Ball Mill Grates | 6-30mm Aperture Panels | ATF

Ball Mill Grates: Discharge Control for Grate Mills

Grate discharge ball mills use perforated grate panels to control the discharge of ground material while retaining grinding media inside the mill chamber. The grate aperture size—typically ranging from 6 mm to 30 mm depending on the grinding circuit—determines the maximum particle size that can pass into the discharge. Pulp lifters mounted behind the grate panels transport the classified slurry radially from the grate face to the discharge trunnion, enabling continuous removal of ground product. ATF manufactures grate panels from ASTM A532 chrome-moly steel (350–450 BHN) for standard abrasive applications, high-chrome white iron (600+ BHN) for maximum wear resistance, and natural rubber (60–70 Shore A) for anti-pegging performance in sticky or corrosive slurry environments. Each grate panel is precision-cast or machined to maintain consistent aperture dimensions across the full discharge face.

Grate design directly affects both product sizing accuracy and mill throughput capacity. Smaller apertures produce finer product but may restrict discharge capacity and increase the risk of pegging (aperture blockage by near-size particles), while larger apertures increase throughput but allow coarser particles to discharge, potentially overloading downstream classification equipment. The grate open area—typically 15–40% of the total panel surface—must balance these competing demands. Tapered slot profiles, where the aperture widens from the grinding face to the discharge side, improve slurry flow and reduce plugging compared with parallel-sided slots. ATF engineers grate systems optimised for your specific circuit requirements, considering target P80, ore characteristics, media size, slurry density, and downstream classifier capacity to deliver the best balance of throughput, product quality, and campaign life.