135

Check Battery Voltage

Locate the battery compartment on the control unit or servo amplifier. Use a multimeter to measure the voltage; it should be within the manufacturer's specified range (typically 3.6V for lithium batteries).

Always keep spare batteries on hand with the correct part number for your Fanuc model.

Ensure machine power is off before accessing the battery compartment to avoid electrical shock.

Replace Battery if Low

If voltage is below spec or battery is over 2 years old, replace it with a compatible battery. Follow Fanuc manual for correct replacement procedure to avoid data loss.

Replace the battery with power on if possible to retain position data temporarily, if supported by your model.

Incorrect battery type can damage the system; double-check part compatibility.

Verify Alarm Clearance

After replacement, power cycle the machine and check if Alarm 135 clears. If it persists, proceed to re-referencing the machine as position data may still be lost.

Document the date of battery replacement for future maintenance scheduling.

Do not operate the machine until the alarm is cleared to avoid positional errors.

Check Error Logs

Access the diagnostic screen on the Fanuc control panel and look for specific encoder-related errors or faults in the servo system logs.

Use the Fanuc diagnostic parameter (e.g., DGN 200-204) to pinpoint encoder issues quickly.

Ensure you are familiar with the control interface to avoid accidental parameter changes.

Inspect Encoder Connections

Physically inspect the encoder cables and connectors for loose connections, corrosion, or damage. Secure or replace as needed.

Use dielectric grease on connectors to prevent future corrosion in humid environments.

Power off the machine before handling encoder cables to prevent electrical hazards.

Test Encoder Output

Use a diagnostic tool or oscilloscope to test the encoder output signals (A/B/Z phases) for consistency. If signals are erratic or absent, the encoder likely needs replacement.

Compare readings with a known good axis encoder to identify discrepancies.

Improper testing can damage the encoder; consult the manual for correct test points.

Review Operation Logs

Check the CNC control panel for logs or timestamps indicating a sudden power interruption or improper shutdown event.

Enable power failure detection alarms if your system supports it to log such events automatically.

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Inspect Power Supply

Verify the stability of the incoming power supply and check for tripped breakers or blown fuses that could indicate a power interruption.

Consider installing a UPS (Uninterruptible Power Supply) for critical machines to prevent future issues.

Work on electrical systems should only be done by qualified personnel to avoid injury.

Re-Reference Machine

If power loss is confirmed, perform a home reference procedure as per the Fanuc manual to restore absolute position data.

Mark reference points physically on the machine to speed up future re-referencing.

Ensure all axes are clear of obstructions before homing to prevent collisions.

Visually Inspect Cables

Examine all encoder and feedback cables for cuts, fraying, or pinch points along their length, especially near moving parts.

Route cables away from high-traffic or moving areas to prevent future damage.

Power off the machine before inspection to avoid electrical hazards.

Test Cable Continuity

Use a multimeter to test continuity of each wire in the encoder cable. Replace any cable with broken or intermittent connections.

Label cables during testing to avoid mix-ups during reassembly.

Incorrect testing can give false readings; ensure proper multimeter settings.

Secure or Replace Connectors

Check connectors for bent pins or loose fittings. Secure or replace damaged connectors, then retest the system for alarm clearance.

Use cable ties or protective sleeves to secure cables after repair.

Ensure machine is powered off during connector work to prevent shorts.

Check Parameter Settings

Access the parameter screen on the Fanuc control and verify that absolute position parameters (e.g., 1815#4) are set correctly per the manual.

Backup parameters before making changes to avoid accidental data loss.

Incorrect parameter changes can cause further issues; proceed with caution.

Update or Reload Software

If parameters are correct but the issue persists, check for software updates or reload the control software from a backup if corruption is suspected.

Contact Fanuc support for the latest software version compatible with your system.

Software reloads can erase settings; ensure backups are available.

Test Control Unit

If software and parameters are intact, test the control unit with diagnostic tools or swap with a known good unit to isolate the issue.

Document all test results to assist Fanuc support if escalation is needed.

Control unit testing should only be performed by trained personnel.