SP9007 (Alarm 07) Spindle Overspeed fault in Fanuc drive

SP9007 (Alarm 07) Spindle Overspeed fault in Fanuc drive

Description

SP9007 is a dangerous fault condition. It indicates that the spindle motor's actual RPM has exceeded the maximum rated speed (typically by 115%). For example, if the max speed is 10,000 RPM, the alarm might trip at 11,500 RPM. This is a hardware safety trip generated by the drive's CPU to prevent the motor rotor from disintegrating or the tool from being thrown due to centrifugal force.

Cause

This is often a "Loss of Load" or "Feedback Gain" issue.

• Loss of Feedback: If the encoder belt breaks while cutting, the motor stops sending pulses. The drive thinks the motor is stopped, so it dumps max current to speed it up. If the belt catches momentarily, the drive sees a massive speed spike.
• Parameter Error: The "Max Speed" parameter (e.g., 4020) is set incorrectly or the Gear Ratio parameters are wrong.
• Regen Failure: If the spindle tries to brake but the regen circuit fails, the motor may accelerate uncontrollably (runaway) before tripping.

Solution

1. Check Encoder Coupling: Inspect the belt or coupling connecting the motor to the spindle speed sensor.
2. Review Parameters: Did this happen after a memory reload? Check the maximum RPM settings in the Spindle Parameter manual.
3. Tachometer Test: (Advanced) Use an external tachometer to verify if the spindle is actually going that fast, or if the sensor is just reporting noise. If the spindle is physically slow but the screen says 20,000 RPM, the sensor is faulty.