Abstract

An analytical model that predicts the resulting surface texture (i.e., Ra roughness) of indirect-SLS metal parts after being laser surface polished has been developed. It is based on the assumption that the surface of an SIS part consists of a closed packed arrangement of hemispherical caps having a uniform diameter equal to the diameter of the precursor powder. The polishing mechanism modeled is shallow surface melting, in which a fast moving laser beam provides just enough heat energy to cause melting of surfaces. Molten mass flows from spherical apexes into the valleys driven by the pronounced difference in radius of curvature of the local liquid surface. Balance of capillary and viscous drag pressures acting on a liquid surface determines the spreading time. Subsequently, after spreading is complete, resolidified liquid filling the valleys diminishes the surface roughness. The model can predict the trend of the Ra values as a function of laser power, scan speed and average precursor powder particle size as verified by empirical data previously reported.