Powders have always been used in industry, spanning from food to metallurgic ones, and in recent decades they have become the protagonists of other innovative process: additive manufacturing (AM). Knowing the flowability of a powder in a specific piece of equipment is fundamental to achieve better manufacturing efficiency and product quality in powder processing industries. A powder used in AM machines is subjected to different flow and stress regimes. There are commercial devices able to measure the flowability of the powder under different levels of consolidation stresses, but they are not able to work at very low stresses. Among the available, alternative, non-commercial tests dynamic BIM is the most promising. In dynamic BIM a spherical indenter impinges on the powder with the velocity of a falling body; it is possible to determine the flowability (through the hardness) of the powder, but the evaluation is complex and must be improved. In this work we investigate the dynamic impact of an indenter in a packed powder, measuring the geometrical characteristic of the crater forming on the powder surface. Furthermore, we try to improve the definition of dynamic hardness and shear rate by rewriting them in terms of granular velocity rather than indenter impact velocity as the most common reports in the literature.
Characterization of Powder Flowability for Additive Manufacturing
Santomaso A. C.
2023
Abstract
Powders have always been used in industry, spanning from food to metallurgic ones, and in recent decades they have become the protagonists of other innovative process: additive manufacturing (AM). Knowing the flowability of a powder in a specific piece of equipment is fundamental to achieve better manufacturing efficiency and product quality in powder processing industries. A powder used in AM machines is subjected to different flow and stress regimes. There are commercial devices able to measure the flowability of the powder under different levels of consolidation stresses, but they are not able to work at very low stresses. Among the available, alternative, non-commercial tests dynamic BIM is the most promising. In dynamic BIM a spherical indenter impinges on the powder with the velocity of a falling body; it is possible to determine the flowability (through the hardness) of the powder, but the evaluation is complex and must be improved. In this work we investigate the dynamic impact of an indenter in a packed powder, measuring the geometrical characteristic of the crater forming on the powder surface. Furthermore, we try to improve the definition of dynamic hardness and shear rate by rewriting them in terms of granular velocity rather than indenter impact velocity as the most common reports in the literature.
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