ISSUE 114 AUTUMN 2024 OBSERVATIONS


LOW-PRESSURE LASER CUTTING TO MANAGE HAZARDOUS LASER FUME JACOB LAVIN ET AL*


Sometimes it is a good idea not to go mainstream. Punk instead of Pop.


In their project, Jacob Lavin and co-authors go for "Bad Laser Cutting“. They utilise cutting gas at low pressure instead of high pressure and thus make ugly instead of brilliant cuts. Much of the molten kerf material resolidifies at the underside of the cuts as dross. This reduces the emission of particles which is an important factor in nuclear decommissioning.


Jacob and his band - to continue the metaphor of punk music - play the whole repertoire of laser cutting science in a concert of Schlieren imaging at idealised cut geometries, high-speed videography of the melt ejection, theoretical modelling and practical cutting experiments. Amongst others, they detect small, high-velocity particles being captured by large dross balls.


So far, the work comprises thin sheets (1.5 and 3 mm stainless steel) with low fibre laser beam powers (210 and 580 W), as can be read from the quoted records released by the band in the years 2022 and 2023. I suppose in future, thicker materials and higher powers as well as subsonic gas jets at even lower gas pressures will bring further hits.


Dirk Petring, Fraunhofer ILT


become more common. However, joining of these dissimilar materials using fusion based welding processes, such as laser welding, can be challenging due the low vaporisation temperature of Zn causing instability and porosity, and the formation of brittle Fe-Al intermetallic compounds.


There are various approaches to address these challenges, including the use of different modes of laser welding, beam shaping, beam oscillation, addition of a suitable filler wire, and double pass welding for example. The authors show the application of beam oscillation on Zn coated steel to aluminium dissimilar joints where some promising results were achieved, especially on weld joints where the Zn coating was removed.


It is good to see further development within this field which will lead to improvements in the current manufacturing processes available and enable a wider adoption of laser welding technology.


Junny Lai, Cranfield University


THE LASER USER


both laser absorptivity and alloy metallurgical properties. The laser-material interactions arising from these composite powders require further investigation to better understand and optimise the process.


Metallurgical benefits of these composites have been substantiated, including notable improvements in material strength and reduction in anisotropy. These enhancements underscore the potential of using metal matrix composites to address longstanding challenges in additive manufacturing.


The authors’ development of AMALLOY exemplifies a forward-looking focus in alloy optimisation without gas atomisation, but it will be useful to understand any scaling-up issues. The research demonstrates a foundation for future work in this area, and the contributions of the Technology Innovation Institute (TII) are anticipated to drive further advancements in the understanding and enhancement of LPBF feedstock formulations.


Moataz Attallah, University of Birmingham


HIGH-POWER LASER WELDING: A COMPARATIVE STUDY OF Cu & Al


RAGAVENDRAN MEENAKSHISUNDARAM


Copper and aluminium welding remains one of the most challenging applications in laser welding. The images reveal that good welds are possible with the set up. It would have been helpful to mention the contribution of the Inline process monitoring, featured in the images. In practice, in process monitoring is critical to detect gap or over-penetration of welds. From a commercial perspective the power required seems excessive, with laser powers under 1.5 kW normally being sufficient.


Mark Thompson, Photonics Express


NOVEL ALUMINIUM MATRIX COMPOSITES FOR AM APPLICATIONS


REMOTE LASER WELDING OF STEEL TO Al: DOES Zn COATING PLAY A ROLE?


ALI BAGHBANI BARENJI ET AL.*


Within the automotive industry, the use of zinc-coated steel and aluminium materials has


26 GIUSEPPE DEL GUERCIO ET AL*


The blending of nanoparticles and powder mixtures within laser powder bed fusion (LPBF) feedstocks to form metal matrix composites has been shown to influence


Ali has demonstrated improvements in weld quality of remote laser welded zinc coated steel to aluminium. Remote laser welding is used in the automotive sector due its process speed and low heat input. Additionally, demand for reducing weight in vehicles is growing, especially for electric vehicles. As such, remote laser welding of these materials presents opportunities to achieve lightweighting and production rate goals.


Laser welding of lap configured zinc coated steel is challenging, this is due to the low melting point of zinc which produces melt pool instability and zinc forms brittle intermetallic compounds at the material interface.


The results in this paper clearly show an improvement in weld quality by laser ablating the zinc coating prior to laser welding. Further work of interest would be to understand the amount of zinc that is remaining (if any) after laser ablation as well as the repeatability of the ablation and welding process.


Ryan Cotterill, MTC


MINIATURE OPTICAL DELIVERY HEADS FOR RESTRICTED ACCESS AREAS


MIKE O’KEY


The ability to “fit a quart into a pint pot” is illustrated in this excellent article. I had a little experience in the 1990’s about the design of custom focus heads for welding, and I also recall the innovative heads made for internal pipe welding by the RACE team at UKAEA. This takes miniaturisation to a higher level (albeit at lower power), and the ability to use MEMS support structures for micro-mirrors is a level of innovation that solves many technical problems of how to move the mirror to steer the beam without galvo scanning or mini- motors.


I hope that this will herald more welding and cutting heads (as well as the ablation process) to access areas that were previously unavailable. And of course the management of heat and delivery of process gas can present further challenges. Finally, this technology was presented at our Laser Cleaning workshop last year and it widened my thought process of the type of work OpTek are capable of delivering.


Dave MacLellan, AILU


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