Comparative analysis of the potential of state-of-the-art lasers and new prototypic high-power beam sources for cutting nonmetals

At Fraunhofer IWS Dresden, different, partially prototypic high-power continuous wave (cw) beam sources for the remote laser processing of nonmetals with galvanometric-driven scanner systems are available. The emitted wavelengths of the lasers cover the range from visible light to mid-infrared. A spectroscopic analysis was performed to gain insight into the processability of typical nonmetal materials with single wavelengths. The wavelength-depending absorption was calculated based on the measured reflectivity and transmissivity of the selected materials. Relating to these results, the theoretic potential of the beam sources was verified in a comparable cutting research. The investigated work pieces are representatives of the groups of thermoplastics and thermosets, fiber-reinforced polymers, glasses, natural fiber textiles, and cellulosic based materials. The laser systems were divided in two groups for the investigation. To get a reference of the processability with state-of-the-art cw systems, a CO2 laser with a wavelength of 10.6 mu m and a solid-state Yb:YAG fiber laser with 1.07 mu m were used. The new prototypic beam sources were a green laser with a wavelength of 0.515 mu m, a CO laser with a range of 5.3-5.8 mu m, and a CO2 laser with 9.3 mu m in a power range from 1 to 1.5 kW. Differences in the possible focusability are caused by the wavelengths and given beam qualities. For a direct comparison, these differences needed to be compensated. To get comparable intensities, the spot diameter in the working distance for each laser was set to 250 mu m. This allows to process the materials with almost the same intensities. Since the laser sources with the short wavelengths offer a better focusability, experiments with the smallest possible focus diameters for the used optics were performed to get an optimized ablation result. Finally, the aim of the research was to evaluate the suitability of the available beam sources for new fields of application. The latest results of experimental and theoretical investigations on the remote laser processing of nonmetals with a wide range of laser wavelength will be presented and discussed.