Rough-cut fast numerical investigation of temperature fields in selective laser sintering/melting

Abstract

This paper investigates selective laser sintering/melting (SLS/SLM) processes by a thermal model solved with a finite difference scheme. The density equation is semi-empirical based on the Arrhenius equation and experimental results taken from literature. Energy distribution function in the laser beam is appropriately considered. The main input parameters studied were as follows: laser speed, preheating temperature and laser power. The output parameters were maximum temperature and consolidation area. SLS was tried on polycarbonate powder and SLM on a Ni superalloy. Variations of temperature and density with time at the centre of the beam and at another two points at increasing distances from it were found to be qualitatively similar irrespective of the laser speed and power. Maximum temperature reached is not affected significantly by preheating temperature, by contrast to the consolidated depth and consolidation area. The latter are also affected by laser power. Increase in laser speed leads, as expected, to a decrease in consolidation depth and area as well as a decrease in maximum temperature. Continuous and pulsed lasers exhibited large differences; e.g. for the same speed and power, a pulsed laser results in much lower temperature gradients during cooling. The model can be used to obtain a preliminary picture of the response of any material to SLS/SLM processing provided that the appropriate input data is available, which is a crucial factor not to be underestimated.