369

Power off the machine completely. Inspect the serial pulse coder cable (typically separate from power cables on αi/βi motors) at both the motor connector (JE1) and amplifier connector (JA7A for α series, varies by amplifier model). Check for physical damage, oil contamination, bent pins, or loose locking mechanisms.

Always power down before disconnecting encoder cables to prevent data corruption or component damage.

Disconnect and reconnect the encoder cable at both ends, ensuring proper seating and locking. Clean connectors with electronics contact cleaner if contamination is visible. Verify cable routing is secure and not subject to excessive flexing or proximity to motor power cables.

If available, swap the encoder cable with a known-good spare or from an operational axis. Power on and test. If alarm clears, replace the defective cable. Check cable part number compatibility with motor model (serial vs parallel interface).

Check amplifier LED status during alarm condition. For αi/βi amplifiers, LED pattern will indicate encoder communication fault (typically alternating red/green on POWER LED). Consult amplifier hardware manual for specific LED fault codes corresponding to serial pulse coder errors.

Access DIAGNOSIS screen > select affected axis > check diagnostic numbers D300-D303 (encoder position data) and D400 (serial communication error counter). If D300-D303 show erratic values or no change during manual rotation (power off, in EMERGENCY STOP), encoder may be faulty.

Use caution when manually rotating axes - ensure EMERGENCY STOP is active and no workpiece/tooling creates pinch points.

Check parameter 2020 (encoder type setting) for the affected axis. Verify setting matches actual motor encoder type: serial pulse coder (αi series typically = 4 or 5). Incorrect parameter causes communication protocol mismatch.

Perform encoder resistance test. With power off and encoder cable disconnected from amplifier, measure resistance between encoder power pins (typically +5V and 0V) - should be 50-150Ω. Infinite resistance indicates open circuit in encoder. Short circuit (<10Ω) indicates encoder failure.

Disconnect encoder cable from AMPLIFIER side only to isolate encoder for testing.

If diagnostics and testing indicate encoder failure, replace the motor or encoder assembly. After replacement, perform reference position return (zero return) and verify parameter 1815 (serial pulse coder setup) matches new encoder specifications. Run servo guide for tuning verification.

Verify encoder cable routing is separated from motor power cables (U, V, W) by minimum 100mm. Ensure encoder cable uses shielded twisted-pair construction with shield grounded at amplifier end only (not both ends to avoid ground loops).

Check main cabinet and motor grounding. Verify motor PE (protective earth) is connected with low-resistance path (<0.1Ω) to cabinet ground. Check amplifier mounting surface has proper ground contact. Poor grounding increases noise susceptibility.

Inspect for nearby noise sources: VFD spindle drives, welding equipment, or recently installed devices. If alarm is intermittent and correlates with other equipment operation, install ferrite cores on encoder cable or add line filters to noise-generating equipment.

Check parameter 1900-1903 (serial pulse coder gear ratio settings). Incorrect settings can cause data framing errors interpreted as transmission faults. Verify against motor specifications. Monitor alarm occurrence frequency - if random/intermittent under normal conditions, noise is likely cause.