Basically screening theory
Screening refers to a method of classifying materials according to their particle size. As one of most effective method of material classification, trommel screen is widely used for mining, metallurgy, chemical, construction, environment protection and other industries.

Motion analysis for the particle on the screen deck
When the material particles move with the screen deck, the material screening process can be finished. The movement form of material particles on the screen deck determines the final screening effect of the screening equipment. Seeking the best kinematics parameters by studying and analyzing the movement rules of materials in the screening process. It is a great significance to play the best screening effect and improve the screening efficiency of screening equipment. There are two kinds of particle motion theory, the single particle movement theory and particle group motion theory. The trommel is the key part of the trommel screen. When the trommel screen running, the trommel rotates around its shaft. The motion trail of particles in the trommel is mainly divided into three stages: ascending, separating and parabolic motion.
Material filling rate
The computing method of the capacity for trommel screen is by the volume of material rather than the quantity of material. In other words, for the trommel screen, the processing capacity is the volume of material processed in a unit of time, rather than the amount of material processed. Therefore, the filling rate of materials in the roller has a great impact on the handling capacity of the roller. In addition, the material filling rate has influence for the screening efficiency of the trommel screen. When the filling rate of the material is small, the thickness of the material is small, so the particles have more opportunities to contact with the roller, and its screening probability is greater, so that the material in the trommel screen has a higher screening opportunity. This also led to the low processing capacity of the trommel screen. When the filling rate of material is larger that can increase the volume of the material, but the material layer is thicker, and the contact between the material and the screen surface is less. Some materials cannot contact the screen surface in the whole process of particle movement, which will reduce the screening efficiency of the trommel screen. Therefore, it is very important to select the best material filling rate for the trommel screen to maximize the potential energy of the equipment.
For the different characteristic and structure material, the best filling rate to be used is also different. The optimum material filling rate of the trommel screen should depend on the characteristics of the material, the required screening efficiency and the condition of the trommel screen. Generally speaking, the optimal material filling rate is 20%-30%.
Trommel inclination
Another important design parameter is the trommel inclination. Compared with the material fill rate, the incline angle of the trommel screen has a large effect on the screening efficiency and capacity. The greater the trommel inclination, the greater the forward speed of the material along the axis of the roller. This allows the material to pass through the roller quickly, while also increasing the screening capacity. However, the number of contacts between the material and the screen is small, as a result, the screening efficiency is low. When the installation angle is small, the movement time of the material in the roller becomes longer, the contact time between the material particles and the screen surface becomes more, the processing precision becomes higher, but the processing ability is lowered. When the material filling rate and the inclination angle are the same, the screening efficiency is closely related to the performance of the material, the roller screen, and the like. Normally, the angle of inclination of the roller should be 5°~8°.
Diameter of roller
The screening capacity of the trommel screen is also related to the size of the roller diameter. When the filling rate of the trommel screen is determinded, the larger the diameter of the roller, the screening capacity of the trommel screen will be greater. At the same time, the optimum working speed of the trommel screen is also related to the diameter of the roller. The larger the diameter of the roller, the rotation speed of the roller will be smaller.