Revolution measurements for Additive Manufacturing
Rotating drum rheometers have been widely used to study powders for Additive Manufacturing applications for over 15 years and powders in general for roughly 40 years. The concept of studying powder flow behaviour in a rotating cylinder or “drum” was presented in Kaye et al in 1995. Powder was placed in a clear cylinder with a light source in front of it. An array of photocells was places behind the cylinder. The cylinder or drum was rotated, and the sample powder would prevent or allow light from light source to reach the photocells. In this way, the avalanching behaviour of the powder could be studied. This concept was commercialised under the name Aero-Flow in 1996 by Amherst Process Instruments. As a result of this detection method, the Aero-Flow could only measure the time between avalanches.
The best detection method to study powder in a rotating drum is naturally a digital imaging device. However, in the 1990’s digital imaging devices and processing systems were expensive, and the time required to analyse a single image was roughly 20 to 30 seconds. This situation changed rapidly at the end of the 1990’s with increases in computer processing speed and development of inexpensive digital imaging devices. A commercial instrument using a digital camera to image the powder in the drum was developed by Mercury Scientific Inc. in 2002 and was commercialised under the name Revolution Powder Analyser.
