Grinder

Grinder of a mill in Marienburg .

Grinder is the name for a functional unit or an aggregate for grinding ( comminuting ) substances in mills , e.g. B. in grain mills or oil mills , but also in the household in the pepper , salt or coffee grinder .

Modern grinders usually consist of metallic tools, more rarely also of corundum (household grain mills ). The grinding effect is achieved by multiple crushing in an increasingly narrowing grinding gap, which can usually be varied by axially displacing the rotor or stator. Milling is done by shearing and / or friction. Other grinding systems are roller mills , impact and impact mills.

In roller mills, the material is crushed between cylindrical grooved or (rough) smooth rollers that rotate at different speeds (advance).

In impact mills, the material to be ground is crushed by single or multiple impacts by being gripped by the very fast rotating grinding tools (up to 11,000 min ⁻¹ or 250 m / s). There are also mills with counter-rotating rotors , with rotor and stator and only with rotor.

During grinding , the grist is ground between the millstones.