Surface Roughness Enhancement of Indirect-SLS Metal Parts by Laser Surface Polishing

Abstract

Laser polishing by means of shallow surface melting of indirect-SLS metal parts was achieved using high power CO2 and Nd:YAG lasers raster scanned at high speed. This was an effective technique for reducing surface roughness. The fast moving laser beam provides just enough heat energy to cause melting of the surface peaks. The molten mass then flows into the surface valleys by surface tension, gravity and laser pressure, thus diminishing the roughness. Surface roughness Ra data were obtained by profilometry measurements of the polished samples. An analytical model was developed based on the assumption that the surface of an SLS part consists of semi-spherical caps. The model was used to predict the Ra values as a function of laser power, scan speed and precursor powder particle size. The modeled results fit the empirical data within a 15% error.