Using lasers to cut sheet metal is something that has typically been handled in the realm of CO₂ and fiber lasers, although this may not be the case for much longer. Diode lasers are increasingly emerging as the light source of choice for a large number of applications, as can be seen from the BRILAMET research project that has just come to a successful conclusion.

There is a great deal of interest surrounding laser cutting, and events related to this topic often draw plenty of publicity. One recently-concluded research project in particular will likely attract even more attention, especially for applications in the sheet-metal industry, namely: the BRILAMET (brilliant high-power diode lasers for metal processing) joint research project, which was carried out between July 2012 and June 2015 as part of the German Federal Ministry of Education and Research program entitled “KMU-Innovativ, Optische Technologien” (“optical technologies in innovative small and medium-sized enterprises”).

During this research period, the Laser Center at the Münster University of Applied Sciences (LFM) teamed up with the Dortmund-based LIMO Lissotschenko Mikrooptik GmbH to conduct extensive experiments in the area of precision cutting for thick metal sheets.

Initially, the project involved the use of a 2.5 kW 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 fiber, the HPDL beam was then guided to the cutting head, which was also developed by LIMO.

LFM and LIMO employed the “Design of Experiments” methodology to optimize 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 4 kW HPDL beam source, which likewise consisted of two laser units coupled together.

Among other things, the project showed that although a high-power diode laser operates at a relatively modest brilliance, it is well suitable for the rapid and precise fine cutting of 6 mm thick stainless steel (speed greater than 2.0 m/min., roughness Rz less than 30 µm).

“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,” said Dr. Jens Meinschien, VP of innovations management at LIMO. “By making further laser beam-shaping adjustments, cutting speeds of 2.5 m/min can even be achieved with 4 kW diode lasers.”

But the experts at the Dortmund-based company were interested in more than just using HPDL beam sources to optimize high-precision laser cutting processes.

“Over the past three years of close cooperation with the laser specialists at the Münster University of Applied Sciences, we have acquired a great deal of additional expertise,” said Meinschien. “We now know how to improve the components and, most importantly, the beam-shaping systems for kW beam sources using an adapted optical, mechanical and thermal design.”

LIMO has presented the results of the project at international trade fairs and conferences as well as in trade journals, and the findings have caught the attention of experts throughout the field. The entire topic appears to be somewhat of a never-ending story for LIMO, as the Dortmund-based company is currently pursuing additional laser-cutting research alongside internationally renowned experts as part of the EU “Lashare/Nextcut“ sub-project.

“I am eager to see what kind of additional expertise we can gain from this research collaboration,” said Meinschien.

LIMO Lissotschenko Mikrooptik GmbH
www.limo.de/en/

Laser Center at the Münster University of Applied Sciences
www.muenster.de