Fanuc Alarm 500 — What It Means
Fanuc Alarm 500 is an overtravel alarm — one or more axes traveled beyond the software overtravel limits stored in the machine parameters. Unlike hardware overtravel alarms (1-4 series), Alarm 500 is a software position check; the control detected that the commanded path would enter or has entered the software travel boundary.
Common Causes
- Machine returned to wrong reference position — After a power cycle or battery change, if the reference return wasn’t completed correctly, the machine’s position understanding is wrong and normal moves trigger 500.
- Part offset or work coordinate set incorrectly — A work coordinate (G54-G59) or tool length offset that positions the program path outside the machine travel envelope triggers 500.
- Program error — A G-code program commanding a position beyond the machine’s soft limits triggers 500 before the move executes.
- Soft limit parameter changed — Incorrect or reduced travel limits in machine parameters cause normal positions to trigger Alarm 500.
Step-by-Step Fix {#fix}
- Identify which axis triggered 500 — The Fanuc alarm display shows the axis designation. Note it.
- Check current position vs. soft limits — On the Fanuc position display, compare the current machine coordinate to the soft limit values in parameters (typically P1320/P1321 for positive/negative limits per axis).
- Re-execute reference return — If position is uncertain after a power cycle, execute ZRN (reference return) on all axes before any other motion.
- Check work coordinates and offsets — Verify G54 (or active work coordinate) and tool length offsets are correct for the current setup.
- Manual jog out of limit — If the axis is inside the soft limit boundary, use the [OVR cancel] function (hold RESET and press the positive or negative axis jog button on some Fanuc versions) to jog out of the soft limit zone.
Parts Often Needed
| Part | Notes |
|---|---|
| Backup battery | Amazon | If position was lost due to battery failure |
When to Call a Pro
If Alarm 500 triggers on moves that were previously fine, a parameter change or position calibration issue needs Fanuc-certified service to diagnose.