Transition from Stable Laser Fusion Cutting Conditions to Incomplete Cutting Analysed with High-speed X-ray Imaging

摘要

The transition from stable laser cutting conditions to an incomplete cut, which is generally referred to as loss of cut, limits the maximum feed rate of laser beam cutting. In order to investigate this phenomenon, the geometry of the laser cutting front was observed by means of online high-speed X-ray diagnostics. Fusion cutting of 10 mm thick samples of aluminum and stainless steel were recorded with a framerate of 1000 Hz. A quasi threedimensional geometry of the cutting front and the kerf was reconstructed from the grey scale values of the recorded X-ray images. Comparing cutting of stainless steel and aluminum at stable conditions with the same cutting parameters, it was found that the local angle of incidence in the lower part of the cutting front is smaller and the cutting kerf is wider for stainless steel. During loss of cut, the angle of incidence on the cutting front decreased for both materials and the width of the cutting kerf in the lowest third significantly increased. The reconstructed three-dimensional geometries enable for the first time the determination of the transient changes of the local absorptivity during the loss of cut during laser beam fusion cutting.