Fanuc Soft OT Alarm
A Fanuc soft OT alarm means the axis exceeded a software-defined travel limit. This is different from a hard overtravel where a physical limit switch is hit. The control stopped motion because the machine position exceeded parameter limits.
Common Causes
| Cause | Details |
|---|---|
| Wrong work offset | Program zero shifted too far |
| Machine lost reference return | Absolute position no longer valid |
| Travel limit parameters wrong | After battery loss or bad restore |
| Manual jog past software limit | Common during setup |
How to Clear It
- Put the machine in JOG or HANDLE mode
- Use overtravel cancel / OT release if your machine builder provides it
- Jog the axis back toward the safe travel area
- Re-reference the machine
- Check offsets and parameters before restarting the job
Soft OT vs. Hard OT
| Type | Meaning |
|---|---|
| Soft OT | Control/calculated limit exceeded |
| Hard OT | Physical limit switch activated |
If the alarm clears once the axis is moved back and the machine is re-homed, it was likely a true soft overtravel. If it remains, check limit switches, parameters, and absolute position status.
Bottom Line
Fanuc soft OT alarms are usually caused by bad position data or bad setup data, not failed hardware. Back off the axis safely, re-home, and verify your work offsets.