We study the packing of fine glass powders of mean particle diameter in the range (4–52) μm both experimentally and by numerical DEM simulations. We obtain quantitative agreement between the experimental and numerical results, if both types of attractive forces of particle interaction, adhesion and non-bonded van der Waals forces are taken into account. Our results suggest that considering only viscoelastic and adhesive forces in DEM simulations may lead to incorrect numerical predictions of the behavior of fine powders. Based on the results from simulations and experiments, we propose a mathematical expression to estimate the packing fraction of fine polydisperse powders as a function of the average particle size.

Additive manufacturing processes like selective laser beam melting of polymers (LBM) are established for production of prototypes and individualized parts. The transfer to serial production currently is hindered by the limited availability of polymer powders with good processability.Within this contribution the effect of powder properties, such as particle size, shape and flowability on the processability in LBM and their influence on device quality is exemplified for polybutylene terephthalate (PBT) materials. A process chain for the production of spherical polymer microparticles has been developed to obtain PBT powder materials. The process chain consists of three steps: First, polymer microparticles are produced by wet grinding.Second, the particle shape is engineered by rounding in a heated downer reactor to improve the flowability of the product. A further improvement of flowability of the still cohesive spherical PBT particles is realized by dry coating with fumed silica.

Highlights-new process chain for producing LBM polymer powders with good flowability -wet grinding of commercially available polymer granules allows for small product size -rounding of polymer grinding product in a downer reactor -nanoparticulate surface modification by dry coating increases surface roughness -improvement of flowability of rounded polymer microparticles by dry coating

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