An interlaboratory study for assessing repeatability and reproducibility of the data generated by rotating drum powder rheometers

Abstract

The National Institute of Standards and Technology (NIST) organized an interlaboratory study to assess the repeatability and reproducibility of the data generated by two commercially available rotating drum powder rheometers namely, Granudrum and Revolution Powder Analyzer. Part 1 of this interlaboratory study focuses on the Granudrum rheometer. In total, thirteen laboratories comprised of industry, academia, and a national laboratory participated in this study. A nickel-based alloy, a titanium alloy, and a stainless-steel alloy in powder forms were tested, and an analysis of variance (ANOVA) model was used to rank the contributions of the study factors to the observed variability in the data. First, a maximum of five study factors were considered: material, sample, rotation speed, test, and participant (lab), which provides the ability to assess interactions, such as between lab and rotation speed and lab and material. The ANOVA results indicate that the ‘Flow Angle’ data showed 6% of its variation attributable to repeatability and 5% to reproducibility, whereas the ‘Cohesive Index’ data showed 21% of its variation attributable to repeatability and 17% to reproducibility. Next, because using the different rotation speeds and materials can add significant variability to the overall data, we also present separate ANOVA results for each combination of rotation speed and material. These results provide further insight into the repeatability and reproducibility of the Granudrum-generated data.