Seimens Spindle Erratic

1990 Tornos lathe

Maybe a 5hp motor?

Slowly git'n worse, and soon to be beyond useability I'm guessin'.

It just aint smooth. It is very rough.

I liken it to the time that I had the rubber star/bushing in a small Lovejoy type fitting come out (disintegrate?) on a 40hp DC motor, and it was erratic to the point of making the RPC on the other end of the shop dance the jigg!

The spindle does have a belt driven Heidenhain encoder on it - but I think that it is likely only used for C axis.
That encoder does need replaced as the HOME pulse is bad, but if I run it in INCR, it is fine, so ...

But I am guessing that there is a tach up inside the spindle motor.

It seems to warm up and then work better, but ....

From anyone's experience here, what is more likely the problem?
The tach being bad?
Or the amp getting bad?



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Think Snow Eh!
Ox

if you didn't say you had issues with the encoder I would point right at the drive. I'm assuming it's a 611a? 95% of all my problems on my old emco465 were power sections on those drives. mine also had the hh belted to the spindle and for almost 20years game me no problems.

This is the unit:


Have you been able to fix it yourself?
Send it out?
Buy new?


I have a newer Siemens power supply that is having trouble swallowing re-gen.
It'll spin it ratt on up, but shutting it down at anything north of 1500 - it trips out.

I had my tech replaced whatever caps that he thought would be assossiated with this, but it came back exactly the same.
Not sure how bad I want to invest trying to fix it ourselves unless someone else has had good luck.

But more concerning yet - is if you have had several bouts of this, then it may not be a good gamble to buy used off e-bay?


???


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Think Snow Eh!
Ox

Actually - the only one on Ebay from North America, is about 45 minutes from me, and he is offering 30 day return, so - maybe I should give that a shot?


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Think Snow Eh!
Ox

I sent everything to Siemens for repair. Had a third party quote me more than what Siemens wanted.

Picked up that newsed drive - which happened to be out my back door - and now she runs smooooth again!


I guess I haven't tried the C axis on it yet, but - at least all looks well for now.



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Think Snow Eh!
Ox