When does a Servo Motor Combine with a Gear Reducer?

In modern industrial equipment, particularly when using in the high precision conditions, the servo motor technology is developed into high torque density, as a result, the rotation speed may be up to more than 3000 rpm. With the improvement of rotation speed, power density of servo motor is also greatly improved, that means whether a servo motor needs to be matched with a speed reducer gearbox is mainly determined by the application need and the cost. In following application conditions, a servo planetary reducer gearbox is needed.

Heavy load and high precision
The servo planetary gearbox is needed when the load must be moved under precision position requirement. Generally, the equipment involved are automation equipment, such as aviation, satellite, medical, military technology, wafer equipment, robots. The common characteristic for them is that the torque required to move the load generally far exceeds the torque capacity of the servo motor itself. Using a gear reducer to improve the output torque of the servo motor can effectively solve this problem.

Increase the torque
Output torque can be increased by directly increasing output torque of the servo motor, however, such a mode not only requires an expensive high power servo motor, the motor shall also have stronger structures. The increase of torque is proportional to the increase of control current, if a larger driver is used, the increase of specifications of power electronic components and related electromechanical equipment will greatly increase the cost of the control system.

Improve service performance
It's reported that improper matching of load inertia is one of the biggest reasons for unstable servo control. For a large load inertia, the best equivalent load inertia can be allocated by the square inverse ratio of the reduction ratio, so as to obtain the best control response. On this view, planetary speed reducer is the best match for control response of servo applications.

Reduce equipment cost
From the cost perspective, if the AC servo motor of 400W consumes one unit of equipment cost when it's equipped with a driver, then the AC servo motor of 5.5KW consumes 15 units of equipment cost when it's equipped with a servo driver. However, if a servo motor of 0.4KW and a driver complete the task of above combination that consumes 15 units of cost when they are equipped with a reducer, then the operation cost will be reduced for more than 50%.

In summary, planetary speed gear reducer shall be selected according to different machining demands. Generally, if the equipment is used in low speed, high torque or high power density conditions, the planetary gear reducer will be adopted.