Dortmund, Germany - The term “high brightness,” which combines high optical power with good beam quality, has so far only been marginally related to high power diode lasers (HPDL). Therefore, the cutting of several millimeter-thick steel sheets with good quality and reasonable cutting speed by means of HPDL had not been achievable so far.
With recent progress on HPDL modules and their optical interconnection using special micro-optics, a 2.5 kW laser with high power and high brightness has now been demonstrated by LIMO Lissotschenko Mikrooptik GmbH.
The specialists for laser beam shaping have studied the potential for applications in materials processing together with the Laser Centre at the University of Applied Sciences Münster (LFM). For this purpose, the light of a 2.5 kW laser was fed by an optical fiber (core diameter = 400 microns) to a newly designed processing head from LIMO (focal length 120 mm). The metal processing was performed on an industrial CNC machining facility (see Fig. 1 above). The cutting process was optimized using the methodology of “Design of Experiments,” including variation of nozzle geometries and diameters.
LIMO and the LFM cooperate within the joint project BRILAMET (brilliant high power diode lasers for metal processing) which is funded by the German Federal Ministry of Education and Research (BMBF). This project is supported by the BMBF program "KMU-Innovativ, Optische Technologien" (Optical Technologies in innovative small and medium-sized enterprises, promotional reference: 13N12282). As a result of a successful milestone, laser cutting of steel was demonstrated: 6 mm thick stainless steel (1.4301) was cut at 1.1 m/min and 6 mm thick mild steel (1.0038) at 2 m/min. In both cases, a very good cutting quality was achieved with a roughness Rz < 35 microns and negligible dross on the kerf (< 30 microns) (Fig. 2 below).
As the project continues, these investigations will be continuously extended. LIMO is going to increase the optical output power of the laser up to 4 kW while keeping the brightness on a high level.
Fig. 1: (top) 2.5 kW high power diode laser from LIMO (upright in the center) coupled with an industrial CNC machining facility (left) for metal cutting at the Laser Centre of the University of Applied Sciences Münster (LFM). Courtesy: LFM
Fig. 2: (bottom) Metal sheets of 6 mm thickness were cut at high speed by means of a 2.5 kW high power diode laser (LIMO). Left: stainless steel (1.1 m/min.); right: mild steel (2.0 m/min.) Courtesy: LFM