Influence of laser beam oscillation on the cutting front geometry investigated by high-speed 3D-measurements

3D measurements of the cutting fronts during laser fusion cutting were performed with and without beam oscillation. The used 3D measurement equipment offers up to 75.000 frames per second and a local resolution less 50 µm. This allows high-speed recording of dynamic changes at the cutting front geometry, followed by a three-dimensional reconstruction. Out of an extensive study was picked out a parameter set for 8 kW laser power and a feed rate of 4.5 m/min cutting 10 mm stainless steel (AISI 304), compared to a cut with additional longitudinal beam oscillation by a frequency of 600 Hz and an amplitude of 0.15 mm. The large bright spots of common high speed videos can be interpreted as melt accumulations, pushed down by the gas pressure. They leave behind cold spots on the cutting front, which are very steep or even have an undercut. The influence of beam oscillation on the cutting front is also clearly visible. In the places where the laser beam is not currently located, the melt and the resulting structures appear to solidify. As a result, melt is not continuously ejected, but rather melt bursts are created with the oscillation frequency.