Selective laser melting of polymers: Influence of powder coating on mechanical part properties

For the derivation of part quality increasing process strategies, knowledge about interactions between sub-processes of selective laser melting (SLM) and resulting part properties is necessary. The SLM process consists of three major sub-processes: powder coating, exposure, and material consolidation. According to the interaction of sub-processes, resulting processing conditions during SLM determine the part properties by changing micro structural pore number and distribution. In addition to absolute temperatures, the time-dependency of the thermal fields also influences the porosity of molten parts. Present process strategies tend to decrease building time by acceleration of the subprocesses. Apart from prior investigated acceleration of the exposure, the powder coating step is focused. Within the paper, the authors analyze the basic interactions between different coating parameters and part properties. The authors estimate an interaction between coating speed and resulting part properties due to a force impact caused by the moved coating mechanism. Therefore, specimens produced with different coating speeds are analyzed with imaging technologies as well as mechanical tests. Based on the investigations, new processing strategies can be established considering the forces applied to the powder bed during the coating process, as well as the unique compaction behavior of current and future used powders.