The Vertical Roller Mill (VRM) has proven a universal tool for grinding limestone, clinker and slag in the cement industry. The maximum mill powers doubled from 2500 kW in the mid-seventies to 5000 kW in the nineties. Today, another 20 years later, we see 10 MW with a tendency to grow further. As in other industries, unit sizes increase and with this the requirement for equipment availability. Gear technology developed in synchrony with mill power. Starting with the first generation drives featuring bevel parallel shaft gears, the torque passing 1 Mio Nm required torque split. In 1979 forming the second generation of drives emerged featuring a planetary output stage. The current state of the art three stage bevel - planetary gear is the third generation of VRM drives. New fourth generation gear concepts have been proposed and tested to cope with the increasing torques - always with the goal to further improve key performance features.
