In the aerospace industry, the multiple processing applications have been accepted about 30 years back with the pulsed Nd-YAG laser and still in use in production. However, with the use of the fibre laser technology and the evolution & development of the reliable fibre laser source, the applications in the aerospace industry have got substantial acceptance in aerospace industries. Fibre lasers have taken a huge share of Nd-YAG lasers as they do not require warm-up and maintenance. The aerospace industry is benefitting greatly for conversion to fibre laser technology.
The requirements in aerospace
The modern requirements in aerospace has millions of holes in turbine engine. They can be of different shapes, angles and diameters. Moreover, the aerospace industry has been constantly looking for new techniques to save fuel and consumption. It has been a challenge to reduce cost at all levels. Focus has always been to improve strength and reduce density to achieve these goals. Other strategies have been to find new fabrication techniques and processes that reduce the manufacturing costs. The components of aerospace are low in volume, but requirements are precise and labour-intense. This challenge has been well served by laser material processing for thirty years. The aerospace has been the industry where SIL has put efforts to support through the applications of fabrication cutting, welding and precision drilling.
The cost of laser equipment maintenance and old technology has been a challenge to cope with the requirements. Lasers have been the rapid processing single-step tool and adaptive to the process. At present, traditional laser systems such as, continuous wave (CW) and nano-second pulsed lasers dominate the aeronautic fabrications. CO2 laser operates at continuous mode with a wavelength of 10.6 μm. This type of laser is the earliest used in aerospace manufacturing. Nd-YAG lasers are primarily of the pulsed type. The wavelength is in the near infrared at 1.06 μm.
Fibre lasers have gained interest over the years and taken up a major share of old traditional laser systems. Fibre Ytterbium lasers operate at a wavelength of 1.07 μm. Fibre lasers in power of few hundred to thousands are used for cutting application, fusion welding of alloy and super alloy sheets. Pulsed fibre lasers with very high peak power and average power in hundreds of watts are used for drilling in turbine engine. These drillings are deep drillings in the number of millions of different diameters and angles. Fibre laser technology has made this possible due to the stable focus and diameter of the laser beam constant. The short focus can be made so as to carry percussion welding and trepanning operations using CNC. Die moulding machines have made it a possibility to repair the blades of gas turbines in aircraft engines. Robotic welding applications have been a boon to critical components welding.
Laser as a tool
Another advantage of using lasers as a tool is that the laser material processing is highly versatile. By tuning laser parameters, multiple tasks such as, cutting, drilling, welding and cladding and marking critical components — all can be carried out with a single machine. Laser source, being a tool in general, is required to sharpen the tool by parametric and optical selection of optics and make it suitable for the required operations of the industry at best.
Traditionally, CW lasers and pulsed lasers were used for cutting and drilling work on the thermal heating mechanism, where the material is melted and evaporated upon absorbing laser photon energy. This process occurs very fast, usually in the time scale of a nano-second to a micro-second. Therefore, laser systems are capable of processing materials at a very high rate.
However, the major challenge in material processing has been burrs in cutting or drilling operations. The molten material may require secondary operation and that makes the laser application use challenging.
However, ultrafast lasers such as, the pico-second laser or the femto-second laser, used for drilling and precision cutting application in aerospace, have taken care of heat zone issues and reductions in burr. These ultrafast lasers have extreme short pulses, the peak power reaches giga watts so almost all kinds of materials can be processed with direct fragmentation rather than heat mechanism. The process minimises the heat zone and burr in production. Emerging ultrafast laser material processing in aeronautics industry is driven by these two factors.
As of now, micro-machining applications are done by ultrafast lasers. Advancement of laser technology in ultrafast laser has given opportunity for macro-scale material processing for the aerospace industry where the drilling of precision diameters and millions of holes are required in turbine engine at different angles.
SIL has developed applications in the field of drilling, cutting and welding of different alloys with lasers. Selection of optics and laser source from femto-second to CW lasers and processing laser has given an edge in the market for different industrial applications from macro to micro machining applications. The company has developed 6-metre laser tube cutting applications that can be processed to full length without any waste of material in profile cut. It has a single platform application for cut and weld of 2D metal sheets.
Non-metallic applications of welding and cutting have also been developed to support the interiors of the aerospace industry.