HELP! Fanuc 3m slow CW Spindle problem

[SSMrob]

Ok, here is the deal.. Kitamura Mycenter 1, 3m control, from around 1985 or so...

Been fighting this problem for quite some time.. Got a bit of relief, thought it still won't run at 10k rpms CW.

HOWEVER!

It WILL run 10k rpm NO PROBLEM in CCW direction! I think the bad CW/good CCW may be key to troubleshooting this issue...

Any ideas?

I am thinking now that it may be a spindle controller issue rather than brushes or anything else..

HELP ME OUT IF YOU CAN!

Thanks in advance!!!

[hrh]

What speed can the spindle reach in CW direction?
Please indicate the specification number of the spindle drive. FANUC or other?
If the spindle can run in CW, is there an alarm when the spindle reaches a speed close to 10k rpm?

[HuFlungDung]

my WAG: if the spindle drive requires a +/- 10v signal to reach max rpm in either rotation, perhaps the voltage is inadequate in one direction. I don't know if that means the power supply for that circuit is perhaps failing, or whether there would be reason for a resistance to have entered that circuit.

There may also be parameters in the spindle drive that would or could be used to fine tune the drive in an attempt to match the signal voltage to the exact motor rpm. If the motor runs open loop (no feedback), it is possible that someone may have fussed with this parameter to try to get full rpm out of the drive at +/-10v.

[GPena]

I think this is a spindle drive problem, you can check the velocity command getting into the spindle to control the speed (+/- 10V at max. speed) if it is present in both CW and CCW then you cna be sure that the drive is bad. Or you can send for revision/repair to some local company that can handle this spindle drive.

GP.

[SSMrob]

Originally Posted by hrh What speed can the spindle reach in CW direction? Please indicate the specification number of the spindle drive. FANUC or other? If the spindle can run in CW, is there an alarm when the spindle reaches a speed close to 10k rpm?

IN CW, it can reach 4k only after being warmed up for about 30mins...

If I try to increase the speed anymore than that, the load meter on the panel shoots up to max and the drive makes a stacatto sound rather than the smooth normal running sound..

Its a Fanuc spindle drive.

In CW, no alarm, the load meter just swings wildly.

[SSMrob]

Originally Posted by HuFlungDung my WAG: if the spindle drive requires a +/- 10v signal to reach max rpm in either rotation, perhaps the voltage is inadequate in one direction. I don't know if that means the power supply for that circuit is perhaps failing, or whether there would be reason for a resistance to have entered that circuit. There may also be parameters in the spindle drive that would or could be used to fine tune the drive in an attempt to match the signal voltage to the exact motor rpm. If the motor runs open loop (no feedback), it is possible that someone may have fussed with this parameter to try to get full rpm out of the drive at +/-10v.

I don't think the tachogenerator acts differently based on direction? I can't see how offhand based on the circuit itself.. Which is why I was stumped.

The spindle drive parameters are my first culprit. I know some have had them scramble due to voltage surges, welders, lightning, etc..I will double check that because I believe that the parameters can be set for CW seperately from CCW on the spindle drive..

[SSMrob]

Originally Posted by GPena I think this is a spindle drive problem, you can check the velocity command getting into the spindle to control the speed (+/- 10V at max. speed) if it is present in both CW and CCW then you cna be sure that the drive is bad. Or you can send for revision/repair to some local company that can handle this spindle drive. GP.

Yep, I am with you here.. As far as revision/repair, bah, I will fix it myself. I can fix electrical hardware without too much trouble. I did it for many years before all EE work was outsourced. I paid alot of money for my Elec. Tech degree and the few years of BSEE, I might as well use it.

[Al_The_Man]

I agree with others, check the analogue signal and see what it is doing.
I did have very similar symptoms on 6 spindle a few months ago, I did not really suspect the Tach as the symptoms were different in either direction, the tach looked fine on examination.
The final cure turned out to be a new tach.
Another was a loose helical coupling to the tach, it happened to be tighter in one direction.
Another test to distinguish between drive and motor problem would be to reverse both the armature leads and the tach to see if the problem stays with direction or not.
Al.

[SSMrob]

Originally Posted by Al_The_Man I agree with others, check the analogue signal and see what it is doing. I did have very similar symptoms on 6 spindle a few months ago, I did not really suspect the Tach as the symptoms were different in either direction, the tach looked fine on examination. The final cure turned out to be a new tach. Another was a loose helical coupling to the tach, it happened to be tighter in one direction. Another test to distinguish between drive and motor problem would be to reverse both the armature leads and the tach to see if the problem stays with direction or not. Al.

Now, here is where I am lost.. WHERE is the tach?!? I don't have a wiring diagram, so I can't be coy and make sense of it that way...

Where is this bugger buried, what do I have to rip apart to get at it?

The standard Kitamura docs are ok, but they only show basic electrical-mech stuff, not any feedbacks signals or anything like that..

[Al_The_Man]

It is the little DC motor looking thing that is usually mounted very vulnerable on the back end of the Spindle motor shaft, A Tamagawa I believe. It has a two conductor cable coming from it.
Al.

[hrh]

FANUC 3M Control 1985....

Should be AC Spindle (analog) drive A20B-0009-053_ OR A20B-1000-069_
The PCB should have LEDs in the middle of the PCB marked 8, 4, 2, 1, PIL
Please confirm this because this drive's motor does not use a tacho generator but a sine cosine pulse generator.

The old FANUC DC spindle motor has a cover with three bolts underneath which the tacho is situated. (I doubt that this is the case for your machine)
The old AC spindle motor has the pulse generator located on the rear of the motor after removal of the cooling fan cowling.

[SSMrob]

Hey man, it ended up being the Spindle encoder. Be prepared to spend $300.. Its not cheap.. Ow.

It works well now, no issues..