After loss of ACP (dead batteries) I can't get HOME REFERENCE POSITION to stay where I set it with parameter 1815. Okuma lathe with Fanuc 18T controller, sure is drivin me crazy.

Is this an absolute positioning system with encoder power backed up by battery to maintain track of position?

Yes, as best as I can tell. There are 2 C-size lithium batteries hooked in series to make 6 volts. Power is to maintain track of position; and I have been goin at this like it was absolute positioning. I have been into parameters, and can't really tell if it is absolute. I do know for sure that there are no decelleration switches, just the over travel switches.

I have absolute positioning on my Mits, but I don't know how the setting procedure compares to yours. Something to this effect: first one must find the parameter to turn off absolute positioning (not referring to G90 programming but rather to non-stop monitoring of the position.) Then, the control must be powered down and powered back up. Then, you may need to run through some sort of procedure to reestablish the reference position. Maybe you'll be lucky, and its already set. :D Anyway, you run through that procedure, then find the parameter to turn on absolute position, power the control off and on again, and it should then be ready to go.

Hey HuFlungDung(long name with much meaning), thanks so much for the reply. So far that sounds just like we've been doin, but the home still wanders around. The great thing is, we can move it where we want it, set the parameter to 'position set' and move axis's around and the next thing you know HOME is moved again. I need some super glue. I imagine that there is some stupid and insignificant thing I don't do that then allows things to shift.

How much 'wander' are you getting? Are you powering down, and then powering back up? Do you see any warnings about the reference position being lost when you reboot?

Usually several inches in X or Z, sometimes both are off. Yes, we have been powering down, although not always at the cabinet main disconnect. No warnings, messages, or alarms upon reboot, just an alarm 90(reference position not established). This alarm doesn't show up till we've already noticed our 'distance to go' numbers are way off, then we know we will be seeing ALARM 90.If we are in 'manual mode', home doesn't move, but if we run thru a program, it does. Program could have some problems, but I don't see that as a home movement problem.