During the cleaning and sieving process, foreign objects are removed from the raw material.  

Pre-cleaners such as magnets and drum sieves are used to protect the equipment from foreign objects. In feed mills, they are used during the raw material intake process. After arrival at the mill, the raw material is sent to the pre-cleaners.
 
 Magnets are controlled by the external pneumatic pistons. Product outlets and metal collection outlets are separated by a valve. After the raw material is placed into the machine, the metals in the material are trapped by the magnets as the material passes through the magnetic surface.
 
 Drum sieves are used for rough cleaning of the raw material. They separate the raw material from large lumps, wooden objects, stones, nylon, yarn and other foreign objects.
     
Vibrating sieves are mainly used for two different purposes: cleaning before the grinding process and cleaning the pellet that comes out of the pellet mill.

Centrifugal sieves are used for controlling the size of small grains after the grinding process. Small grains pass through the sieve to continue the process while large ones are sent to the garbage bin by the rotor.