Why use a gearbox?

Servomotors often drive loads directly without the need for a gearbox, but in many applications it’s advantageous to use a gearbox between the motor and load.

One main reason to use a gearbox is torque multiplication. It lets designers use smaller servosystems that consumes less energy. Instead of buying relatively large servodrives and motors, designer can use smaller components, saving space and money.

Output torque increases in direct proportion to the gear ratio, and top speed of the output shaft decreases. If an application can withstand the reduced speed, a relatively small servosystem can supply high torque.

Gearboxes can also address inertia mismatches. For high performance servosystems — those with high dynamic responses or low overshoot, for example – the ratio between the reflected load inertia and motor inertia should be as low as practical, ideally under ten-to-one. A precision gearbox reduces the reflected inertia by the square of the reduction ratio. For instance, using a 25:1 gearbox reduces the load’s reflected inertia by a factor of 625, a significant improvement.

In some cases, gearboxes simply resolve issues relating to mechanical fit. For example, if directly mounting the motor interferes with another mechanical component, a right-angle gearbox may solve the problem.

Compared to most other gear reducers, a precision gearbox provides better accuracy and repeatability. Furthermore, the gearbox’s high efficiency lets it deliver maximum power available from the servosystem—features often a necessity in servo applications.