AEROSPACE


broader, resulting in a higher speed, lower quality cut. Rofin FL fibre lasers operating at 2-3kW – technology now owned by Coherent – are used to make these faster cuts, while pulsed UV lasers are used to achieve the slower but higher-quality results. Coherent’s lasers also play a role in cleaning


carbon fibre material during production. ‘Our nanosecond and picosecond lasers are used in laser ablation processes for surface treatments, where the surface is cleaned to improve the bonding strength of carbon fibre reinforced plastic components,’ commented Kleine. Ablation can additionally improve the operating efficiencies of mechanical parts. ‘Lasers are also used to treat the side wall surfaces of piston engines,’ Kleine explained. ‘Tis process reduces friction and increases the lifetime of the piston itself.’


Layer by layer Several of Coherent’s customers build aerospace manufacturing equipment. ‘One of the biggest applications that we see in aerospace is additive manufacturing with fibre and diode lasers,’ Kleine observed. Te diversity offered by producing structures layer by layer has led to metal additive manufacturing being used for both part maintenance and the manufacturing of complete components, making it a key technique in the aerospace industry. Te additive manufacturing systems provided


MTorres supplies automated fibre placement and automated tape laying machines to produce carbon fibre wing skins


more tape. Aſter that, the material is infused with an epoxy resin similar to that of the prepreg. Te structure is then cured in an oven, rather than an autoclave, which greatly reduces the time needed for the structure to set, along with reducing the investment and operation costs. ‘Dry carbon fibre is a process that may grow in


the future,’ said Montón. ‘Tere are some customers who are starting to use dry carbon fibre materials, since they are cheaper to produce.’ At the EPIC event in Vilnius, Montón


expressed in a keynote speech that heat treating dry carbon fibre with lasers is becoming more widely adopted in the aerospace industry. Montón also hinted that modular optical systems with auto-focusing capabilities may be required to process the increasing complexity of parts that can be achieved with these new manufacturing techniques.


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Making the right cut With the increased adoption of carbon fibre materials, manufacturers will require tools that are able to process them efficiently. ‘Tere are two approaches that can be used to cut carbon fibre,’ explained Klaus Kleine, director of laser applications at Coherent. ‘If you want to melt the material at a fast pace on the front of the cutting curve you use fibre lasers in the kilowatt power range, and for high quality cutting you use a pulsed UV laser in a 305-355nm wavelength range.’ UV lasers offer strong


by Coherent’s customers use a method of powder deposition to spread a metal powder layer between 20µm and 100µm thick onto a substrate plate. Once the powder layer is distributed, a laser is used to melt and bond successive layers together. For these applications, a CW fibre laser typically in the range of 500-1,000W is used; however, a diode laser operating at similar powers is sometimes used when high beam quality is not required. Additive manufacturing is an important


carbon fibre with lasers is becoming more widely adopted in the aerospace industry


wavelength absorption with a small heat-affected zone, enabling them to produce relatively slow but high-quality cuts. Radiation from CW fibre lasers in the range of 1,070nm is also absorbed well by the material, although the heat-affected zone is


Heat treating dry


technique for repairing damaged parts. ‘It has big applications in the repair of turbine blade tips, as well as general repairs to turbine engines,’ Kleine said. ‘Te laser beam quality is not that important in this use of additive manufacturing.’ A diode laser is sufficient in this application to clad or coat material to worn sections of the turbine that have


been damaged by the 1,400°C engine temperatures, allowing them to be returned to near-pristine condition. Manufacturer of industrial laser systems OR Laser provides both direct metal deposition


ISSUE 33 • WINTER 2016 LASER SYSTEMS EUROPE 15


MTorres


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