DC Brushed servo rebuildable?

[tjs88yj]

I have a Hurco SM1 that I believe has a bad Z axis motor. I am in the process of retrofitting the control and have the X & Y axis up and running, but can't get the Z to do anything but trip the current fault on the servo drive. I've swapped the X encoder to the Z and had no change, I've swapped servo drives no change, I took the Z axis motor and connected it to the Y axis wiring and no change. This leads me to believe that the motor is the issue. Is there anything I can do to definately prove the motor is my issue?

If it is the motor is it rebuildable? I know I can replace the brushes, but is that all I need to do? Thanks

Tom

[Al_The_Man]

You need to take the end cover off and expose the Commutator and brush gear.
Look for build up of carbon and blow out if necessary, and commutator appearance, it should be smooth with no pits are sign of severe arcing.
Look for overheated/burnt armature windings.
You could try running it on a automotive battery, it should run up to speed easily with no growling or arcing etc.
Al.
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[tjs88yj]

Thanks for the quick reply AL. This is an older servo motor with a tach, I have removed the tach brushes since I am not using the tach. Will I have to disassemble the tach end of the motor to get to the items in your reply?

Thanks

[Al_The_Man]

Most tach's are built onto the shaft so you virtually have to remove the armature for a complete check. Other than that you can some times just remove the brushes to blow it out and examine the comm, through the brush slots.
Removing and replacing the armature can be tricky due to the strong attraction of the magnets.
Al.

[TOTALLYRC]

Originally Posted by Al_The_Man You need to take the end cover off and expose the Commutator and brush gear. Look for build up of carbon and blow out if necessary, and commutator appearance, it should be smooth with no pits are sign of severe arcing. Look for overheated/burnt armature windings. You could try running it on a automotive battery, it should run up to speed easily with no growling or arcing etc. Al. ,

Be careful when blowing out a dc motor, you do not want to get a lung full of the brush dust, as it is not good for you and can cause breathing problems. The brushes many times are more than just carbon, some have metals in them.

When I worked in the motor shop, we used to hot water wash the motor after dissassembly and then bake at ~200 IIRC degrees for 8hrs IIRC or so to make sure no water remained.

Since you are doing a one off rebuild, I would suggest the use of an electric motor cleaning solvent, taking all of the proper precautions and disposing of the run off properly, according to the label directions.

Al is right in that the motor should run at a slow speed with no jitter, noise or other issue's on 12v. Make sure the motor is well retained when applying the power from the battery as it will jump? and may get away from you.

If the comm is meesd up a little bit, it can be trued with a lathe and then have the mica under cut if needed. If the comm is really trashed, cutting tooo much off will result in the comm overheating or other problems.

You can test with an ohm meter between the laminations, shaft, and the comm, it won't be as good as a meggar, but if it shows ground, you have a problem.

Mike