In a dual stage hammer mill, there are really three phases of size reduction, due to what is known as the attrition zone. The attrition zone is the area created between the top rotor and bottom rotor of a dual stage hammer mill. Materials pass through the initial mill and screen arrangement and are then directed toward the secondary mill chamber.
The particle grinding mechanism in stirred milling is almost 100% attrition or shear type grinding, , rather than impact grinding as occurs in tumbling mills, like SAG and ball mills. Large particles can be efficiently reduced in size by impact grinding where the breakage method is shattering of particles by direct fall upon them from crushing bodies, like steel balls in a tumbling mill.
The Mikro® UMP Attrition Mill is a high speed cutting mill designed for the fine size reduction of plastics, waxes, and fibrous materials that do not respond well to other forms of impact milling. It is designed to grind heat sensitive and soft materials without liquid nitrogen or conditioned air. The video describes the features of the mill and the processing of polyethylene chips.
High speed impact mill with exchangeable grinding tools for the grinding of soft to medium hard materials Grinding takes place in a vertical Rotor/Stator System in numerous variations: Beater Mill. Blast Mill. Pin Mill (single rotating and counter rotating. Attrition Disc Mill.
The milling rate constant for an attrition mill is sensitive to changes in rotor velocity and increases linearly with the power input to the mill. The amount of medium present also influences the milling rate constant.