SV0409 Abnormal Torque Load (Collision) fault in Fanuc drive

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SV0409 Abnormal Torque Load (Collision) fault in Fanuc drive

Description

SV0409 is a protective alarm designed to minimize damage during a crash. Modern Fanuc drives utilize "Collision Detection" or "Unexpected Load Detection." The drive learns the normal friction and cutting load of the machine. If the torque suddenly spikes—for example, if the spindle runs into a fixture or a drill breaks and jams—the drive detects this anomaly within milliseconds. It triggers SV0409 and often reverses the motor direction slightly to relieve pressure. This is different from a thermal overload; it is an instantaneous reaction to impact.

Cause

While a crash is the obvious cause, false positives can occur.

  • Physical Collision: The operator jogged the machine into a clamp, or the tool length offset was incorrect, causing a crash.
  • Chip Jam: A large build-up of metal chips has wedged between the way cover and the table, creating a sudden resistance point.
  • Dull Tooling: As a drill or tap dulls, the torque required to cut increases exponentially. If it exceeds the threshold, the alarm trips.
  • Cold Start: In very cold shops, the grease in the bearings is thick. The initial movement might require higher torque than the "Abnormal Load" parameter allows.

Solution

Since this is a calculated load alarm, you can adjust the sensitivity.

  1. Check for Damage: Inspect the machine visually. Is the tool broken? Is the axis pressing against a hard stop? If so, carefully hand-wheel the axis away.
  2. Check Load Monitor: View the servo load meter. If the resting load is high, you have a mechanical bind.
  3. Adjust Sensitivity: If the alarm triggers during aggressive cutting but there is no crash, the threshold might be set too low. Check the parameters associated with "Disturbance Torque" (often related to parameters 2016 or 2104).
  4. Re-Initialize: Some systems allow you to "Teach" the normal friction levels again if the machine has aged and naturally has more friction than when it was new.

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