FANUC 0i-F OT0500 after power-up, limits seem to have moved: what to check?
I'm getting an OT0500 (+ OVERTRAVEL (SOFT 1)) alarm on my FANUC 0i-F after power-up. The machine position looks wrong, and the software travel limits seem to have shifted. What should I check first?
The OT0500 alarm on a FANUC 0i-F indicates that an axis has exceeded its positive-side software travel limit, which is set by parameter 1320. This limit is in machine coordinates, so its accuracy depends on the axis's reference position. If the alarm occurs after power-up and the limits appear to have moved, it often points to an issue with the reference position.
Likely causes and checks
1Reference position wrong or lost
- Points to it
- The software travel limits are based on machine coordinates, which rely on a correct reference position. If the reference position is lost or incorrect, the machine's understanding of its position relative to the limits will be wrong, making the limits appear to have moved.
- Check
- Check the alarm history for DS0300/DS0306, which are related to reference position issues. If found, re-establish the reference position according to the machine builder’s procedure before trusting the software limits.
2Program, work offset or tool offset sends the axis beyond travel
- Points to it
- If the machine reference is otherwise correct, an automatic operation might be commanding the axis beyond the set software limit due to an error in the program, active work offset, or tool length/wear offsets.
- Check
- Review the program block where the alarm occurs, specifically checking the end point in machine coordinates, the active work offset, and any relevant tool length or wear offsets.
3Operator jogged past the limit
- Points to it
- In manual mode, an operator can inadvertently jog an axis beyond the software travel limit, triggering the OT0500 alarm.
- Check
- Jog the alarmed axis back in the opposite direction. Then, press the RESET button. Note that if parameter 1301#4 (OF1) is set, the alarm will clear automatically once the axis is moved back within range.
4Stroke limit parameters changed
- Points to it
- The software travel limits are defined by parameters 1320 (positive side) and 1321 (negative side). If these parameters have been altered, the limits will change, potentially causing unexpected overtravel alarms.
- Check
- Compare the current values of parameters 1320 and 1321 with the machine builder's backup parameters to identify any unauthorized or incorrect changes.
Next check: Given that the alarm occurred after power-up and the limits seem to have moved, the most likely cause is a lost or incorrect reference position. Therefore, you should first check the alarm history for DS0300/DS0306 and re-establish the reference position as per the machine builder's instructions.
Related questions
Describe the fault or upload a photo, and InduQT checks it against the manufacturer manuals. Share the result here when it helps someone else.