Optimisation of laser cutting process in relation to the maximum cutting speeds using numerical modelling

Full text: Laser cutting of steel is nowadays a well established industrial process. Manufacturers using laser cutting in their production are particularly interested in attainment of high cutting speeds for maximization of productivity and cutting reproducibility by Optimization of the processing parameters. In the present study, the maximum cutting speed is investigated as a function of laser power and gas jet velocity. For this purpose, a three-dimensional transient finite volume model has been constructed, based on the Navier–Stokes equations and energy conservation equation for the description of momentum and heat transport phenomena, and the Volume of Fluid (VOF) method for free surface tracking. The Fresnel absorption model is used to handle the absorption of the incident wave by the surface of the liquid metal and the enthalpy-porosity technique is employed to account for the latent heat during melting and solidification of the material. The main objective of using a transient phase change model in the current case is to simulate the dynamics and geometry of a growing laser-cutting generated kerf until it becomes fully developed. It was observed that when the cutting speed is increased high enough for a given laser power level, a maximum cutting speed is reached beyond which the laser power is insufficient to produce complete cutting. The maximum cutting speed is defined as the speed for which the calculated cutting profile is just deep enough to cut through a workpiece of a given thickness. The results show that maximum cutting speed increases by rising the laser power and assist gas velocity. The results indicate an intense influence of the laser power on the maximum cutting speed. (author)