Mitsubishi CNC controllers are widely used in VMCs, turning centres, and grinding machines across Indian manufacturing plants. When your Mitsubishi CNC displays an alarm, quick diagnosis is essential to minimise downtime. This guide covers the most common alarm codes for the Mitsubishi M70 and M80 series.
Understanding Mitsubishi CNC Alarm Types
Mitsubishi CNC alarms are categorised into several types:
- System Alarms (S): Critical controller faults — machine stops immediately
- Servo Alarms (S/V): Faults in the servo drive or motor system
- Program Alarms (P): Errors in the part program
- Operator Alarms (M): Machine-side faults triggered by the PLC ladder
Common Mitsubishi Servo Alarms
Alarm S01 — Servo Drive Overcurrent
Cause: The servo drive is drawing excessive current. Usually caused by a short circuit in the motor windings, a damaged servo drive power module, or mechanical overload.
Fix: Disconnect the motor and test the drive separately. Check motor winding resistance. Inspect for mechanical binding. Replace the servo drive if the power module is faulty.
Alarm S02 — Servo Drive Overvoltage
Cause: DC bus voltage in the servo drive has exceeded the safe limit. Usually caused by a faulty regenerative resistor or a drive issue.
Fix: Check the regenerative resistor for open circuit. Verify the power supply voltage is within specification. Replace the drive if the internal voltage regulation circuit is faulty.
Alarm S03 — Servo Drive Undervoltage
Cause: DC bus voltage has dropped below the minimum threshold. Usually caused by a power supply issue or a failing drive power supply section.
Fix: Check the incoming AC supply voltage. Inspect the drive's internal power supply. Replace the servo drive if the power supply section is faulty.
Alarm S05 — Servo Motor Overheat
Cause: The servo motor thermal sensor has detected excessive temperature. Caused by overloading, blocked motor cooling, or a failing motor bearing.
Fix: Allow the motor to cool. Check motor cooling fan if fitted. Inspect motor bearings for excessive heat. Reduce cutting load if overloading is suspected.
Alarm S12 — Encoder Error
Cause: Loss of or incorrect encoder (pulse coder) feedback. Usually caused by a damaged encoder cable, faulty encoder connector, or a failed encoder.
Fix: Inspect the encoder cable for damage or loose connections. Swap the encoder with a known good unit. Replace encoder if faulty.
Common Mitsubishi System Alarms
Alarm 1002 — CPU Error
Cause: Internal controller CPU fault. Can be caused by a corrupted program, failing controller battery, or a faulty motherboard (HN767 or similar).
Fix: Replace the CNC battery. Try restarting the controller. If the alarm persists, the motherboard (main board) may need to be replaced.
Alarm 1037 — Parameter Error
Cause: CNC parameters have been corrupted — often after a battery failure.
Fix: Restore parameters from backup. Replace the battery immediately to prevent recurrence.
Mitsubishi CNC Spare Parts from JJ Automation
At JJ Automation, we stock genuine and tested spare parts for Mitsubishi CNC systems including:
- Mitsubishi M70 Motherboards (HN767 and others)
- Mitsubishi Servo Drives and Servo Motors
- Mitsubishi Encoders and Cables
- PCB Boards and Power Supplies
We also provide Mitsubishi CNC repair services and on-site breakdown support across India.
- 📞 Call/WhatsApp: +91 8802212394
- ✉ Email: jj.automation@outlook.com
- 🌐 Website: www.jjautomation.in