Powder flowability is one of the most challenging topics in powder characterization for AM users. The problem starts with defining what “flowability” means, then how best to measure it. This problem is, of course, not unique to the AM industry. Virtually every industry handles, stores and processes powders and other bulk solids. Applications range from small hoppers used to feed tableting presses in the pharmaceutical industry to huge silos used to store grain, coal and other bulk solids.
The authors identify fundamental flowability concepts and key parameters, then describe the various means by which those parameters are measured. They differentiate between tests that are used to qualitatively compare various powders from tests that measure their basic flow properties that can be used for design. The latter include tests to measure a powder’s cohesive strength, internal and wall friction, compressibility, permeability and segregation potential.
Examples are provided of tests conducted on various AM powders and how this data is used in other industries that can be applied to AM applications.