Areal characterization of medium and high thickness laser cut edge surfaces

CO2 laser is a traditional laser source in laser cutting industries but fiber laser has become more desirable for cutting applications due to high energy efficiency, low maintenance cost, small source dimension and better absorption in metallic material. On the other hand fiber laser usually shows lower quality in high thickness. The comparison of these two laser sources is one of the most interesting challenges in industrial field. This work has tried to compare fiber laser cut with CO2 laser cut of medium and high thicknesses mild steel and stainless steel by means of new areal approach. First the standard method (ISO9013) was used to measure perpendicularity and roughness as quality assessment parameters. But the standard method for quality classification was not able to show the differences between different cuts even through the differences were recognizable by eye. Since the topography of laser cut edge surface varies in thickness and cutting directions, the standard suggested part of the surface was not able to represent all the properties of surface. This study has tried to use areal method by means of focus variation scanning microscope for having comprehensive view of total cut edge surface with high resolution. One the most important steps was selecting cutoff length for analyzing the cut edge with different parameters. For having better idea about the effect of cut-off length on the values of surface roughness parameters, a sensitivity analysis was performed and the best cutoff length window in both thickness and cutting directions was selected in order to represent the defects of the cut edge surface present in different thicknesses. Finally some areal parameters were applied to characterize the cut surface in the two selected materials and using a combination of these different parameters like height, hybrid and bearing it was possible to explain surface topography in case of comparison between two different laser sources with more details with respect to standard method.