Newbie- ac/servo overheat

[aaiusa]

I have a fanuc series 15 and my z-axis servo is getting hot even when not in use (when in idle machine on) The other Axis servos are cool to the touch. Is this normal and if not what could be the problem?This is a Shoda cnc Router With Mitsubishi plc contollers.We had to change one of the servo contollers about 2 years ago with a rebuilt one.

[Al_The_Man]

Usually means there is resistance even at rest and the motor is either underpowered or there is mechanical friction, in the case of a Z axis on a mill, usually often the counterbalance is not working or ineffective, depending on the method you have.
Al.

[gbowne1]

I would use the servo tuning if you could. Maybe it's getting out of tune.

Yeah its quite possible to have an innefective counterbalance.

[aaiusa]

Originally Posted by Al_The_Man Usually means there is resistance even at rest and the motor is either underpowered or there is mechanical friction, in the case of a Z axis on a mill, usually often the counterbalance is not working or ineffective, depending on the method you have. Al.

I have a pnumatic counter balence system and all are working properly. I just pulled the servo and found a bad bearing in the motor. I hope this is my problem. the winding are showing signs of over heating. I am in the process of having the servo rebuilt and hopefully this will fix it. Thank you for your help and this is a great site.

[gbowne1]

Overheating? yeah thats possible with a bad bearing. It's possible that the servo got stressed at some point in its life.

Part of my regular maintenance is to check servos. Make sure that they are not getting damaged.

I also make sure that everything is moving as it should and not overload or overheat the motor.

What type motor is it? Mine was rebuilt twice and the 2nd time it was certified. Mine is a FANUC 3S. I also have the 6S and 8S types to that I could use if I wanted. They're so expensive that I bought two.

[aaiusa]

Originally Posted by gbowne1 Overheating? yeah thats possible with a bad bearing. It's possible that the servo got stressed at some point in its life. Part of my regular maintenance is to check servos. Make sure that they are not getting damaged. I also make sure that everything is moving as it should and not overload or overheat the motor. What type motor is it? Mine was rebuilt twice and the 2nd time it was certified. Mine is a FANUC 3S. I also have the 6S and 8S types to that I could use if I wanted. They're so expensive that I bought two.

Fanuc 20S. I believe this is the first time since we've had this machine to replace a servo. We have had this machine for 15 years. Not bad for all the work it has done.

[gbowne1]

Yeah, it's great to have a machine last at least a decade without major failure.

The 20S is a good spindle servo motor.

The 3S and 6S seems to be the most popular of the S spindle servos. I never see to many of the others.

I just don't have the greatest information on them.

[aaiusa]

I changed servo and it helped. The servo is not heating up as quickly but is still getting warm during idle time. I',m wondering if my pnumatic balencer is not set right. When I power down the Z-Axis travels up and I'm thinking it should not move at all, down or up. Is it trying to push against the balancer when in idle and that is what is overworking the servo?

[Al_The_Man]

If the counterbalance is still active as when the servo is powered then it is pointing to wrong adjustment, ideally there should be virtually no back feeding when the motor is inactive.
Al.

[aaiusa]

Originally Posted by Al_The_Man If the counterbalance is still active as when the servo is powered then it is pointing to wrong adjustment, ideally there should be virtually no back feeding when the motor is inactive. Al.

I adjusted air to counterbalance. It is working properly now thanks for all your help. This is a great site.