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Fanuc OT-c 'not ready' during cut

gregormarwick

Diamond
Joined
Feb 7, 2007
Location
Aberdeen, UK
One of our lathes has developed a problem that's driving me crazy.

It's roughing down large billets and working hard, 100% spindle load etc..

Shortly after entering the cut it stops dead, control power off, with 'Not Ready' flashing at the bottom of the screen. There are no alarms whatsoever, just the not ready. No alarms on the drives either, just the same "--" not ready.

I can press control power on, zero return, and restart like nothing had happened.

I am getting really tired of breaking tips when it stops dead in the cut, and of having to restart the program constantly.

Anybody have an idea what's wrong with it?

Thanks in advance, Gregor
 
Update: After having done about a dozen passes without a hiccup it's now alarming out in about the same spot (just after it enters the cut) with a Z+ overtravel alarm. It's feeding in the Z- direction when it does this...
 
It could be a fail safe.
Try lowering your spindle load to 80% or so.
Do you have a Z axis load meter ?

Usually on our cnc lathes , when OD roughing , the Z axis load meter can get high.
Its possible your axis is being over powered.
Machine shuts down to save itself from damage.

Lower your DOC (depth of cut) a little bit... That will reduce Spindle and Axis load at the same time.

Good luck
 
Gregor, what about broken / chafed wiring to the limit switch on Z. If you can run it without a job in, nip round the back and flex the cabling to the switch and see if it shuts down.
 
Sounds as though either the spindle drive or axis drive is faulting."Not ready" means the control is not seeing the ready signal from either of these.
Be inclined to go for the spindle drive myself.Try easing of on the spindle load and see if your problem goes away,also get someone to check the supply voltage to the drive while in cycle.
 
It could be a fail safe.
Try lowering your spindle load to 80% or so.
Do you have a Z axis load meter ?

Usually on our cnc lathes , when OD roughing , the Z axis load meter can get high.
Its possible your axis is being over powered.
Machine shuts down to save itself from damage.

Lower your DOC (depth of cut) a little bit... That will reduce Spindle and Axis load at the same time.

Good luck

No, it doesn't have a load meter for the axis, but I'm not inclined to think it's anything like that. Should get a soft-thermal alarm in that case, also on the servo tuning page you can see it's rarely going over 50% current.

Gregor, what about broken / chafed wiring to the limit switch on Z. If you can run it without a job in, nip round the back and flex the cabling to the switch and see if it shuts down.

The alarm (520) is a soft overtravel, not related to any limit switch. But I tried just in case - no joy!

Sounds as though either the spindle drive or axis drive is faulting."Not ready" means the control is not seeing the ready signal from either of these.
Be inclined to go for the spindle drive myself.Try easing of on the spindle load and see if your problem goes away,also get someone to check the supply voltage to the drive while in cycle.

That was my first thought too, and the machine does have an intermittent problem with the spindle motor encoder but it always throws an alarm with that.

Anyway, I've shut the machine down for now and got a tech coming on monday to replace the spindle motor encoder and see what else he finds.

Thanks for the replies, Gregor
 
I'm sure you have thought of this, but figured i would mention anyway. I was getting the same thing the last couple days on occasion during a cut, then today spindle would try to start and stop with the "Not ready"(No alarm, Couldn't get it to start at all). I thought it might be the drive, but i have narrowed it down the the hydraulic collet chuck.
 








 
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