The grid screen is the simplest cleaning equipment. The main function is to prevent large impurities such as mud, stones and ropes from entering the material discharge hole, preventing blockage of the discharge hole and the later conveying and other processing equipment; it also prevents the feeding personnel from falling into the material feeding inlet to protect personnel safety. The grid screen is the first cleaning equipment, and almost every feeding inlet should be set up, such as in the main and auxiliary material feeding inlet of the main workshop, and the manual adding inlet of the additive next to the batching scale, etc. The gap of the grid screen should be determined according to different discharge ports and different materials. For example, the gap between the grids in the feed main workshop for corn and powdery auxiliary materials is about 30 mm. In the corn feed port in front of the vertical storage silo, because of the large output required, the gap between the grids can be larger. For the cake materials, due to its poor scattering, the gap between the grids should be about 40 mm. The grid screen should be fixed at the feeding port and ensure an inclination angle of 8 to 10 degrees, so as to pour out the material in the bag and reduce the labor intensity of the feeding. The cleaner is the main equipment for the cleaning of impurities of the feed mill. Commonly used are the drum cleaner, powder cleaner and vibrating cleaner. Drum cleaner is mainly used to clean granular raw materials, such as corn cob, hemp rope, cloth, stone, clods, straw and so on. Drum cleaner is not suitable for the powder, mainly because the powder is less scattered than the particles, and it is easy to accumulate and block on the chute of the feeding, so that the production cannot be smoothly carried out. The drum cleaner has the characteristics of simple structure, small volume, large output, low power, convenient installation and maintenance, etc. According to the nature of the material, the sieve cylinder with suitable sieve hole can be selected. Vibrating cleaner can be used for the cleaning of granular materials and for the cleaning of powdered materials. As a cleaning screen, it can effectively remove large impurities in the raw material. The device changes the screen surface from above, which saves the space occupied by the screen change, and the screen surface is fixed by the buckle, so the screen change operation is very convenient. As a cleaning sieve, vibrating cleaner has strong adaptability to materials and high impurity removal efficiency, but the discharge port is small and sometimes has poor discharging of impurities; For the same amount of processing, its power consumption and larger floor space cover, the price is higher and it is easy to produce noise and vibration. Magnetic separation equipment can be divided into electromagnetic equipment and permanent magnet equipment according to the type of magnet. When power off, the iron miscellaneous in the electromagnetic equipment will fall into the material and it is inconvenient to use. Therefore, the feed mill now uses permanent magnet equipment.