Very high drive efficiency & low maintenance requirements


The experience gained from installation and operation of these mills enables us to offer mills of up to 35,000 installed horsepower or more.

Today a single grinding line with a Gearless SAG mill and appropriate ball mills can process over 100,000 mtpd.


  • Variable speed capability
  • Removal of limits of design power gear and pinion drives are practically limited to about 10,000 hp per pinion. at this time, there is no reasonable gear drive alternative for more than two pinions or above 20,000 hp. the best solution is the Metso gearless mill.
  • Very high drive efficiency
  • Low maintenance requirements
  • Often require less floor space




Autogenous (AG) grinding is the size reduction of material in a tumbling mill utilizing the feed material itself as grinding media. Semi-Autogenous (SAG) grinding is the size reduction of material in a tumbling mill utilizing the feed material plus supplemental grinding media. The most common supplementary medium is steel balls.

Gearless drives (ringmotors) have been used on tumbling mills for several decades. The design features motor rotor elements bolted to a mill shell, a stationary stator assembly surrounds the rotor elements, and electronics covert the incoming current from 50/60 Hertz to about 1 Hertz. The mill shell actually becomes the rotating element of a large low speed synchronous motor. Mill speed is varied by changing the frequency of the current to the motor. The ringmotor can be used to inch and spot the mill for maintenance.

Our engineers welcome the opportunity to assist you with circuit and circuit control design as well as start-up, operation, and optimization of the milling plant.

Previously viewed products