Gear motors are used for precision positioning tasks to provide higher torques and higher resolutions at lower speeds. In slow applications, the rotor moves comparably fast thanks to the gear ratio. Without gears, undesired cogging torques may occur due to the low rotor speed. Moreover, gears support the holding forces in vertical applications. Often, less effort is required for the control loop because, thanks to the gearhead, the motor is only subject to a load on the motion platform that is reduced by the square of the transmission ratio.
However, a geared motor is not play-free and additional friction reduces efficiency. For this reason, gear manufacturers often offer suitable lubrication to guarantee the expected lifetime. The lifetime is subject mainly to input speed and output torque as well as operating, ambient, and installation conditions. In customized solutions, the lifetime can be prolonged by self-lubricating bearings, ball or ceramic bearings, metal gearwheels, and special greases.
Strictly speaking, drive screws also act as gears in gear spindle positioning systems because speed adjustments are achieved on the expense of the torque in dependence of the spindle pitch. To this effect, a motion platform moves twice as fast at 50% of the torque with a spindle pitch of 2 mm/revolution compared to a spindle pitch of 1 mm/revolution. For some applications, however, an actual gear is required to act between motor and drive screw. PI deploys various gear types for this scenario.