Emergency Alarm Related to M5

[Crashmaster]

Came into work this morning and started up my Wasino Lathe. Ran my program 20-25 times just fine. This last time I ran it, the program came to an M5 (spindle stop) at the end of my program and the spindle kept turning. It slowly lost momentum and at about 500 rpm I got hit with an emergency alarm. It seems to me that whatever stops the spindle is no longer working properly but I dont know how to properly diagnose/repair the problem. Any help would be appreciated.

[Al_The_Man]

Does the spindle drive show any LED astatus displays?
It sounds like it may be a spindle fault, something that internally shut the drive off and it coasted to a stop.
If it had been a legit SP stop from the control, it most likely would have been a controlled stop. Although an E-stop could cause the same Coast stop.
What control is on the lathe and does the screen show any alarm.
Al.

[Crashmaster]

Spindle drive doesn't show anything odd. I am getting no alarm messages either.
When I start the spindle in MDI and its below about 700 rpm it stops fine but if its higher that that and I stop it, it makes a low rumbling and grinding noise and coasts to a stop. It has a Fanuc 10T control.

[Al_The_Man]

Do you know which make spindle drive you have? Is it a Fanuc with two 7-segement LED displays?
If so are they showing normal?
Does it sound like a mechanical rumble? If so, a stethoscope probe is usefull to pinpoint mech problems, if you run it at low speed.
Also turn the spindle over manually with the belts and listen for rough spots.
It is very unusuall not to get some kind of alarm if the drive shuts down/off.
Another problem on 10 series DC spindles, were the brushes, especially tach brushes.
Al.

[Crashmaster]

Al, you will have to forgive me if I show my ignorance here. I do have 7 Solenoid valves on the side of my Lathe with LED lights. 2 of the lights are out but I dont know their function. They are labeled SOL 92 and SOL 95 if that helps. I think I need to define exactly what I was hearing. The lathe sounds good when the spindle is spinning, but when it stops it sounds like what a car would when the brake pads are going bad on it. When we manually turn the belts everything sounds fine. We checked the lubrication and all of that seems normal.

[Al_The_Man]

Like I mentioned the 10 can have various flavors of Sp drives, the Fanuc drive of that era had a couple of 7 segment displays like http://en.wikipedia.org/wiki/Seven-segment_display
They display a status number when powered which shows in run or fault.
It sounds almost like the dynamic braking has a problem, But if you just get an E-stop on M5 and no screen alarm, I would expect to at least see one on the LED drive display.
Other makes have small single LED status light such as Siemens drives etc.
Al.

[Crashmaster]

Sorry, we have just a single LED status light. And I don't necessarily think the m5 caused the alarm. It was just the act of the spindle coming to a stop from 2500 rpms. If I run the spindle that high in MDI and hit the stop button, the same Emergency stop happens.

[Al_The_Man]

The M5 and the controlled spindle stop by PB is virtually the same command to the SP Drive.
Is it the same in all gears?
The other thing I would do is disconnect the spindle motor if possible by removing the drive belts, if it has them, and see the results.
If it makes the same kind of noise, then it points to electrical problem, brushes included.
It almost sounds like the symptom of too fast braking causing too high a regen voltage, if so it could also be the braking resistors/circuit is the problem.
Al.

[Crashmaster]

OK, I will give those a try. Thanks for the input.