True density is an inherent property of a material, whilst apparent density takes account of occluded voids within a material. Having knowledge of the true and / or apparent density of a material feedstock is important to the powder bed formation and sintering kinetics as well as the porosity, or indeed lack of porosity in the final product.
Bulk density is influenced principally by the distribution of particle sizes and shapes. Bulk density is important in establishing material specifications and can give confidence regarding powder flowability and bed formation.
Envelope density is based on the geometric volume of a sample and is useful when characterizing the end product as it can measure the volume of intricate and irregular end product. When combined with the true density from the AccuPyc measurement porosity can be determined quickly and easily.
The AccuPyc II 1340 Helium Pycnometer and GeoPyc 1365 Envelope and T.A.P Density Analyzer from Micromeritics permit the user to determine key density and porosity measurements needed to standardize process parameters, qualify and approve supplied vendor raw materials, as well as an indicator to the end product quality. Both instruments utilize non-destructive testing methods and when used in tandem can indicate total porosity of the metal powder.