| Résumé | Powder spreadability significantly affects the reliability and productivity of various additive manufacturing (AM) processes, including laser-beam powder-bed-fusion (PBF-LB) processing. Part quality relies on the uniformity of the powder layer density within a build and on the reproducibility between builds. Moreover, the overall process productivity is affected by the capability to spread the powder layers quickly and uniformly; both are highly dependent on the powder flowability.
The correspondence between powder performance in powder-bed-fusion machines and powder flowability measured with standard methods (MPIF,1 ATSM2 and ISO3) is not always clear and the America Makes & ANSI AMSC Standardization Roadmap for Additive Manufacturing4 recently reported that existing standards for flowability do not account for the range of conditions that a powder may encounter during AM processes. Consequently, there is a necessity to develop and validate other characterization methods adapted for the specific needs of additive manufacturing.
Powder flowability can be influenced by environmental and handling conditions such as humidity, temperature, and atmosphere. Powder flowability is also affected by many powder characteristics such as the density, the particle-size distribution (PSD), and morphology, the presence of satellites, and surface characteristics. As most of these characteristics can be modified during the AM build and recycling processes, monitoring the powder behavior is essential. |
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