In the grinding process of metal concentrators, the structural design of ball mills directly determines their adaptability to different grinding tasks. Among the two core types—overflow ball mills and grid-type ball mills—each has a unique structural layout tailored to its functional positioning, from the thickness of the cylinder steel plate to the details of the discharge component.
Starting with the overflow ball mill, its structure is a model of simplicity and practicality, consisting of six key parts: cylinder, end covers, main bearings, hollow journals, transmission gears, and ore feeders. The cylinder, the "core working chamber," is welded with 15-36mm thick steel plates—this thickness is not arbitrary. Thinner plates (15-20mm) are used for small-scale mills handling low-hardness ores, as they reduce equipment weight and energy consumption; thicker plates (25-36mm) are reserved for large-scale mills processing high-hardness minerals like iron ore, ensuring durability under long-term impact. Both ends of the cylinder are equipped with flanges that fit precisely with the end covers, minimizing pulp leakage during operation—a detail that directly affects grinding efficiency and environmental cleanliness.
The hollow journals, which connect the end covers and support the entire mill, are another structural highlight. The journal near the transmission gear ring is fixed with a shoulder, while the other can expand and contract freely. This "fixed + flexible" design addresses a common problem in mill operation: when the cylinder heats up due to friction during grinding or bears uneven loads, the free journal can adjust its position to avoid structural deformation. Additionally, the inner diameter of the discharge-end hollow journal is slightly larger than that of the feed end, and some models are equipped with reverse spiral blades. These blades act as a "filter": they prevent unground coarse-grained materials from being discharged prematurely and stop small steel balls (critical for fine grinding) from being lost with the pulp, ensuring the mill maintains stable grinding performance.
The grid-type ball mill shares most structural components with the overflow type but differs significantly in the discharge end—its "secret weapon" is the added discharge grid plate. The end cover is divided into eight fan-shaped chambers by radial ribs, each fitted with a dustpan-shaped lining plate. On these lining plates, two groups of grid lining plates are fixed with wedge irons, forming a forced discharge structure. The dustpan-shaped lining plate guides the pulp to the grid plate, while the wedge iron fixation ensures the grid plate withstands the impact of steel balls and pulp without loosening. This structural upgrade transforms the discharge method from "free flow" to "forced discharge," making the grid-type mill uniquely suited for coarse grinding tasks.
From the thickness of the cylinder to the design of the discharge grid, every structural detail of these two ball mills is a result of matching specific grinding needs. Understanding these structural differences is the first step in selecting the right equipment for a concentrator.
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