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Regarding raw materials characterization, few relevant measurement methods are available in the market to answer the needs of Additive Manufacturing (AM). Indeed, the stress state (ambient and/or thermal) and the flow field of the powder should be comparable in the measurement cell and in the process. With this information in mind, GranuTools has developed a workflow for powder characterization. Our main goal is to have one instrument per geometry that mimics the process. In the present paper, we have shown how this range of instruments can be used to follow the quality evolution of a powder after several printing processes. First, the standard aluminum alloys are selected and placed under different thermal stresses. The powders spreadability (GranuDrum Instrument), the packing dynamics (GranuPack Instrument) and the electrostatic behavior (GranuCharge Instrument) were then analyzed. This analysis is showing that it is possible to monitor thermal degradation by analyzing the ability of the powder to build-up electrical charge. Indeed, on one hand, a low Cohesive Index is observed for a powder easy to spread and a fast packing dynamic yield a mechanical piece with a lower porosity. However, on the other hand, the powders with high cohesive index at ambient temperature are showing better spreadability and high compaction after thermal degradation, which is highly desirable for the AM.
Martin Laloux, GRANUTOOLS