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Diode laser project achieves 6mm steel cutting

A direct diode laser system capable of cutting 6mm thick stainless steel at speeds of 2.0m/min has been developed as part of a three-year research project. The BRILAMET (brilliant high-power diode lasers for metal processing) joint research programme used 2.5kW and 4kW high-power diode laser sources to cut the sheet metal, achieving a roughness of less than 30µm.

The project, which ended in June, was a joint initiative between the Laser Center at the Münster University of Applied Sciences (LFM) and Dortmund-based LIMO Lissotschenko Mikrooptik.

Using lasers to cut sheet metal is something that has typically been the realm of CO2 and fibre lasers, as the beam quality of diode lasers has traditionally not been good enough to produce a high quality cut. However, there are now commercial kilowatt direct diode systems available targeted at cutting sheet metal, such as those from JDSU.

The BRILAMET project gained insights into the beam-shaping systems for kilowatt beam sources using an adapted optical, mechanical and thermal design, according to Dr Jens Meinschien, vice president innovations management at LIMO.

‘The key ingredient here is not only the asymmetrical laser beam geometry but also the model for predicting machining results, which was developed during the project,’ added Meinschien. ‘By making further laser beam-shaping adjustments, cutting speeds of 2.5m/min can even be achieved with 4kW diode lasers.’

Initially, the project involved the use of a 2.5kW high-power diode laser (HPDL) that was coupled to industrial CNC machining equipment. LIMO had used special micro-optics to optically connect the HPDL beam source modules. Through an optical fibre, the HPDL beam was then guided to the cutting head, which was also developed by LIMO.

LFM and LIMO employed the Design of Experiments (DOE) methodology to optimise the cutting process by experimenting with different nozzle geometries and diameters, as well as with other aspects. As the project progressed, the experiments were expanded to include a 4kW HPDL beam source, which likewise consisted of two laser units coupled together.

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