Process parameters for high quality on-contour starting of laser cutting of steel

Laser cut initiation in full material usually results in a start hole with bad quality. Starting strategies have been developed to avoid these crater-like holes. Start areas were obtained showing almost the same quality as the rest of the cut. As a result of the experiments and literature research the following starting strategy has been applied: drilling in a pulsed laser mode followed by a power ramp in c.w. laser mode simultaneous with the acceleration of the workpiece. The chosen strategy has been implemented in the laser controller. For mild and stainless steel of various thicknesses start settings have been determined. The best results were found at relatively low acceleration (1 m/s2). The power ramp during acceleration has been proven to be more advantageous for thin (1 mm) mild and stainless steel than for thickness sheets. A slightly varying kerf width over the first millimeters of the cut has been observed. This can be explained by varying cutting front velocity and temperature caused by the workpiece acceleration.