FANUC Series 0i-F / 0i-F Plus alarm SV0436: SOFTTHERMAL(OVC)
SV0436 (SOFTTHERMAL(OVC)) on a FANUC 0i-F means the digital servo software detected a software thermal (OVC) condition: the motor current stayed high for long enough that the servo’s thermal model calls it an overload. It protects the motor before the winding itself overheats.
Diagnose this with AI
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When it happens
- After a period of heavy cutting or repeated rapid moves
- On a vertical axis holding a load
- After a crash or a mechanical change
Likely causes and checks
1Mechanical drag or binding
- Points to it
- One axis only; load higher than usual even on light moves; noise or rough motion when jogging.
- Check
- Compare that axis’s load with the other axes on the same move; inspect ways, lubrication, gibs, ballscrew and support bearings.
2Brake dragging
- Points to it
- Braked axis; load high from the first move and the motor runs warm.
- Check
- Check the brake releases fully when servo is on.
3Cycle duty too heavy
- Points to it
- Appears late in a long cycle with frequent rapids or heavy cuts; clears after cooling.
- Check
- Review cutting conditions and rapid/acceleration duty for the axis.
4Gravity axis balance
- Points to it
- Vertical axis only; high holding current at standstill.
- Check
- Check the counterbalance (if fitted) and compare holding load with the builder’s figures.
Telling it apart
- SV0430 (SV MOTOR OVERHEAT) is the measured motor temperature; DGN 308 shows winding temperature and FANUC sets the motor overheat alarm at 140 °C (284 °F).
- SV0438 (SV ABNORMAL CURRENT) is an instantaneous overcurrent, typically a short or ground in the motor or cable rather than sustained load.
- SV0024 (PS SOFT THERMAL) is the same kind of check on the power supply module rather than the axis.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| DGN 308 (diagnosis) | Servo motor temperature (°C) | Winding temperature; motor overheat alarm at 140 °C (284 °F). |
Evidence to collect
- Axis and load reading over the cycle
- DGN 308 motor temperature
- Brake and lubrication condition
- Program duty: rapids and cut depth around the alarm
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