Rod mills are more like ball mills that works to pulverize hard materials into smaller pieces. The only difference is that with rod mills, long rods are employed to grind hard materials. Rod mills pulverize materials by grinding with other materials inside the mill just like how ball mills grind against the materials fed into the machine.
In order to prevent rod charge tangling incidents, the length to diameter ratio of rods are kept at 1.4 to 1.6. A rod mill can take feed for about 50 mm or 2 in. and produce an output that ranges from 3000 to 270 mm or -4 to -35 mesh. Grinding is done thru line contact between the rods that extend all throughout the length of the mill. Rods work by tumbling and spinning in rough parallel alignments the way a series of roll crushers work. The result is high quality grinding product out of hard and coarse material with minimal slime production.
There are three types of rod mills. There is the overflow mill, the end peripheral discharge and the center peripheral discharge. Of the three main types, the overflow mill is widely used. Rod mills are also categorized into two; the wet grinding mills and the dry grinding mills. Wet grinding mills are utilized in industries involved in mineral processing while the dry versions of grinding rod mills are used in other purposes. Of the two, dry grinding usually encounters issues and where possible, it is recommended to avoid having the equipment unless necessary.
Rod mills offer a lot of advantages to users but compared to ball mills, they run at lower speed because the rods had to be rolled out by the machine instead of cascading. However, the rod mill utilizes less steel during production compared to a ball mill due to its lower speed thereby creating better contact between the grinding material and the ore.
To ensure optimum performance of your rod mill, make it a point to remove broken rods including the worn out ones. Only employ qualified rod mills technicians for rod replacement and repairs of the equipment.