebherr pallet handling system (PHS). Equipped with 250 pallet slots, the PHS can supply the machining centers for at least 66 hours unattended to allow the systems to work through a complete weekend, as well as with flexitime operation. A loading portal (LP), also from Liebherr, runs on the other side of the manufacturing cells and supplies the machines with tools and grinding discs.
The “brains” of the outfit is a control system from SOFLEX Fertigungssteuerungs-GmbH, Rottenburg, Germany, which networks all of the plant units together and enables self-organized production. This new flexible production system can machine a mixture of about 15 different component types in any number required. Moreover, the workplace for the machine operators has also been laid out in a disabled-worker friendly manner.
Blohm Jung GmbH is part of the United Grinding Group and services the aircraft turbine industry. The systems used at MTU have six axes and a rotary swivel table with a zero-point clamping system, a profiling station with diamond-tipped dressing rolls for the grinding bodies and a toolchanger for grinding wheels, drills, hobbing cutters and measuring probes. The machining software used was specially developed by MTU.
The AMT robots used in the individual cells perform a difficult task. AMT is an installation and fittings specialist with extensive experience, including in the automotive industry. The robots must remove the individual blades from frames, place them in a special clamping fixture with precision and then clamp them together with a fitting. The clamping fixture, including the clamped part, is then transferred to the grinding center where it is fixed using a zero-point clamping system. This operation is difficult and requires a great deal of expertise with regard to both the transfer and the sensitivity of the fitting operations. The turbine parts must be treated as carefully as raw eggs here because even the smallest damage or scratches on the surface would be unacceptable.
A control system from SOFLEX is used for the manufacturing control. This digitizes, networks and organizes people, machines, systems, logistics and products directly with each other and optimizes the entire value chain up to the fully automated provision of workpieces and operating equipment. The software plans and organizes order processing; controls workpiece throughput and the provision of tools, NC data, clamping fixtures, and other elements; and transmits the required manufacturing information to the processing machines or the manual workplace. At the same time, the system acts as a link between manufacturing and higher management levels by automatically exchanging information with the other IT structures in corporate planning via ERP, CAD/CAM and PDM systems.
“The actual challenge for Liebherr was to select our modular automation components in such a way and to link them with the other systems in such a way that a smooth interaction was facilitated,” Appel explained. Liebherr also took on the responsibility for CE certification of the entire system. Cooperation in the engineering team was coordinated by MTU. The partner organizations worked on equal footing as a team. They exchanged ideas and developed the decisive characteristics of the system. This also included details like an auxiliary function for the operator where a laser pointer indicates the position to which the next part to be sorted belongs.
“The system that we have created together is complicated and more advanced than the technology employed to date,” said Marc Weiss. The ramp-up of the overall system went successfully and the results so far have met the planning specifications. With the new system, MTU considers itself to be well equipped for the requirements of the future and the expected shortage of skilled workers.
The Liebherr Automation Systems product division is part of Liebherr, a specialist in automation solutions. Projects can be implemented in all areas of manufacturing and installation with a wide range of products such as linear gantries, pallet handling systems and conveyor systems. In cooperation with well-known machine manufacturers, the Automation Systems division implements line linking, automation of machining centers and system integration of machine tools.
For more information from Liebherr Gear Technology and Automation, go to www.liebherr.com or phone 734-429-7225; from United Grinding North America, go to grinding.com, or phone 937-859-1975; from Alfing Corporation, go to www.alfing.com, or phone 734-414-5884; from SOFLEX,
go to soflex.de, or phone +49-7457-9455-0