Hopper design for metallic powders used in additive manufacturing processes

Abstract

The influence of hopper geometry on the flow behaviour of typical metallic powders used in additive manufacturing processes is investigated. Bulk hopper theory provides a method of determining critical hopper parameters for bulk amounts of particulate solids to be stored and discharged out of hoppers. Bulk hopper theory proves to be unsuitable for the additive manufacturing process. The discharge rate of powder out of the hopper is as important as the flow / no-flow criteria used for bulk hopper theory. Additive manufacturing requires the controlled delivery of small amounts of powder onto a bed in a homogenous layer that is usually less than 100 µm thick. Powder flow behaviour of different metal alloys with particle diameters in the range of 20 – 90 µm is investigated. Powder volumetric flow rates as a function of hopper outlet width is determined. The results obtained through experimentation are presented in the form of empirical equations.