Anyone replaced the bearings in the original steppers?

[badgs750]

I have a Series 1 with the old finned steppers. The fins run parallel to the shaft, I think that helps with identifing the brand. Anyway, I am getting ready to do an upgrade to the controller. I took the motors off and noticed that one of the motors has a funny noise while turning the shaft by hand. If I pull on the shaft while turning it and the noise goes away. So, I am thinking that it is one of the bearings. Can anyone give me advice on replacing the bearings in this motor, things to watch out for?

Thanks,
Todd

[unterhaus]

I believe you need a keeper to successfully pull the rotor. I have ruined stepper motors by taking them apart. They get very weak. Just a note for your consideration. I don't know if what you are feeling could simply be fixed by adding preload.

[HillBilly]

Somebody posted that you could use a TV deguassing coil on the stepper after disassemble and restore it. I do not know the validity of that.

You can replace the steppers with equivilents. I would not advise going above 8 amps. I have a NC2A drive cabinet (same drives as BOSS3-6) I am running different motors on.

Darek

[NC Cams]

Any time a PM motor is disassembled, you "break" the magnetic field and it is reduced somewhat.

This is why PMDC motors often have the magnets "charged" AFTER the motor is assembled. To chage the magnet, they usually fire a highly charged and oriented magnetic field THRU the motor.

A degausing coil DEMAGNETIZES the TV screen - hardly what you want around a PMDC motor of ANY kind.

Might help to do a "motor remagnetize" search on Google for more info. The RC car and slot racing car guys did a LOT of work with PMDC motor remagetizing.

It is NOT something to mess with as LOTS of power is thrown at the magnetizing coils in a very short time from highly charged capacitors - ugly stuff happens it you got zapped instead of the magnet...

[badgs750]

That is one of the things I was wondering about. My neighbor was over last night and said he thought that it may loose its charge if taken apart. He wasn't sure though. I just wanted to replace the bearings, thinking that is where the noise is coming from. I think that the best way to go is to try and replace the one bearing on the end plate that comes off and just run it.

I would like to buy servo motors to replace them, but have not found a good source for replacements, for a good price.

thanks for everyone's advice,
Todd

[HillBilly]

http://www.cnczone.com/forums/showthread.php?t=3848

Here is the thread.

I wondered about it. I have seen speaker magnets energized in a strong DC magnetic field. A degaussing coil hooked to a AC outlet spells de-magnitize, as you stated.

Darek

[AlanD]

My advise is that if you can't replace the bearings without removing the rotor then DON't (even doing this may NOT give you the resluts you seek so, live with the noise till you get a suitable replacement motor).

According to my understanding, even taking the ends off a stepping motor may compromise the magnetisation (spoil its performance) and even with carefull marking of the allignement of the ends etc. it is a very difficult job and probably only reliably done in the factories where de-magnetising repair and re-magnetising would be readily done.

Originally Posted by badgs750 I have a Series 1 with the old finned steppers. The fins run parallel to the shaft, I think that helps with identifing the brand. Anyway, I am getting ready to do an upgrade to the controller. I took the motors off and noticed that one of the motors has a funny noise while turning the shaft by hand. If I pull on the shaft while turning it and the noise goes away. So, I am thinking that it is one of the bearings. Can anyone give me advice on replacing the bearings in this motor, things to watch out for? Thanks, Todd

[AlanD]

It just occurred to me that ther may be 'professionals' other than the OEM makers:

http://acsindustrial.com/stepper-motor-repair.php

No doubt there are more?

Originally Posted by badgs750 I have a Series 1 with the old finned steppers. The fins run parallel to the shaft, I think that helps with identifing the brand. Anyway, I am getting ready to do an upgrade to the controller. I took the motors off and noticed that one of the motors has a funny noise while turning the shaft by hand. If I pull on the shaft while turning it and the noise goes away. So, I am thinking that it is one of the bearings. Can anyone give me advice on replacing the bearings in this motor, things to watch out for? Thanks, Todd

[badgs750]

Before I knew anything about the lossing its magnetism, I already had the cover off on the shaft side. That side had the bearing dust seal loose, so I decided to just replace that bearing. I will run it and hope for the best and watch for a backup motor. Thanks for all the help and I will hang on to that link to the stepper motor repair place.

Thanks,
Todd

[AlanD]

Hello Todd - I should have warned you that the running clearances between stator and rotor are minimal (sometimes down to 1/1000") so removing & re-fitting the end-plate-bearing assembly needs to be done such that an even running clearance is preserved.

The magnetic attraction between the rotor and stator creates an un-stable clearance. In my limited experience, a little 'strategic' tapping with a soft face hammer during progressive tightening of the thru-screws is needed. Under NO circumstances use a metal hammer - the harsh shock will be likely to 'destroy' (weaken) the magnetism in the rotor.

I have an underlying concern that even the disturbence of the end bearing support-housing may compromise the motor's magnetics because of the 'nature' of the magnetic properties achieved under final magnetisation in the factories. Just how one can deploy a 'keeper' and still replace the bearings I do not know - presumably someone will reveal this for our benefit one day?

Good luck and PLEASE report on your experience for the benefit of others.

Originally Posted by badgs750 Before I knew anything about the lossing its magnetism, I already had the cover off on the shaft side. That side had the bearing dust seal loose, so I decided to just replace that bearing. I will run it and hope for the best and watch for a backup motor. Thanks for all the help and I will hang on to that link to the stepper motor repair place. Thanks, Todd