Many of the components within the modern jet engine rely on arrays of shaped holes through which air is forced to prevent the temperature from rising to a level where the component would be damaged by excessive heating. Typical alloys are chosen for their strength, low density and weldability.
Cooling holes can be laser drilled at extreme angles to achieve the correct flow properties. The holes required can be drilled by one of two methods:
• Percussion drilling – where the laser beam is stationary and a number of pulses are fired at the component until the beam drills through completely. The shape of the hole is determined by the shape of the laser beam.
• Trepanning – where the laser beam pierces the material and then the nozzle is moved in a particular geometry to achieve a hole suited to the application. Often the hole is fan-shaped on the entry or it may be conical. The movement of the beam determines the hole geometry.
Holes are drilled in blades and nozzle guide vanes as well as in cowlings and shrouds around jet engines.
The joining of metallic alloys, chosen for their light weight, comparative strength and high melting point is an application where laser welding gives excellent results. Inconel, Titanium and aluminium alloys, are used to provide maximum strength and can be joined without adding weight to the assembly. The quality demands are rigorous and no imperfections must be apparent in the weld zone.
Traceability is most important in the aerospace market and marks need to be fast, minute in dimensions and with a combination of low heat input and permanent wear resistance. Laser marking allows a 2D matrix code to be marked on every key component, providing a machine-readable code which can hold a large amount of information in a small area.
The main advantages of a laser marked 2D matrix code are that the dimensions can be minimised and the code has an inherent large degree of redundancy meaning that it can still be read successfully even when a significant part of the code is missing or damaged.