Ball mills are giant drums that are filled to between 30 and 40% of their volume with freely moving grinding media - in this case balls. The diameter of the balls is between one and several centimetres to suit the application - smaller balls for fine milling results and larger ones for coarser milling tasks.

The drive sets the milling drum into slow rotation and the bed of milling media is thus activated, i.e. the balls are lifted and then impact back against the bed. Ball mills are usually operated below the critical speed. The critical speed is the speed where, mathematically calculated, the grinding media would centrifuge out.

A mill of this size equipped with steel grinding media converts approx. 50 kW per m³ of feedstock. The feed product is fed continuously through the trunnion and is discharged through slots on the opposite side. The discharge rate can be adjusted as a function of the number of open slots. The ground product is transported - often pneumatically - and is charged to a downstream classifier. The coarse material is returned to the mill together with the feed product.

The classic standard design which has proved itself in operation throughout the world for decades. Both the design and efficiency are continually improved to pay tribute to new technology and market requirements.

• Cast side plates bolted to a rolled-steel drum with integrated manhole
• Drive via ring-and-pinion gear with automatically controlled tooth lubrication, back gearing with couplings and high-performance gear unit
• Bearing unit: journal bearing designed as a friction bearing with permanent oil-recirculation, lubrication and temperature control
• Option: self-aligning roller bearings
• Product discharge via adjustable slots located around the periphery of the drum. Two-part discharge housing with top venting connection and inspection cover

Ball mills are usually operated below the critical speed, i.e. in the fringe area between cascading and free-fall. With a specially designed frequency converter, it is even possible to operate a heavy ball mill at variable speed. And if the S.O.-SF is to be used for grinding ultrafine products or if it is planned to change the product frequently, operation with a frequency converter is particularly advantageous.

A high consistency of the product quality demands exact measurement of the amount of product in the mill. Because of this, an optional accessory offered for our ball mills is the load cell system which permits precision control of the product level. The complete ball mill is bedded on a steel or concrete frame designed to rest on a defined number of load cells. The load cells are integrated into a control unit and determine the total weight of mill, grinding media and product. The addition of virgin feed can be controlled with such precision that the mill always operates at optimum load. This means reliable prevention of no-load operation or overfilling, and mill operation is exceedingly cost-effective.