Investigation of the Influence of the Mixing Process on the Powder Characteristics for Cyclic Reuse in Selective Laser Sintering

Abstract

Selective laser sintering (SLS) with polymers is currently at the transition to the production of functional components and thus holds great potential to revolutionize conventional production processes. Nevertheless, the application capability is confronted by newly defined requirements regarding reliability and reproducibility. In order to fulfil the requirements and to increase the process stability, the ageing mechanisms in polymers are compensated by recycling strategies. This involves fraction-based mixing of a defined ratio of new powder with recycled powder. Basically, fraction-based mixing must be preceded by the selection of suitable mixing parameters. The work focused on the influence of the mixing process on the powder characteristics for cyclic reuse in SLS. With regard to the powder characteristics, the particle shape and particle size distribution as well as the bulk and tap density of the powder were investigated. The authors found an influence of the mixing process with increasing mixing time on the powder characteristics of a black polyamide 12 sintering material. A mixing time of 1 h and a mixing intensity of 15 rpm proved to be potentially effective for achieving a gentle and homogeneous mixing of the powders.