Aircraft are running more safely and efficiently than ever before. A critical aspect of the aerospace industry that often goes unnoticed, but plays a vital role in ensuring the safety and reliability of aircraft, is the inspection of aerospace components. Lufthansa Technik Turbine Shannon (LTTS) specializes in the repair of components for both high-pressure turbines (HPT) and low-pressure turbines (LPT) for CFMI and GE aircraft engines. These high-value components work cohesively to ensure aircraft function correctly, and transport passengers and crew safely to their destination. Repairing these essential parts not only leads to potential cost savings of up to 80% for airlines but also extends the aircraft’s useful lifespan.

HPT shrouds are located in the turbine section, where temperatures can reach several thousand degrees Fahrenheit, and pressures exceed hundreds of pounds per square inch. Therefore, the components are often subject to considerable wear and tear due to the extreme operating conditions.

Repairing HPT shrouds involves a process that requires re-establishing sealing slots (0.5mm wide) on the end of the part after weld or braze repair by EDM (Electro Discharge Machining). The tolerance on the location of the slots is 0.25mm.

LTTS faced several challenges with their traditional inspection method for HPT shroud repair. Their process involved using hard gauge fixtures under 4X magnification to inspect the slot location. According to Product Engineer for LTTS, Patrick Crowe, “This process was tedious, susceptible to parallax error and only verified the slot in the maximum permissible position.”

A new inspection method was required in order to improve accuracy and aid the optimisation of the automatic EDM set-up process to target nominal slot location during machining.

OMNI digital microscope and measurement system was deployed to ensure greater accuracy for the inspection of these high-value parts. By using calibrated photomasks and graticules, the tolerances for the slot location were set. A machined part can now be taken directly from the EDM process and loaded under the OMNI to quickly and accurately verify that the location of the machined slot is correct.

This advanced method of inspection aided the development speed of EDM programs for new part types, by enabling the collection of measurements and feeding the data directly into machine offsets.