SV0367 Count Miss (Built-in) fault in Fanuc drive

SV0367 Count Miss (Built-in) fault in Fanuc drive

Description

SV0367 is a "Count Miss" alarm. While similar to "Pulse Miss," this specifically refers to the serial counter logic. The encoder sends position data in packets. The CNC predicts what the next count should roughly be based on current velocity. If the received count differs wildly from the prediction, or if the internal checksum of the count data is invalid, SV0367 is triggered. It is effectively a data corruption alarm.

Cause

This is almost always noise or cable impedance issues.

• Electrical Noise: Running the encoder cable next to a high-voltage welding cable or EDM power supply.
• Cable Length: Exceeding the maximum specified length for the feedback cable (typically 20-30m) without a repeater, causing signal attenuation.
• Ground Loops: Differences in ground potential between the motor frame and the CNC cabinet.

Solution

1. Check Shielding: This is the #1 fix. Ensure the cable shield is clamped 360-degrees at the drive entry.
2. Ferrite Cores: Install a ferrite core (noise choke) on the feedback cable near the drive.
3. Separate Cables: Physically separate the motor power cable and the encoder feedback cable in the raceways. They should not run parallel for long distances if possible.