Metal powders are used in a wide variety of applications. Many of the items we use on a daily basis include parts molded using metal powders. One parameter to control the quality of the metal powders is particle or powder size, typically in the form of an average value or “Fisher number.”
A common metal powder sizing technique is by air-permeability which gives an average size. Traditionally, a Fisher Model 95 Sub-Sieve Sizer (FSSS), with a particle size range of 0.5 to 50 µm, has been used to get this average size value, or “Fisher number.” Using this technique is the basis for ASTM Standard B330-12, “Standard Test Methods for Estimating Average Particle Size of Metal Powders and Related Compounds Using Air Permeability” as well. Since the FSSS has been discontinued, industry has been clamoring to find an alternative to technique or device that gives the same results and agrees with all the historical data collected on the FSSS.