The objective of milling is to reduce the particle size of the product to the required fineness.

There are two types of mills to grind the grain:

Cylinder mills, consisting of two or four cylinders, usually ribbed, through which the product to be ground passes. The particle size is controlled by the degree of proximity of the rollers. This mill allows the separation of germ and endosperm and is mainly used in flour mills and semolina mill.
 

Hammer-mills consist of a rotor with hammers that hit the grain against shock plates when turning, thereby reducing the fineness of the product. This type of mill is used for grinding grain in many processes, such as glucose and procurement bio-alcohol from olive mash grinding cereals, feed mill compounds, etc.