Help Please!

[5AXGUY]

My A55 with a Fanuc O-M controller just went nuts. When I try to reference the Z-axis, it slows down as it should, but continues past the soft limit switch until the hard one.
I checked the switch. It works.
I verified that I/O sees it. It does.
I powered down, then up with Can-P held. Nothing new.

What am I missing?

How do I re-establish the Z-axis home? The 1815 parameter does not exist on the O-M.

Help, please!

Peter

[Al_The_Man]

Encoder marker pulse missing?
Al.

[5AXGUY]

Al,

Could be. How do I check?
Thanks
Peter

[ben_heinman]

If you mean bits #4 and #5 of parameter 1815 (APZx and APCx) they would be parameter 21 and 22 of the O-M controls.

[underthetire]

Seen this a bunch of times. The zero switch is either sticking, not releasing after the ramp down of the dog in time, the dog is bent, or chips packed up around it. The Cancel P should have cleared it if it was anything else but a encoder problem. You can try changing the grid shift parameter by like 1 digit to assign a new reference to try. I would not try to fake the ABS parameters on a horizontal cause if your wrong, pallet changing could be exciting.

[Al_The_Man]

Originally Posted by 5AXGUY Al, Could be. How do I check? Thanks Peter

If you have confirmed the slow down switch is not sticking, then trip it manually while homing and see if it stops on the marker, homing it this way mid-travel, allows a longer distance to test for a marker.
Otherwise check cable continuity or use a meter or scope to check for both pulses (Z & /Z).
If using a meter, you have to turn the encoder by hand VERY slowly to catch it.
Al.

[5AXGUY]

Thank you, gentlemen for your responses.

I confirmed that the plunger on the decel side is not sticking. Then I homed it out in the middle of the Z axis travel range by finger-triggering the plunger. But once I moved back to the actual limit switches, it still goes past the decel switch and hits the hard limit. I called a service wizard and we quadruple-verified that the switches work. Then swapped them out and the result is still the same.
I inverted the bits on #21 and #22. That presented with a long list of errors. Then restored the bits. No change.
My service guy packed up and left, defeated, leaving me with a moody machine and an angry boss.
Is there a real procedure for applying the bit change on the parameters? Are you sure #21 and #22 are it?

Is there a source for a set of O-M manuals other than the Fanuc Museum?

Thanks
Pete

[Al_The_Man]

Check you P.M's.
I wonder if you have some kind of large Z grid shift and it hits the O.T. before reaching the grid?
It does not make sense that it zero's anywhere else?
Note what the grid shift is and set it to zero and try again.
Al.

[bmngator]

Sounds like your axis has jump a grid. Switch actuator may moved causing it to come off the decel switch later and the axis hits the hard stop before seeing the encoder marker pulse.

[5AXGUY]

How do I restore or reset or re-calibrate it?

[Al_The_Man]

On a mill, the Z axis grid shift is used to align to a tool changer for example.
The parameter manual I sent should have the grid shift parameter for the Z, it is in encoder counts.
Al.

[5AXGUY]

Gentlemen,

I found the grid shift parameters in #508-#511, with Z in #510. The current value is -5499
I recorded the other values also, just in case I fatfinger something.

Can I start tweaking this number in either direction?
Do I need to put the machine in metric to adjust this parameters?
What is the official or best practice procedure for adjusting it?

Thanks for your help and comments

Peter