FANUC Series 0i-F / 0i-F Plus alarm OT0500: + OVERTRAVEL (SOFT 1)
OT0500 (+ OVERTRAVEL (SOFT 1)) on a FANUC 0i-F means an axis exceeded the positive-side stored stroke check 1, the software travel limit set in parameter 1320; OT0501 is the same on the negative side (parameter 1321). The limit is in machine coordinates, so it is only as accurate as the axis’s reference position.
Diagnose this with AI
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When it happens
- Jog or handwheel near the end of travel
- Automatic operation with a command beyond the limit
- After power-up when the reference position is not correct
Likely causes and checks
1Program, work offset or tool offset sends the axis beyond travel
- Points to it
- Happens in automatic operation at a particular block; machine reference is otherwise correct.
- Check
- Check the block’s end point in machine coordinates, the active work offset and the tool length or wear offsets.
2Operator jogged past the limit
- Points to it
- Manual mode; alarm only stops the jogged axis.
- Check
- Jog the axis back in the opposite direction, then press RESET (unless parameter 1301#4 OF1 is set, which clears the alarm as soon as the axis is back in range).
3Reference position wrong or lost
- Points to it
- Limits seem to have moved; machine position looks wrong after power-up, a battery alarm, a crash or motor work.
- Check
- Check the alarm history for DS0300/DS0306 and re-establish the reference position per the builder’s procedure before trusting the limits.
4Stroke limit parameters changed
- Points to it
- Started after a parameter load or edit.
- Check
- Compare parameters 1320 and 1321 with the builder’s backup.
Telling it apart
- OT0506/OT0507 (OVERTRAVEL (HARD)) are the physical stroke-end limit switches; FANUC notes they stop all axes in automatic operation and only the alarmed axis in manual.
- OT0510/OT0511 (PRE-CHECK) come from the stroke check before move: the block end point or path was found in the forbidden area before the axis moved, so the program needs changing.
- OT0502–OT0505 are stored stroke checks 2 and 3 (fixtures, chuck/tailstock barriers), not the travel limits.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| 1320 | Stored stroke check 1, positive direction | Positive software travel limit in machine coordinates (OT0500). |
| 1321 | Stored stroke check 1, negative direction | Negative software travel limit in machine coordinates (OT0501). |
| 1301#4 (OF1) | Cancel OT alarm when back in range | 0: alarm stays until RESET after moving back into range; 1: alarm cancels immediately. |
| 1300#6 (LZR) | Stroke check before reference return | With 1311#0 DOT = 1, sets whether the check runs before the first manual reference return after power-on. |
Evidence to collect
- Axis, direction and machine position at the alarm
- Program block, active work and tool offsets
- Alarm history for APC or reference alarms
- Parameters 1320/1321 vs the builder’s backup
Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.