The absorbtion distribution as a variable property during laser beam cutting

Abstract

The laser cutting process is essentially effected by the laser beam parameters such as power, mode, polarization, focal position and beam divergence. They determine the geometry and the absorption behaviour of the cutting front and correlate strongly with the practicable cutting speed and the obtainable quality of the cut.To get a fundamental understanding of these correlations, in a first step, the distribution of the absorbed laser intensity is calculated under the presumption of a three dimensional cutting front model by applying the Fresnel formalism. The resulting theoretical influence of the above mentioned parameters on the integral and homogeneity of the absorption distribution within the cutting front co-ordinate system makes experimental results explicable and yields a new insight into the process.Calculations of the power balance, considering also an estimation of heat losses and appropriate cutting experiments on various metallic materials are in accordance with the predicted average absorptivity of the idealized cutting front.In a second step, the combination of absorption and power balance calculations leads to a self-consistent three dimensional model of laser beam cutting which delivers the parameter dependances of the stationary cutting front.The laser cutting process is essentially effected by the laser beam parameters such as power, mode, polarization, focal position and beam divergence. They determine the geometry and the absorption behaviour of the cutting front and correlate strongly with the practicable cutting speed and the obtainable quality of the cut.To get a fundamental understanding of these correlations, in a first step, the distribution of the absorbed laser intensity is calculated under the presumption of a three dimensional cutting front model by applying the Fresnel formalism. The resulting theoretical influence of the above mentioned parameters on the integral and homogeneity of the absorption distribution within the cutting front co-ordinate system makes experimental results explicable and yields a new insight into the process.Calculations of the power balance, considering also an estimation of heat losses and appropriate cutting experiments on various metallic materials are in accordance with the predicted average absorptiv...