[blabs]

I have a Summit Smartcut CNC Knee mill with a Fagor 8055i control. The Z axis started to ocillate up and down (like shaking) once in a while a few months ago. I turned the control off and started it up again and it went away. Now it don't go away. I went back to the manufacturer and they think maybe the scale is missaligned or dirty. Not sure that this is the issue though. I removed the front cover and the scale is sealed and looks pretty clean on the outside. All the screws are tight. When I first turn the machine on, everything seems to work, I can home the machine, but when I go to move the Z axis, it just shakes, then I get a Z overide error. I talked our maintenance person, (where I work at my full time job), and he thinks it is the brushes in the Z axis motor. I attached a few pictures of the motor nameplate, Error on the screen and the Z scale. Any suggestions would be greatly appreciated

[machinehop5]

...dirty or bad Z axis Tach Brushes most likely. Tachometers are very low voltage systems and need maintenance.....If, the Tach and Motor brushes are ok then, there are some adjustable Pots on the Amp's ....what Model Glenteck amp/driver do you have?

[blabs]

...dirty or bad Z axis Tach Brushes most likely. Tachometers are very low voltage systems and need maintenance.....If, the Tach and Motor brushes are ok then, there are some adjustable Pots on the Amp's ....what Model Glenteck amp/driver do you have?

I attached a picture of it, I think it is GLENTEK model Gm4040-41-024502510-279A. I took the brushes out, they all look about the same, 2 of them have a little carbon dust on them, but don’t look bad

[kawazuki]

I attached a picture of it, I think it is GLENTEK model Gm4040-41-024502510-279A. I took the brushes out, they all look about the same, 2 of them have a little carbon dust on them, but don’t look bad

That's the motor - the question was, what are the electronics that drive the motor!

[blabs]

That's the motor - the question was, what are the electronics that drive the motor!

Sorry for the late reply, there is a Z axis drive in the cabinet, I took a picture of it but could not attach here

[blabs]

I tried to attach the picture of my Z drive, Don't know if it attached or not

Attachment 482008

[machinehop5]

...the photo helped and looks like all 3 Servo drives are the same. Which is good thing when troubleshooting if, the problem is the Motor side or the Servo drive side.

NOTE:
There are very "HIGH VOLTAGES" used in motor drive systems and you must wait til the Capacitors have fully discharged after Service POWER OFF before servicing anything.

With that being said, the next question is how comfortable are you with swapping the drives?

[blabs]

...the photo helped and looks like all 3 Servo drives are the same. Which is good thing when troubleshooting if, the problem is the Motor side or the Servo drive side.

NOTE:
There are very "HIGH VOLTAGES" used in motor drive systems and you must wait til the Capacitors have fully discharged after Service POWER OFF before servicing anything.

With that being said, the next question is how comfortable are you with swapping the drives?

Well, I have never tried this. Not sure how they come out. Looks like a couple of screws. I am trying to work with the company I purchased from, ( new in 2012), but they are really slow at getting back to me. I really appreciate your help!

[machinehop5]

Well, I have never tried this. Not sure how they come out. Looks like a couple of screws. I am trying to work with the company I purchased from, ( new in 2012), but they are really slow at getting back to me. I really appreciate your help!

...yes, you're welcome. You said you cleaned and check the Tach brushes and lightly blew off all the carbon dust inside the motor. So, at this point we could 1st try turning down the COMP Pot (outlined in red) on the Z Drive...it should be the 3th Pot in the attached photo.Check printing on case should be marked. . Turn off Power for 15 mins (Cap Discharge) or so and Use a small screw driver to adjust 1 Turn CCW...then Power up machine to see if, it stops the oscillation.

[blabs]

...yes, you're welcome. You said you cleaned and check the Tach brushes and lightly blew off all the carbon dust inside the motor. So, at this point we could 1st try turning down the COMP Pot (outlined in red) on the Z Drive...it should be the 3th Pot in the attached photo.Check printing on case should be marked. . Turn off Power for 15 mins (Cap Discharge) or so and Use a small screw driver to adjust 1 Turn CCW...then Power up machine to see if, it stops the oscillation.

Okay thanks. Also, I started up the machine yesterday and it ran fine for about 10-15 minutes before the Z axis started acting up. I ran 2 tools through 6 parts. I will try to look at it today, but probably sometime next week. I will let you know if it works

[kawazuki]

Maybe its a heat thing ie it takes 10 - 15 minutes to warm up and overheat a component? I see a bank of fans - have you checked they are ALL working as the Z axis driver seems to be top of the pile for heat rising?

[tanumarket]

Thank You!! Nice Article..
https://www.marketreportsinsights.com/

[blabs]

Maybe its a heat thing ie it takes 10 - 15 minutes to warm up and overheat a component? I see a bank of fans - have you checked they are ALL working as the Z axis driver seems to be top of the pile for heat rising?

Yea, I think you are correct. I did turn the comp pot 1 turn CCW and it worked all day until the last set of parts. I want to thank you again for the information. I am going to remove the board and see if there is anything obvious.

Thanks

[OldSchoolProgrammer]

It may be the control and not the machine. If the position feedback gain, particularly the differential portion of the gain loop, drifted higher than the factory setting, the oscillations you describe could easily happen. One initial check for that is to position the Z axis at several arbitrarily chosen locations each several inches apart from the others. If the oscillations happen at multiple locations, that could indicate a feedback adjustment problem. You said the Z axis scale looked clean, but what about the scale reader? A dirty reader is also a possibility, and it wouldn't take much time to remove, check and clean if necessary and reinstall the reader. An iffy electrical connection anywhere in the servo loop could be a cause too, but checking the reader and the loop gain would be my first efforts because they take less time and seem to me to be more likely culprits. (Motor brushes COULD be a problem source, but I've operated, maintained ad repaired CNC machine tools and controls with thousands of hours of operating time and have never encountered an oscillation problem due to motor problems.)