X home problem with Hardinge T51SP with Fanuc 18 T

Ox, or anyone else familiar with the old Hardinge lathes,

My old T51 SP with Fanuc 18 T did something strange today. It sat for a few weeks (maybe the turret dropped down off of home), and now it doesn’t seem to know where x home is. Same parts, same program and everything, but when I hit cycle start the turret approached the part more than an inch too low in x and alarmed out as the toolholder started rubbing the part face because the cutting insert was over an inch below the part. I was able to power off/on and travel the turret out to where I could do the home procedure. Although the home procedure worked at first this morning and let me cycle start the program, now it keeps moving up a bit and then alarms out with an x+ over travel. Looking at the turret, it does not seem to be high enough in x to even be at home much less over-travelled. My guess is, that first homing this morning never went all the way up in x, but somehow still registered as x home position. That set the x coordinates 1 inch lower than they should have been. Does that sound possible? Is there a way (like special start up procedure of Cancel + P + power on) to make it stop giving the x+ over travel alarm during homing procedure? If so, I can call a tool and use Jog to touch the part and see if the coordinates are where they should be.

Any help is greatly appreciated.

-Gene

Did you check for sticky decel, homing switches?

I have an 18M that if the head drifts down for some reason (rarely happens, power goes out) or you hand crank a X Y ballscrew in the wrong direction it will give an OT alarm before it homes. Cancel + P while powering up bypasses the soft limits and allows it to home as you mentioned.

The special power up did get it to go home properly. I touched the part and verified that the coordinates are right. I re-homed it and hit cycle start again. The program is running, and my fingers are crossed. Thanks so much for confirming that the cancel + P was the thing to try.

-Gene

Tungsten Carbide said:

The special power up did get it to go home properly. I touched the part and verified that the coordinates are right. I re-homed it and hit cycle start again. The program is running, and my fingers are crossed. Thanks so much for confirming that the cancel + P was the thing to try.

-Gene

Click to expand...

Once it homes I do not know if the soft limits are still bypassed because of the cancel + p so I have always powered the machine back down and then reboot it without any fancy button combos. I don't know if this is necessary but I always figure better safe than sorry when it's something as simple as off and on again.

Maybe someone more knowledgeable with Fanuc than myself can chime in and confirm or deny my suspicions.

Hardplates said:

Once it homes I do not know if the soft limits are still bypassed because of the cancel + p so I have always powered the machine back down and then reboot it without any fancy button combos. I don't know if this is necessary but I always figure better safe than sorry when it's something as simple as off and on again.

Maybe someone more knowledgeable with Fanuc than myself can chime in and confirm or deny my suspicions.

Click to expand...

Hello Hardplates,
Yes, you have to cycle the power to the control after Cancel+P and Reference Return to invoke the soft limits.

Regards,

Bill

Thanks Bill. I have been running it without re-starting it, but that probably is not the safest.

- Gene