Classifier are sometimes known as screeners or pellet sifters. They are used for quality control purposes in pelletizing and compounding operations. The classifier is comprised of vibrating decks with different sized screens. The newly created plastic pellets from the extruder are dropped into the classifier. As they are shaken on the screen the smaller pellets drop through the screen and are discharged one direction. The larger pellets are conveyed in another direction and discharged. If further reduction is needed there can be another screen. Classifiers can be rectangular or round and are sized via length x width or the diameter of the screens. If the machines has one deck/screen it is considered two-separation classifier. If the machine has two decks/screens it is considered a three-separation machine.
Typical Brands of Classifier include Sweco, Witte, and MGB.