Influence of the laser cutting front geometry on the striation formation analysed with high-speed synchrotron X-ray imaging

The generation of low surface roughness of the cut edge during laser beam cutting is a challenge. The striation pattern, which determines the surface roughness, can be distinguished into regular and interrupted striations, the latter resulting in an increased surface roughness. In order to analyse their formation, the space- and time-resolved cutting front geometry and melt film thickness were captured during laser beam fusion cutting of aluminium sheets with a framerate of 1000 Hz by means of high-speed synchrotron X-ray imaging. The comparison of the contours of the cutting fronts for a cut result with regular and interrupted striations shows that the contour fluctuates significantly more in case of interrupted striations. This leads to a strong fluctuation of the local angle of incidence. In addition, the average angle of incidence decreases, which results in an increase of the average absorbed irradiance. Both phenomena, local increase of absorbed irradiance and its dynamic fluctuation, result in a local increase of the melt film thickness at the cutting front which is responsible for the formation of the interrupted striations.

Automated summary

In laser fusion cutting of aluminum sheets, the occurrence of interrupted striations on the cut edge leads to higher surface roughness compared to regular striations. This is due to fluctuations in the local angle of incidence and the increase in average absorbed irradiance, resulting in a thicker melt film at the cutting front which is responsible for the formation of interrupted striations.