How to Relate the Spreadability of Powder to the Layer Homogeneity in Powder Bed Fusion Additive Manufacturing - 2022

How to Relate the Spreadability of Powder to the Layer Homogeneity in Powder Bed Fusion Additive Manufacturing: A Correlation between Cohesion Assessments and In Situ Printer Measurements

Metallic powders are widely used in additive manufacturing processes with, for example, selective laser melting and selective laser sintering. During such operations, successive thin layers of powder are created with a ruler or with a rotating cylinder and then partially sintered or melted with an energy beam. Thin layers of only tens of microns high are usually required to guarantee sufficient vertical resolution as well as good mechanical properties of the final parts. Unfortunately, when the particle size decreases, the cohesiveness increases and the spreadability decreases. Consequently, the spreadability must be good enough to obtain homogenous successive layers. Relating the powder characteristics to spreadability during the recoating process beforehand should provide a more cost-effective way to classify and select the optimal powder and recoating speed combinations. In this study, the flowability of metal powders has been investigated with a rotating drum measurement principle. These measurements have been correlated to the powder spreadability during recoating evaluated directly inside an selective laser melting printer. Results show that the cohesive nature of the powder is a key parameter defining its spreading performance during the recoating.

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