LPW Technology develops and supplies customised metal powders for high performance, functional component manufacture, supplying, amongst others, the automotive, aerospace and biomedical industries. It has put in place comprehensive powder testing using the FT4 Powder Rheometer to help engineer powder behaviour for specific AM processes and applications and to ensure a consistent quality product.
“Powder testing is a critical part of what we do, both in the development of new powders and as a service for customers looking to optimise existing AM processes,” said Dr Robert Deffley, research and development manager at LPW Technology. “We’ve long used traditional testing techniques such as angle of repose, but these have inherent limitations. We have seen examples of two powder batches which meet the same specification showing very different behaviour, which made it necessary to look for a new method of characterisation with greater sensitivity. We considered shear cell testers, which are good for silo and hopper specification, but this test alone couldn’t accurately measure powder properties under the conditions needed to provide relevant data for additive manufacture. With the FT4 we still have shear cell capability, if we need it, but also bulk property measurement and, most importantly, dynamic characterisation capability.”
Controlling the performance of powder for AM is crucial for process efficiency and end product quality. How the powder flows and packs, as the layers are formed, are defining aspects of this performance.
“AM is advancing fast and this creates new demands for the powders used,” said Dr Deffley. “AM processes are currently used to produce components with ‘fit and form’, that is prototypes used for advanced product development. The next goal is to robustly engineer in ‘function’ – the controlled porosity for a replacement bone, for example, or complex channels for a more efficient aerospace cooling system. We’re learning that to rigorously cater for these applications we need a more robust understanding of our powders and that these must have tightly-controlled, repeatable behaviour which is consistent from one batch to the next.”
Freeman's FT4 Powder Rheometer is based on measurement of the powder in motion and directly quantifies how the powder flows. Powders can be tested in a consolidated, conditioned, aerated or even fluidised state to fully understand the response to the process conditions.
