Need Help!- Partner VI growl noise in Y rapid

[RJ40]

I'm a newbie here but I've been at this a long time. But i need help with a 95 Partner 6 please. I've tried searching the site but find no referance to this. I just finished an extensive rebuilding of this vertical machine that included new ballscrews, thrust bearings,linear rails and bearings,and belts and pullies. Everything works great except the Y axis has noise. It sounds like a growl or rumble at anything over about 15 in/min. and can be felt as a vibration thru full Y travel. It can also be seen in the finish when side milling. With the ball screw nut un hooked from the table the table glides very smoothly by hand. And the ballscrew turns smoothly by hand. When hooked up the faster you feed or rapid the table the more noticeable it is.
I don't know if its possible ,but it almost seems like the pulses to the servo motor are to agressive? Or is the servo motor or encoder just bad ?
I hope you guys can help
thanks RJ

[franchcnc]

Do you know which servo motors this has? I assume 95 partner 6 should have SEM DC motors. If that is the case try cleaning the tach dust out of the motor.

[RJ40]

I just came from working on it. Can't make out the name on the tag. All the color part has long ago melted. The stamped numbers are there though. The owners manual doesn't mention the brand ,but does designate tach wires so it does have a tach in it.
Just to cover the bases I swapped the -x- & -Y- drive cards. No change. Then ran it both ways with the belt off (no load).A different sound and a lot quieter but it just didn't sound right. and was different in forward and rev. Via a stethascope it is noisier and different than the -X- especially inside the cover at the back.Turning by hand the bearings seem fine.
So tomorrow I'll pull it and get under the cover.
Thanks for getting back . That gives me a direction. Any secrets to getting to the tach for cleaning?
Rick

[Anthony Dimock]

I have same problem with a milltronics. I cleaned tach best as I knew how and still doing it. Im not sure what to do next.

[RJ40]

My tach was splattered full of dust. I cleaned it out and dressed the armature smooth. now the ball screw turns very slowly on start up before ever homing ? If I try to home in this condition it rapids toward switches but faults out and e-stops. The good news is the noise is gone.
So any suggestions what to adjust next ?
Thanks
Rick

[HuFlungDung]

Are the tach brushes seated properly? Are they worn too short perhaps? What you described sounds like runaway from no feedback, so it sounds like a bad connection possibly from anything associated with the tach.

[RJ40]

Thanks for quick response HuFlung,
The commutator and brushes looked like new when I put it together.
I did block sand tips of brushes with 600 emery. They are plenty long and look very good. How would I go about getting them to seat properly ?
I too was thinking it seems to be not getting a tach signal. So I was thinking I may have broken a wire on assembly. I did notice that the following error that used to be +.0025 and flickering is now -.0007 and steady ?
I'd appriciate any other notions. I'm gonna try to meter those wires today.
Thanks

[HuFlungDung]

It is not recommended to apply hard abrasives to the brushes as they could embed and lead to scoring of the commutator. The usual method of seating brushes is with a special soft brush seating stone.....I'm not sure where to get these but a motor rewinder could tell you. The only problem is that the commutator has to be turning at a good clip, the stone is held against the comm and it rapidly wears in the brush tips. On something as delicate as a tach, I suppose special care is required.

Check for broken connections, or bad solder joints, as that is more likely the problem if the brushes are like new yet.

[Al_The_Man]

With these servo amps that have a inner loop, tach to drive, as well as the outer loop, encoder to controller, I have found the best way is with a 9v battery box using a 5k pot applied to the drive analogue input signals.
This tests the drive, motor and tach without the controller in the picture.
You could also remove the analogue input and connect a jumper across the analogue input terminals, the motor should not turn or at least very slowly, now you can tune the drive
If it drifts excessively or it runs away, and you have eliminated the drive, then it is the tach?
Al.

[RJ40]

Al,
I have only limited knowledge on electronics . I appriciate your input but i just don't know where to find the analogue input or how to tune the drive. If you can explain in more detail and specifics I'll sure try. I have good meters and a variable dc power supply to 90 V and basic machine wiring diagrams.
Today I disconnected "X" tach wires at the junction block in cabinet and metered them for ohms and a referance of what a proper servo should read. Next same with problem "Y". X reads 35 ohms. "Y" at 25 . So I guess
the wires aren't broken but that's still a 28% diff. Looking more like seating brushes is the thing to do.
If I remove the belt ,disconnect the tach wires, disconnect the motor wires from junction block and connect motor to a remote power supply and let it run a while will that seat brushes? What voltage should I run? The encoder would still be hooked up. Will that hurt?
Thanks
Rick

[ZZZZ]

Did you maybe reverse the tach leads while you had it apart?
That will cause the run-aways.

[RJ40]

I'm sure not because I never disconnected any wires under the cap.
But thanks. Believe me I appriciate any input.