DC servo motors very often come in for repair because their brushes have worn out. This seems like a straight forward problem with an easy solution; install new brushes! And while this could be true, premature brush wear can be a sign of larger problems with your servo motor. There are a few points you can check to narrow down the cause of your premature brush wear.

Check Your Brush

Is the Head of the Brush Broken or Chipped?

If it is then your could have a high bar or piece of mica on your commutator which means you will need to clean up your comm or possibly rewind your armature.

Are There Grooves in the Brushes?

If there are thin grooves in the brush then there are probably matching thin grooves in the commutator. This problem is called threading because the grooves resemble the threads of a bolt. This could be an indicator that you have the wrong type of brushes installed or are running the motor with too light a load. This is a common problem with long life brushes.

Does the Brush Show Signs of Burning or Arcing?

If the servo motor’s electrical neutral is not properly set then there will be voltage potential between the brush and the commutator bar before the brush is contacting that bar, which will cause arcing when they get close to each other.

In Summary

Servotech uses Helwig brushes for almost all of our servo motor repairs. Knowing why your brushes are wearing will help you determine if your DC servo motor needs repair or if you can modify the brushes you use and save money and downtime.