A wealth of laser joining techniques, including those being developed as part of various European projects, were discussed at a TWI event on laser welding, which took place on 19 July just outside Cambridge, UK.
Delegates from motoring companies including Nissan, Jaguar Land Rover, Hyundai, and Fiat – as well as those from the energy, aerospace and metalworking sectors – attended the day hosted by the materials joining institute to hear talks on topics ranging from micro-joining of electronics to thick-section structural applications in the energy industry.
TWI has a rich heritage of working with laser technology. In the opening presentation recounting some of the highlights of laser material processing at TWI over the last 50 years, Paul Hilton, a technology fellow at TWI, showed the two pieces of metal from the world’s first ever laser cut. The experiments were the idea of Peter Houldcroft, the then deputy scientific director of TWI. He and his colleague, ABJ Sullivan, cut the 1mm thick steel sheet with an oxygen assisted CO2 laser beam in May 1967 at the Services Electronic Research Laboratory in Harlow, just down the road from TWI .
Today, TWI is involved in various UK and European R&D projects, including a number in the UK nuclear energy sector – laser technology developed by TWI is currently being used for decommissioning at both Hinkley Point A nuclear power station in Somerset and Sellafield in Cumbria.
Tony Pramanik, a project leader at TWI, spoke about the various laser welding projects for the nuclear industry, starting with LaserPipe, a collaborative project with OC Robotics that ran from January 2015 to December 2015. The result of the work was a snake-arm robot containing a high-power laser that could be used for in-bore pipe welding in nuclear power stations. The team managed to weld pipe sections that were only accessible through pressure vessels or manifolds and maintenance ports.
Pramanik also discussed TailorWeld, a three-year project that began at the end of 2013. The aim is to develop suitable tailored energy distributions for laser welding applications, reducing the high initial capital investment required for laser welding systems. Diffractive optical elements are being produced by HoloOr to tailor the beam profile.
ModuLase was the final project mentioned by Pramanik. It is a three-year Horizon 2020-funded study due to start in September 2016, and looks to build a rapidly re-configurable laser processing head able to weld, clad and cut.
Outside of the nuclear energy sector, TWI is active in the Merlin project that aims to reduce the environmental impact of air transport using additive manufacturing. TWI is working on some of the non-destructive testing (NDT) equipment necessary to ensure the structural integrity of the additive parts.
Ian Cooper, a technology fellow at TWI, explained that the NDT equipment for Merlin uses sound waves to probe the part for flaws. Acoustic waves reverberating across a material’s surface will alter in the presence of defects, which can be picked up by a laser interferometer.
Dr Choon Yen Kong gave an overview of the LASHARE project, standing for ‘Laser equipment assessment for high impact innovation in the manufacturing European industry’. The project involves more than 30 SMEs from across Europe, along with industry partners and six laser research institutes.
There are 24 mini projects within LASHARE – laser-based equipment assessments that are designed to determine the requirements and needs of users when selecting laser equipment. The projects assist suppliers on assessing their technology readiness levels (TRLs). New laser-based equipment is also assessed on its impact on manufacturing and business processes as a part of the LASHARE project. The up- and down-stream implications of the equipment are analysed to ensure that a reduction of the technical and commercial risks is achieved.
Laser welding in the automotive sector was also covered during the day. Sullivan Smith spoke about laser joining lightweight materials such as aluminium, which is now used more frequently in car production. He also explained the benefits of pre-weld processes such as cold spray surface preparation, which can result in improved weld quality.
Ali Khan of TWI discussed micro joining in energy storage devices, which will be key to produce the next generation of batteries for electric vehicles. One of the challenges of using a laser to join copper connectors is that copper reflects around 97 per cent of infrared radiation at room temperature. Khan explained that green laser light is preferable for this process, but that higher power lasers are needed to make the welds effectively.
There were also presentations on TWI’s Clearweld process for transmission laser welding of plastics, joining thick materials (up to tens of millimetres) with hybrid laser arc welding, and analysing plasma plumes for quality assurance. In the final talk of the day, Darren Williams spoke about Industry 4.0, the current trend of automation and data exchange in manufacturing, in which TWI is beginning to get involved.
1. ABJ Sullivan and PT Houldcroft: 'Gas-jet laser cutting', British Welding Journal, August 1967, pp.443.