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Cylindrical mill classification and working principle

The specifications of the cylindrical mill (cylinder scale) are expressed in the cylinder (straight) diameter and inner length (degree) dimensions.
There are many types of mills widely used in industrial production, and the classification methods are also different. Some are classified according to the shape of the grinding medium, some are classified according to the shape of the cylinder, some are classified according to the method of discharging, and some are classified according to the method of grinding production. The main types of various types of mills and the classification methods of cylindrical mills are shown in the following figures and tables.


Figure 1 The main types of mills
A—short tube lattice or overflow type; b—long tube overflow type; c—peripheral discharge type; d—cone overflow type; e—multi-storage (chamber) tube mill

Table   Classification method of cylindrical grinding machine
Grinding machine name
Grinding medium shape
Mill barrel shape
Tube length (degrees) (straight) diameter ratio (L/D)
Mill discharge method
Mill production method
Grinding production circuit
Ball mill
Metal ball
Cylindrical
1~2
Overflow type
Lattice type
Peripheral type
Wind (dry)
Dry or wet production
Open road grinding or closed circuit grinding
Rod mill
Steel rod
Cylindrical
1.5~2.0
Overflow type
Peripheral type
Open type
Open road grinding (rough grinding)
Tube mill
The coarse grinding bin is a metal ball or a steel bar; the last steel segment for the fine grinding bin
Medium and long tubular
2.5~3.5
Overflow type
Lattice type
Wind (dry)
Open road grinding or closed circuit grinding
Multi-barrel tube mill
Long cylinder
3.5~6.0
Self-grinding machine (semi-self-grinding machine) 1
The ore to be ground itself (the maximum block size is generally 300~350mm)
Short cylinder
Generally
0.3~0.5
(1.0~1.2) 2
Lattice type
Wind (dry)
Closed-circuit grinding (rough grinding)
Gravel mill
Gravel or ore (block size 50~100mm)
Cylindrical
Generally
1.3~1.5
Lattice type
Overflow type
Wet production
Closed-circuit grinding (rough grinding operation, using open road grinding)
1 Generally add 4~10% large diameter steel balls; 2 recently made self-grinding machine.
Although the types of mills are different, in general, the basic principles of crushing materials during grinding are similar. In short, when the mill rotates at a certain speed, the grinding medium such as steel balls (rods) or ore (gravel) loaded into the cylinder, the friction between the cylinder liner and the grinding medium The force, the gravity of the grinding medium, and the centrifugal force generated by the rotation of the mill will be lifted to a certain height as the cylinder moves upward, and then the gravity of the grinding medium (actually gravity) When the radial component is greater than or equal to the centrifugal force, it begins to detach from the inner wall of the cylinder and descends according to a certain trajectory. This recurring movement produces a continuous impact and grinding action to comminute the material.
The motion characteristics of the grinding media play a decisive role in the grinding process. The height of the grinding medium and the shape of the falling motion mainly depend on factors such as the structure of the mill, the rotational speed, the shape of the surface of the lining and the filling rate of the medium, and may be in a state of sloping, throwing, pulsating or centrifugal.

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