Cut edge structures and gas boundary layer characteristics in laser beam fusion cutting

Fiber laser fusion cutting trials on AISI 304 stainless steel sheets of 10 mm thickness were performed to gain further insight into the formation mechanisms of topographical features of cut edges. It is found that particularly the variation of focus position causes distinct processing regimes with completely different cut edge structures. Standard cut edges can be divided in six different structural zones. It has become obvious that particular details of the different cut edge zones can be only understood as a result of a rather complex cutting gas flow. Corresponding high-resolution CFD simulations of the cutting gas elucidate the structure of the supersonic flow field and particular boundary layer characteristics. The results strongly support the hypothesis that the cutting gas flow and particularly the stability of the gas boundary layer plays an important role for the generation of the final cut edge topography.