In the past additive manufacturing processes such as laser beam melting (LBM) were almost exclusively applied for the generation of prototypes. In recent years, however, these methods have gradually been transferred to serial production (1). With this grown relevance on industrial applications, the demands on the powder material have increased as well. In consequence, there is a need for fine powders of different polymers showing good powder flowability and high bulk density (2) It has been shown that different polymers can be ground down to the micron size range by a wet grinding process (2). Due to the grinding process the produced particles are in a chiseled state, which leads to a bad flowability. To solve this problem the single particles are melted in a heated downer reactor and spherical particles are obtained by using the effect of the surface tension (3). The rounding process was performed in a reactor with a length of 6 m and a diameter of 0.1 m. The main focus of this work is to describe the flow characteristics of both, gas and particles in the reactor. Other influencing parameters on the outcome of the rounding such as particle load and temperature distribution will also be addressed. One major critical point, the influence of the particle and gas inlet on the flow pattern will be discussed in detail. The mechanism of the rounding process in dependence of particle size, interfacial tension and melt viscosity will be shown within a sintering model (4).
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