Erosion of honeycomb structures used in aircraft engine components

HAESL, a joint venture between Rolls-Royce, SIAEC and HAECO, provides a service for the repair and maintenance of aircraft engines and components for many of the leading airlines worldwide.

HAESL has the capacity to carry out the complete repair and maintenance of the Rolls-Royce RB211 and TRENT series of engines, which are widely used in many of the aircraft currently operating. With an annual average of approximately 200 engines, HAESL has serviced more than 3,000 Rolls-Royce engines from the RB211 and TRENT series since its inception.

One of the operations which HAESL most commonly performs with its ONA EDM machines is machining the structure of the honeycomb linings that form part of some of the aircraft turbine components. The HAESL Centre of Excellence which specialises in this task was the first in the world to achieve the “Gold Award” accreditation from Rolls Royce.

Thanks to the advanced technology of the NX machine generator, the thickness of the white layer (material melted down and stuck to the surface of the workpiece) is maintained within the required tolerances even in the roughing phase. Its thickness is further reduced in the finishing phase thanks to the microfine module that is built into the generator.

In this type of work, the eroded material usually forms globules that adhere to the workpiece during the roughing process. These globules are practically eliminated during the finishing cycle (final roughness VDI 31 or lower). In order to achieve this end result without globules adhering to the workpiece, there is no need to reduce the speed of erosion or modify the standard erosion parameters of the NX machine generator.

The ONA long-life ecological filter offers a significant advantage in this process thanks to the excellent quality of filtration (1 micron) which it constantly provides. The continuous flow of perfectly clean dielectric reduces the risk of residues adhering to the workpiece and unwanted electrical discharges.

• Company: Hong Kong Aero Engine Services Limited (HAESL). HAESL is a joint venture involving Rolls-Royce PLC (45%), Hong Kong Aircraft Engineering Company Limited (HAECO) (45%), and SIA Engineering Company (SIAEC) (10%). HAESL combines the strength of Rolls-Royce as an original engine manufacturer (OEM) and the 35 years’ experience of SIAEC and HAECO in repairing and reconditioningRolls-Royceengines.

• Activity: HAESL provides repair and maintenance services for aircraft engines and components to the most respected airlines in the world which have chosen Rolls-Royce to power their fleet of Airbus and Boeing aircraft.

• Machines installed: 2 ONA machines.

• Application: Erosion of the honeycomb lining structure on the component of a low pressure turbine of an aircraft engine.

• Machine model: ONA NX7 with 100 A generator.

• Base Material: Honeycomb

• Electrode: graphite (6 microns).

• No. of electrodes used: 1

• Final roughness obtained: 31 VDI (3,50 µm Ra)

• Thickness of the white layer: <0.035 mm