Need Help!- Fanuc 0M, intermittent AL-42 on spindle drive

[1000ee-monarch]

I'm starting to get frustrated with this problem.... want to see if anyone here has any ideas. Pardon the long post however there are a lot of details.

Machines are two Kitamura Mycenter 0's, 1993, Fanuc 0-Mate-MC, 2S spindle drive, machines are identical, consecutive serial #'s, and have the same exact symptoms.

Both machines worked fine here in CA. Got shipped across the country to MA and now have a problem orienting. 1 out of 5 to 20 attempts to orient (M19 or during toolchange) causes an AL-42 on the spindle drive. The rest of the time it works fine. After getting the AL-42 power gets cycled to clear the alarms.

Spindle drive maintenance manual describes AL-42 as " position coder 1-rotation signal not detected".

Here's the details on the machine configuration:

There is a magnetic orientation sensor on the spindle, part # A57L-0001-0037. It's the common one used on machines that vintage that uses the pre-amplifier box. There is also a position sensor on the top of the motor that is used for rigid tapping. The motor is connected to the spindle by timing belt. The two sensors are connected to the spindle drive "detect board" part #A16B-1300-0220, ver. 02A. That is NOT the older board with the row of adjustment pot's.

The spindle drive is a serial 2S, drive part # A06B-6064-H302#550. Rom 9A50.

Magnetic sensor and pre-amp. have been swapped, same thing. Magnet on spindle has not been swapped yet.
All cables were examined, yanked on/wiggled, etc. Cables appear good.
Fanuc has checked signals at the test points on the drive and say all looks good. Therefore, magnet, and sensor are good (correct??).
All the spindle drive boards have been swapped except for the "detect board". That is being swapped today.
Parameter 6578 (MS signal constant) and 6579 (MS signal gain) have been "tinkered" with and do not seem to have any effect on frequency of problem.

Spindle runs fine, not other alarms at all.

Machines rigid tap fine. I'm pretty sure that the position sensor on the motor does not have a one per rev. (index) signal. Machine does not orient prior to rigid tapping as a matter of fact if one were to rigid tap the same hole twice it will cross-thread.

I'm in CA and am trying to troubleshoot this remotely by hiring different tech's in MA (including Fanuc). About 20 hours total so far and counting by 3 different people and no diagnosis yet!

It has been observed that when the alarm occurs the spindle has rotated much less than one turn and the magnet has not passed in front of the sensor even once.

Oh, and power both here and in MA is 208 Y. Have tried disconnecting ground and letting machine float. People have checked voltage leg-to-leg and leg to ground with meter and scope. Nothing interesting or unusual has been found. Regular ole 208 Y.

Anyone know of a way to change the software (ROM) to disable the occurance of the AL-42? I'm getting desparate here.

I have a feeling that the machines will run just fine if the AL-42 is not triggered. Disconnecting the magnetic sensor from the pre-amp. and orienting the spindle just spins and spins and no alarm.

OK thanks for reading this long post (if you read it that is, haha), and I appreciate any ideas.

[1000ee-monarch]

Update: "detect board" was just swapped. No luck, same thing....

[tc429]

any chance when they tarped/shipped the machines they might have done some damage to the cable track? just odd both did it after moving...does it do it more often if m19 with spindle running already vs m19 from stop? maybe the programs are different than what it used to run...

[1000ee-monarch]

We think we have a solution.

Parameter 6507 bit 6. If set to a 1 it disables the AL-42. Tried that and both machines orient fine and appear to run fine.

Of course this doesn't explain why both of them worked fine here and started having this problem all of a sudden, but heck if this makes them work then who really cares? This might go down as one of those mysteries that's never fully understood.

Another interesting observation was made. If the spindle rotates in reverse (M4) prior to orienting it worked fine. I was about to add a macro to run the spindle backwards bore toolchanging!

And yes we looked at cables very early in this and don't see any damage. The cables on these little Mycenter-0's are very exposed and easy to follow.