The material enters the classifier through a feed inlet at its lower end and is then propelled upwards by suction from a fan. As it passes through the classifier, it is subjected to strong centrifugal forces generated by a rapidly rotating turbine. Qualified fine powders pass through blade on the classifier into a cyclone separators or dust collector for collection. Some fine powders carried by course particles collide with walls and fall back down towards secondary air inlets along the cylinder wall. Coarse particles are separated from finer ones due to strong elutriation from secondary air flow; fine particles rise up for further grinding while coarse ones fall out at discharge ports.