Laser Milling Simulation System for Moulds Manufacturing

This paper refers to the development of a numerical simulator for Laser Milling process useful for industrial applications able to predict the machining results when different materials are processed, different surface conditions are encountered and spatial and temporal distributions of the pulsed beam are set. The original software presented, developed by the authors, are well suited for simulating laser milling or laser micromachining operations with power density up to 1014 W/m2 and pulse duration in the order of nanoseconds. The temperature of the solid phase is evaluated by solving the Fourier equation by using the finite difference method (FDM). The recession velocity of the ablating surface is evaluated according to the Hertz-Knudsen equation assuming that the explosive effects are negligible. The plasma plume is considered in local thermodynamical equilibrium (LTE) and the energy balance permits to evaluate the plume temperature, ion distribution and pressure under the assumption that the gas expansion, from the surface target, produces a sonic front. The plume energy balance is influenced by the energy lost for irradiation from the plume and by the quantity of laser beam energy reflected from the target surface. Numerical simulations have been conducted to quantify this influence on the plasma plume physical state and, consequently, on the ablation process considering a Nd:YAG diode pumped source and three different target materials: Fe-C alloy, copper and aluminum.