Particle-based simulations and dimensional analysis of selective laser sintering of PA12 powder C. Bierwisch, S. Mohseni-Mofdi, B. Dietemann, J. Rudlof, S. Baumann, K. Popp and M. Lang II International Conference on Simulation for Additive Manufacturing - Sim-AM 2019 F. Auricchio, E. Rank, P. Steinmann, S. Kollmannsberger and S. Morganti (Eds) PARTICLE-BASED SIMULATIONS AND DIMENSIONAL ANALYSIS OF SELECTIVE LASER SINTERING OF PA12 POWDER Sim-AM 2019 CLAAS BIERWISCH * , SHOYA MOHSENI-MOFIDI * , BASTIEN DIETEMANN * , JOHANNES RUDLOFF † , STÉPHANIE BAUMANN † , KEVIN POPP † AND MARIELUISE LANG † * Fraunhofer IWM Wöhlerstr. 11, 79108 Freiburg, Germany e-mail: claas.bierwisch@iwm.fraunhofer.de, www.simpartix.com † SKZ – German Plastics Center Friedrich-Bergius-Ring 22, 97076 Würzburg, Germany e-mail: j.rudloff@skz.de, www.skz.de Key words: Melt track, grain scale, mesh free simulation, smoothed particle hydrodynamics, experimental validation, dimensionless numbers Abstract. A numerical model based on the Smoothed Particle Hydrodynamics (SPH) method is developed for 2D and 3D simulations of the laser sintering process of polyamide 12 (PA12) powder on the grain scale. Melt track simulations yield detailed insights in the visco-thermal dynamics of the process including the porosity evolution. The simulations are validated by measurements of the transient surface temperature. A dimensional analysis of the process allows for quantification of the importance of all involved physical mechanisms and predicts the magnitudes of the observable physical quantities with good accuracy. 1 INTRODUCTION Early sintering models are provided by Frenkel [1] and Mackenzie & Shuttleworth [2] describing the behavior of metal particles. In both models the material properties particle diameter, viscosity and surface tension are used to quantify differences in the sintering behavior. The model of Frenkel is later used for the rotation sintering process and modified for the inclusion of viscoelastic effects [3]. The early models are modified and used by Schultz to describe the laser sintering (LS) process of polycarbonate and polyethylene-oxide [4]. Schultz validates his models with a self-built LS machine and found a basic agreement between calculated and measured part densities. Riedlbauer et al. model the heat transfer in laser sintering of PA12 using a homogenized finite element analysis [5]. They predict the width and depth of a melt track and find good agreement with experimental measurements. Wohlgemuth & Alig study the physical modelling of the additive sintering processes for polymer materials including viscoelasticity [6]. All models taking viscoelastic effects into account incorporate a relaxation time which can be measured in a rheometer. Osmanlic et al. develop a ray tracing model for the laser beam absorption in the powder bed [7]. They find that the effective laser penetration depth in the powder can be lower than in bulk material. 316