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Hearing servo sounds like knocking, or your servo motor has a strong vibration? You send it somewhere for repair and you are told that the bearing fit is no good. You get a quote to change the bearings and repair the bearing fit. Problem solved, you say… Then your servo is returned and fails again. What is so difficult about fixing a bearing fit?
Bearing Considerations
Why Bearings Fail
- Fit is incorrect bore.
- Bearing was incorrectly installed.
- For a variety of reasons, bearing seized.
Failed Bearings Cause Other Issues
- Encoder glass may be damaged by oscillation.
- Resolver windings break if not on central axis.
- Shaft may break under armature, hidden.
- Rotor may hit stator if air gap is altered.
- Laminations may bend and pinch coil.
- Pinched coil may result in shorted windings.
- Bent laminations may rub, causing extra wear.
Avoid Multiple Repairs
- Call 1-866-80SERVO.
Why Is the Bearing Fit Failing?
Failure of a bearing fit is a common problem with all electric motors. Bearing fits fail when the fit is not the correct bore, the bearing was incorrectly installed, or the bearing seized. If a bearing fit fails this can lead to many other problems with your servo motor.
Feedback Devices Are Damaged Easily by Oscillation
Feedback devices are very sensitive. Encoders often have glass scales that shatter and resolvers have windings that are damaged when their axis of rotation is not perfectly central.
Rotor Shafts Can Bend or Break
Servos need to run true and broken shafts can occur under the armature where they are often missed until the motor is under load in your machine.
Damaged Stator Laminations Ground Power Leads
The air gap between rotor and stator is small, so when there is an oscillation in the rotor it will bang into the stator laminations. Bending the laminations can cause high spots that rub and also cause the lamination to pinch the coil under it shorting the motor windings to ground.
Who Can Repair the Bearing Fit Once and for All?
When your servo motor has a failed bearing fit be cautious where you have it repaired. Regular motor shops will not be capable of evaluating or repairing the feedback on your servo. Most places will see a failed fit and look no further. Being aware of the side effects of a bad fit will improve the likelihood that your servo gets properly repaired the first time.
Servotech has the tools and knowledge to solve this problem. Call 1-866-80SERVO to discuss your issue with us.
