Determination of the lower complexity limit for laser cut quality modelling

In this paper the authors address the modelling of surface profiles resulting from the laser cutting process. Despite the attention paid to this problem by the scientific community, the phenomena of striation formation is still only marginally understood. The models used in the literature are often highly simplified and focused on single large scale effects such as exothermic reactions of the melt with the assist gas. In this work a three-dimensional fully coupled model for the laser cutting process is used. It will be shown by the authors that, if details of the cut face surface profile, dross and burnout are sought, simplifications like reduction in model dimension and the neglect of gas dynamics, viscous shear, convection effects and melt flow dynamics are not admissible, and that those 'small' effects induce identifiable differences within the cut surface profile. However, it has also been found by the authors that currently available computer hardware is not capable of producing results at the necessary rate and cost required for parametric studies. Results from nine simulation runs amounting to 17 300 cpu hours on a SGI origin 3400 system are presented. These are intended to be taken as cautionary examples with regard to the numerical models applied and thus establish a lower limit of modelling complexity. This lower limit can then be built upon by introducing exothermic reaction, plasma formation, multiple reflections and the like.