'2D' alarm on Mitsubishi 50M control - anyone know?

[SRT Mike]

Well this isnt my month - in the middle of fixing my lathe, the VMC (Leadwell V-40 with Mitsu 50M control) starts giving alarms.

The alarm is gives is 2D, which isnt in the manual but from the servo driver documentation from Mitsu it says "detector internal data error".

I thought my X thrust bearings had turned to mush because the table made a hell of a grinding noise sometimes moving in X, but the noise seemed to happen at different parts of the table. Upon pulling the way covers, everything looked fine, but I discovered what was really happenning was it wasnt grinding, but rather at some points the ballscrew was twitching back and forth and it was the whole table basically vibrating/moving back and forth about 1/2mm trying to find a position.

Sometimes it errors right away, sometimes it doesnt. It seems to happen less if turn on the machine and let it warm up.

It has to be a bad servo drive, bad cable, or bad encoder. I am leaning towards the encoder, because it may be my imagination but it seems to happen at a certain point of rotation of the ballscrew.

But I figured I'd ask if anyone else has had this problem before and if so what was the solution? Mitsu in the servo driver manual says the encoder (detector as they call it) is "non serviceable and should not be removed from the servo". No way am I buying a whole servo if it's just a bad encoder, but provided I got the same part num. encoder, it should be a drop-in replacement right? Or is the encoder position linked with some special motor shaft orientation at the factory that I will screw up if I take it off?

Any further diagnostics anyone would suggest?

[SRT Mike]

Just to close out this issue in case someone comes across it in a search, it ended up being a bad encoder. I swapped the X and Y servo drives and the problem stayed on the X axis. I tested the cable and it was OK. No visible damage to the encoder but when I would take it out and clean it all off and put it back, the error would come and go.

Bought a new encoder from Mitsubishi - $506 and change. Put it in, machine is working fine and we're back to making chips.

Probably would have been $2k+ if I called the service guy after travel and all... so that $$ can go in the Xmas present pot!

Cheers
Mike

[dpelivan]

Hello Mike !

I had similar problem on my Matsuura moving Z axis.
Problem was in brushes on tacho generator on Z axis motor.
I don't know is that same problem but symptoms are the same as it was on my machine.
Also my Matsuura has Yaskawa motors and servo.

I hope that this will help you !

Best regards !

Davor Pelivanovic

Osijek, Croatia