Crushing and screening are fundamental processes in mineral processing. Common equipment used in this process includes jaw crushers, impact crushers, fixed screens, and inertial vibrating screens. Below, we will focus on the structural characteristics of a fixed screen with a custom center.

A fixed screen consists of parallel steel bars or rods, called grid bars, connected together by crossbars.

Fixed screens include fixed grid screens, fixed bar screens, cantilever bar screens, and arc screens. Grid screens are installed at the top of the coarse ore bin, primarily to ensure the feed density requirements of the coarse crusher. Large pieces on the screen need to be broken down by hand hammers or other methods to allow them to pass through the screen. They are generally installed horizontally.

Bar screens are mainly used for pre-screening before coarse and medium crushing. They are generally installed at an angle, the angle of inclination should allow the material to slide automatically down the screen surface, i.e., the angle of inclination of the screen bars should be greater than the friction angle of the material against the screen surface. Generally, the inclination angle of a bar screen is 40-50 degrees, and can be smaller for large pieces of ore. For sticky ores, the inclination angle should be slightly larger.

Selection of bar screen apertures: The aperture size of a bar screen is approximately 1.1-1.2 times the size of the particles passing through the screen, and generally the aperture size is not less than 50mm. The width of a bar screen depends on the width of the feed inlet of the feeder, conveyor, and crusher, and should be greater than 2.5 times the size of the large particles in the feed. The length L of the bar screen should be selected based on the width B, generally L=2B. The advantages of a bar screen are its simple structure, no moving parts, and no need for power; the disadvantages are that it is prone to clogging, requires a large height difference, and has unsatisfactory screening efficiency.

Self-centering vibrating screens are suitable for screening medium and fine-grained materials in large and medium-sized plants. The number of screen layers also varies: single-layer and double-layer. They are generally suspended screens, but pedestal screens also exist. Heavy-duty vibrating screens operate on a similar principle to self-centering vibrating screens, but the main shaft of the vibrator is completely stationary; instead, the shaft hole of the pulley is eccentric to achieve self-centering during operation. Heavy-duty mining vibrating screens have a robust structure and can withstand large impact loads. They are mainly used for screening large-sized, high-density materials, with a feed capacity of up to 350mm. They are used for pre-screening before medium crushing. In addition, they can be used for pre-screening and washing of materials with high water and mud content. Oversize material enters the medium crusher, while undersize material enters the washing and desliming system.