Need Help!- Backlash adjustment on Oi-MC control

[MOTOXMAN]

I have a Fadal 4020FX with a Fanuc Oi-MC control put into service in January 08 and I have a backlash problem in X. I have already go the machine leveled and gibs adjusted and my backlash does not change. If I am near the left side of the table the backlash is .0007 towards the middle it gets better and over to the right I can not find any backlash. It seems to be a gradual progression. Can I do a zone backlash adjustment?

[zavateandu]

HI M8

yeah u can do some adjustment but "we" called pitch errror compensation not backlash cause backlash is a fixed value that it will affect all the lenght of u ballscrew .

the pitch error compensation is a variable adjustment depending on the wear of u ballscrew .

this adjustment of pitch error is not so easy operation only some dudes can do it but also u if u have a sharp mind.

in regular cases for this operation u need a precisely measuring device (laser measurement) but in u case is not necesary cause the wear is not so big and is only in a small area.

i will send to u the files to read and than if u understand to can talk and help u if not do not change the parameters is dangerous.

GOOD LUCK!

[MOTOXMAN]

Will the pitch error compensation fix interpolations of holes and pins in the effected area? I need to make a pin that is .187 in diameter +0/-.001 (all dimensions in inches). In the unaffected areas this is no problem.

Thanks,

[zavateandu]

yeah this is the mean of this option on fanuc

but check parameters 3620,3621,3623,3624 to see if this option is active or not

ps:i sent u a private message check it

GOOD DAY!

[underthetire]

Pitch error works well for this kind of problem. Not all machines are set up for pitch comp though. You will also need a laser or at minimum a table step gauge to set it up. Expect to spend some real time to get it correct. I've done several of them, and usually its 1 day to three weeks to get a machine in that close. And once it's done, you still have no guarantee that the pin would be round. You would really need to run a ballbar and do some servo tuning after that. Our target machines here spec at .00005 over full travel, so I can spend weeks dialing in a machine.

[MOTOXMAN]

OK, maybe I am jumping to conclusions. When I got the machine new I did not have this problem. Could it be something else besides the screw or the pitch of the screw?

[MOTOXMAN]

OK I checked the ball screw alignment and it was not even close. In fact on the end of the screw (with out the drive) I had to grind the holes out to get the screws in without a bind. After that I checked for backlash and found that it only got a little better about .0006. I then checked the backlash of the nut and found none. I found the nut to be flexing on the mount and the mount also flexing to the table. The combination of the two gave me .0007. This was when the nut was near the right of the screw. When I moved to the left of the screw I found no flexing. What is going on? I have ran the machine rotating the vises over the entire table to make for even wear. It has been like this since I got the machine. Could the machine be flawed?