+/- Overtravel error for all axis

[claucampan]

I hope it's the right place to post this thread. I've got a BIG problem today with my Heyan CNC, Fanuc 11M control, 3 axis.

When I started the machine today, I've got 6 (six!) errors, 2 for each axis: 1. X+ overtravel (hard); 2. X- overtravel (hard);... and so on for each axis. The machine didn't step on any overtravel limit switch, and it seems (to me) the problem aren't the limit switches.

Can anyone help me to solve this problem, please?

[Dan Fritz]

Sounds like you lost the +24 volt power supply to the limit switches. All of the Fanuc OT switch inputs are "Normally closed", which means that +24 is normal, and 0v will cause the alarm. The switches are all wired so that when the axis travels to the limit, the switch breaks the 24v circuit, putting the control into overtravel. If you loose the +24v supply, you'll get all six OT alarms at once.

Look for a blown fuse on the 24v supply. Depending on how your machine tool builder wired the interface, you might be using the CNCs power supply for the 24v, or you may have a separate little +24v power supply somewhere. In all cases, there are always fuses on the output of these power supplies, which can blow if there's a short somewhere. If you replace a blown fuse and it blows again, look for a limit switch that got coolent or chips inside, causing a short.

[motomitch1]

That just happen to one of are Fanuc 11M controled cnc mills and it was a circuit breaker that suppled power to the 24v power supply so check the input to the supply also.