Need Help!- 751 alarm AL-12 FANUC 18-M

[PICMAN]

HELLO,
I HAVE THIS ALARM WHEN I RUN MY SPINDLE.... THE SPINDLE SOUNDS LIKE IT HAS AN ELECTRICAL PROBLEM. (MAYBE A LOSS OF FEEDBACK) AFTER ABOUT 30 SECONDS IT GIVES ME THIS ALARM. I THINK I HAVE EITHER AN ENCODER PROBLEM OR SOMETHING IS SHORTING TO GROUND? AFTER IT GIVES THE ALARM, MY SPINDLE SLOWLY COMES TO A STOP..... IF ANYONE HAS ANY IDEAS TO HELP ME OUT, I WOULD GREATLY APPRECIATE IT.
PICMAN
P.S. MY LOAD METER STAYS AT ABOUT 25% AS THE SPINDLE IS RUNNING AND MAKING THAT SOUND.

[fanucman]

Originally Posted by PICMAN HELLO, I HAVE THIS ALARM WHEN I RUN MY SPINDLE.... THE SPINDLE SOUNDS LIKE IT HAS AN ELECTRICAL PROBLEM. (MAYBE A LOSS OF FEEDBACK) AFTER ABOUT 30 SECONDS IT GIVES ME THIS ALARM. I THINK I HAVE EITHER AN ENCODER PROBLEM OR SOMETHING IS SHORTING TO GROUND? AFTER IT GIVES THE ALARM, MY SPINDLE SLOWLY COMES TO A STOP..... IF ANYONE HAS ANY IDEAS TO HELP ME OUT, I WOULD GREATLY APPRECIATE IT. PICMAN P.S. MY LOAD METER STAYS AT ABOUT 25% AS THE SPINDLE IS RUNNING AND MAKING THAT SOUND.

easy... remove the spindle motor cables from bottom of drive.. and use a megger to test each lead to ground.. it needs to be above 100 mega ohms...
also test in between each phase to make sure you get something close to a short .3 or 3 ohms.. needs to be balanced!!

second give the machine a M03 s500 command with cables still off, if you get the alarm again.. if spindle drive is good you should get an alarm 2 or 31.. if you do get the 12 again the amplifier is damaged.. call fanuc to get a procedure to check it

third if you can get it running give the spindle motor a maximum rpm and pull off the encoder cable CN2 from bottom of the board on the drive.. this will test to see if the noise you are hearing is electrical or mechanical..

[WGoyer]

Alarm 12's are not to be trifled with. I suggest being very careful testing with the power on until you resolve this. The fact that it still runs means that you have probably not damaged the $500 transistor module(s) yet. My experience with these over the last 15 or so years is that either something external is shorted (usually wire in a flexible cable track), or something on the main circuit board is not switching the phases on and off properly.
If, after carefully checking the motor wiring and finding nothing, I would be tempted to run some external wiring. If this doesn't resolve it, I would send the board somewhere to be tested before damaging the power modules.

Warren
www.uptimecorp.com

[CHAD LAWSON]

I would agree with first using a megger meter on the spindle motor. And you should know that if you do get a reading of around 100 megohm you need to monitor it closely of the coming years as they should be 500 megohm when tested at 500volt. But they will run clear down to around ten occasianaly. As for watching the phasing or polarity that the drive is swithing phases i have found that a good fluke phasor will show you the phasing and you can see the phases toggling. There are also a few other things that you left out such as is there a seperate detector or contactor. I have found often a contactor which coil runs through the door switch on many machines will have one phase welded in place or not contacting. Also note that you can not always take the wires off of drive and meg if there is any contactor after the drive it must be done there. If your readings are bad isolate the motor from the leads and check again. The book says check parameters but i assumed this was a running machine and no one changed any otherwise check spindle parameters with manufacturers data sheets.