Z-axis Motor Rebuild

[starone]

Need some insight. We have a Mori-Seiki SL-2 that has been throwing a "401 Servo" alarm whenever we jog in Z. We had a tech come out and take a look, and he said the Z-axis motor needs a rebuild. Unfortunately, it's not work he can do, so we have to sub it out to someone else.

Is there anything that we need to know before we remove the motor? Any potential alignment issues we need to be aware of? Any insight is much appreciated.

[Al_The_Man]

If its the older Fanuc/Getty's DC motor there is not alot to it, the ones I have removed had terminals instead of MS connectors which is a bit of a pain.
It is often caused by a carbon build up on the bottom of the brush cage or brushes worn right down.
Al.

[starone]

Al, thanks for the quick reply. I think you're right; it looks pretty straight-forward. We just wanted to check with some folks who have more experience than we do.

[Al_The_Man]

I forgot to mention there is no coupling etc to disconnect as they are normally gear drive, so the motor lifts out with the gear on the shaft.
Al.

[underthetire]

And watch out for motor shops. A lot of them are not used to working on servo motors. I've had quite a few not work come back from "re-builders". Is the motor shorted? Bearing failure? Magnets come loose? all makes a difference where you send it. The service guy should have told you what he thinks the problem is with the motor.

[Al_The_Man]

While it is out, check the brushes on the X, Helwig Carbon sell sets.
Cheap insurance.
Al.

[claya]

While it is out, check the brushes on the X, Helwig Carbon sell sets.
Cheap insurance.
Al.

I just posted a thread about Helwig Carbon & brushes. Do you know if there is a cross reference part number for Yaskawa brushes? They quoted me a custom brush, based on brush dimensions I supplied. Like to know if there is a specific cross.

[Al_The_Man]

I don't know of one, You could scan through their catalogue and see if one compares?
Al.

[cncserveng]

alarm 401 indicates velocity control signal is turned off. it couod be any axis feedback, tach, voltage...you could look at diagnostics 700 (or maybe 500).
diagnostics 721 = #1 AXIS, 722=#2 AXIS, 723=#3, THE DISPLAY HAS EIGHT BITS. Check in the Fanuc maintenance manual.

example;

starting at the extreme right is bit 0, then bit 1, then bit2 then bit3,

then bit4, then bit 5, then bit 6, and finally bit 7.....

7=0vl=an overload alarm

6=lv=a wire shorted or low excitation to the encoder

5=0vc= excessive current alarm

4=hcal= improper current alarm

3=hval= an overvoltage alarm

2=dcal=regenerative discharge alarm

1=fbal=a wire disconnection..feedback loss.

0=ofal=an overflow alarm

With power off, check and clean the brushes, make sure the commutator is clean without a deep groove. Vacuum out the motor of all brush dust if you can or lightly blow it out with all the brushes removed. do not breathe in the dust it is quite nasty stuff. Can you turn the ballscrew by hand ? is the axis tight ? etc;