(564d) Characterization of Powders Spreadability in the Framework of Additive Manufacturing Processes

Metallic and polymer powders are widely used in several Additive Manufacturing (AM) processes, with for example Selective Laser Melting (SLM) and Selective Laser Sintering (SLS). During such operations, successive thin layers of powder are created with a ruler or with a rotating cylinder. Each layer is partially sintered or melted with an energy beam. The layer thickness defines the vertical resolution of the printer, a thin layer leads to a better resolution. In order to obtain a thin layer, the powder is as fine as possible. Unfortunately, when the grain size decreases, the cohesiveness increases and the flowability decreases. The flowability must be good enough to obtain homogenous successive powder layers. The quality of the parts build with AM is thus directly related to the powder flowing properties.

The measurement method based on the rotating drum was used in this paper. It allows indeed to assess the powder spreadability without applying a compressive load during the powder testing what fits with the conditions seen by powder in the AM processes.

Four metallic powders (AlSi7Mg, Scallmaloy, Inconel, Fine inconel) have been studied. Powders spreadability has been determined with the GranuDrum instrument, a rotating drum enabling to quantify the influence of cohesion, shear-thinning/shear-thickening as well as thixotropic behavior. Influence of powders triboelectricity (GranuCharge) and compaction dynamic (GranuPack) have also been investigated. These measurements have been correlated to the powder performance in a SLM 3D printer, where a CCD camera is used to take several snapshots at different recoater speeds (30, 80 and 160mm/s).