Need Help!- Y axis over travel during zero return

[kirby]

I have a Fanuc Om controller on a Excel/Kiwa VMC. I think it is a 1991. Lately we have been having a few issues on the Y axis. There is quite a step on approach and depart. We had a part that required a finish and it seemed like it was in a different position every time it came out of an arc an into a flat. I could give mote detail on that but for now i will keep it simple and get to the problem.

Came in this morning and went to zero machine. We ended up getting a 406 and a 420 alarm. (i am hoping that those are right as i never thought to write them down). So we reset the machine and tried again. From this point onward all i get is an over travel alarm when i try to zero return.

I checked to limit switches and there doesnt seem to be anything loose or caught in them. I thought about messing with them but i figured since nothing seemed to be wrong it made no sense to create more problems till i was sure it was an issue.

Personally i think there is something more wrong here than a limit switch. There have been to many other issues with that axis in the past. I am pretty sure we actually replaced the drive on it a few years ago.


Hopefully there is someone who has an idea about this as i am at a loss...

[underthetire]

Hold down Can and P during power up, then zero the axis. As far as the other issues, need to set the backlash parameter to zero on that axis and see how much mechanical backlash is actually there. I have also seen the Box way versions of those machines loose the Turcite.

[kirby]

Originally Posted by underthetire Hold down Can and P during power up, then zero the axis. As far as the other issues, need to set the backlash parameter to zero on that axis and see how much mechanical backlash is actually there. I have also seen the Box way versions of those machines loose the Turcite.

Thanks so much...that fixed it.. Wonder what would have caused that?

As far as backlash goes i have set that. I have programs loaded into the controller to check that. Once the program runs i have the backlash out. But if i move the table by the handle after i set zero there is a bit of a repeatability issue of a thou or two.

[underthetire]

If your comping more than .002 backlash, it needs thrust bearings at minimum. Those machines also have major Lube issues, with broken lines and/or plugged up restrictors, and I have seen several with non sealing waycovers that get packed full of chips underneath. What your describing sounds like stick-slip, bearings or lack of lube can cause that, as well as the saddle pitching on the ways.

[kirby]

Originally Posted by underthetire If your comping more than .002 backlash, it needs thrust bearings at minimum. Those machines also have major Lube issues, with broken lines and/or plugged up restrictors, and I have seen several with non sealing waycovers that get packed full of chips underneath. What your describing sounds like stick-slip, bearings or lack of lube can cause that, as well as the saddle pitching on the ways.

It does likely need bearings but at this stage its not likely worth it. Just so many little issues.

Not sure if its related or not but what would cause this machine to just shut down into "not ready" mode? Sometimes in the middle of a tool change sometimes just sitting there powered up sometimes during a rapid move..Puzzles me to no end....

[underthetire]

Does it say not ready or EMG ?

[kirby]

Originally Posted by underthetire Does it say not ready or EMG ?

just shuts down and flashes "not ready"... usually just power it down and back up again....but sometimes it takes 3 or 4 times to get it...

[underthetire]

That one can be tough. You need to check the Fanuc Diagnostic page for the servo errors first, to see what bits if any are on. I don't have a O-M book here, only i series, so can't help with which ones.