Servo Motor Ball Bearing - Choosing the Right Actuator

Servo Motor Ball Bearing is utilized in applications such as machine tools, robots, and carrier equipment where precise motion control is vital. This type of application places a great deal of strain on the motor, especially as it has to stop and start, and reverse while operating under constant vibrations. This can cause fretting damage to the ball bearing, reducing the life of the bearing.

In addition, the speed range of these motors is very high. This also increases the possibility of oscillation, which can lead to a loss of position accuracy and positioning reliability. This is a major cause of the premature failure of many servomotors.

It is important to understand the effects of these conditions on servo motors in order to select the correct actuator for your application. Servo motors are expected to run for extended periods of time, requiring them to work under constant stress and exposing them to natural wear. Factors like dirt, grease, and environmental temperatures can drastically decrease the lifespan of a servo motor, so selecting the proper model for your application is crucial to ensure optimum performance.

There are several different types of actuators that can be used with a servo motor including belt, rack and pinion and screw. All of these mechanisms have moving parts that produce backlash, stiffness and vibration, which degrades performance over time. These mechanical systems are typically sized to a load to motor inertia ratio, which is the maximum amount of inertia that can be controlled with the motor based on the mass of the load. This inertia is measured through the encoder of the motor, which reports the position to the control system.

The most stable of these actuators is the screw-driven mechanism, which can achieve a very high level of position stability due to its high inherent rigidity. However, there is a critical speed at which the screw will begin to vibrate and oscillate. This is caused by a combination of the friction between the nut and the shaft, as well as the inertia of the servo motor itself. Servo motors with higher acceleration ratings have the ability to overcome this constraint, but it is still recommended that an engineer evaluate this option carefully.

Choosing the right actuator requires consideration of the load capacity, drive, mounting method, and lubrication requirements. Heavy loads should be left to roller or cylindrical bearings, while lighter loads can be accommodated by angular contact balls or semi-metallic bearings. The direction and magnitude of the driving force must also be evaluated as this will impact shaft float and bearing arrangements. A belt or gear take-off can place greater axial loads than a coupling drive, which may require consideration of additional shaft shims to maintain the necessary alignment. Lastly, vertical mounting is always a concern and should be evaluated to make sure that the appropriate bearing arrangement is selected.