An inside look at planetary gears

Planetary gearheads are high-precision, motion-control devices that generate substantial torque for their size, have high torsional stiffness, and low backlash -- making them suited for wide-ranging tasks. A planetary gearhead takes a high-speed, low-torque input, say from an electric motor, then increases torque and reduces speed at the output by the gearhead ratio. This lets motors run at higher, more-efficient rpms in equipment that operates at low speeds. It also reduces inertia reflected back to the motor, increasing stability. And using a planetary gearhead often lets machine builders reduce the size and cost of motion-control hardware. Understanding how different manufacturers measure backlash is important when choosing a gearhead. There are no strict standards regulating how to measure backlash. This can lead to confusion and misconceptions. Some manufacturers measure and average four or more points on the output shaft to produce a backlash specification. Choosing the right gearhead and accurately sizing it is critical to long and reliable life.