SV0006

Inspect Axis for Physical Obstruction

Power down the machine and manually move the axis using the handwheel (if available) to check for unusual resistance or binding. Look for debris, chips, or misalignment in the guideways or ball screw.

Use a flashlight to inspect hard-to-see areas of the linear guides for accumulated debris or damage.

Ensure the machine is powered off and locked out to prevent accidental movement during inspection.

Lubricate Moving Parts

Apply the manufacturer-recommended lubricant to the ball screw, linear guides, and other moving components. Follow the machine’s maintenance schedule and ensure no over-lubrication, which can attract debris.

Check the lubrication system (if automated) for proper operation or blockages in delivery lines.

Use only specified lubricants to avoid compatibility issues with seals or components.

Test Axis Movement Post-Lubrication

Power on the machine and run a slow-speed test movement on the affected axis. Monitor for any remaining resistance or alarm recurrence using the diagnostic screen to check following error values.

Record the following error values before and after lubrication to quantify improvement.

Stay clear of moving parts during test operation.

Access Servo Parameters

Using the CNC control panel, navigate to the servo parameter settings (typically under maintenance or diagnostic mode). Locate the gain settings for the affected axis (e.g., position loop gain, velocity gain).

Document the current settings before making any changes for easy rollback if needed.

Incorrect parameter changes can destabilize the system; proceed with caution.

Compare to Recommended Values

Refer to the machine’s manual or Fanuc documentation for recommended servo gain values for the specific axis and machine model. Note any significant deviations in the current settings.

If historical data is available, compare current settings to previously stable configurations.

Do not exceed manufacturer maximums for gain settings to avoid oscillation.

Adjust Gain Incrementally

Increase the position loop gain by small increments (e.g., 10-20% of current value), then test axis movement at low speed. Monitor for alarm recurrence and check if following error decreases via diagnostic display.

Test after each adjustment to avoid over-tuning, which can cause vibration or instability.

Ensure a test program is run in a safe, controlled environment.

Inspect Encoder Connections

Power down the machine and inspect the encoder cable connections at both the motor and control unit for looseness, corrosion, or damage. Secure any loose connectors and look for visible wear.

Use a multimeter to check for continuity in the encoder cable if damage is suspected.

Ensure the machine is locked out before accessing electrical components.

Check Encoder Diagnostic Data

Power on the machine and access the CNC diagnostic screen to check for encoder-related errors or missing feedback signals. Look for irregular pulse counts or alarm sub-codes related to feedback.

Compare feedback data across axes to identify anomalies specific to the affected axis.

Avoid running the machine if feedback loss is confirmed until resolved.

Test with Replacement Encoder (if available)

If diagnostic data indicates encoder failure, temporarily replace the encoder with a known good unit (if available) and test axis movement. Monitor for alarm clearance and proper feedback.

Mark cables before swapping to ensure correct reconnection.

Improper installation can damage the replacement encoder; follow manufacturer guidelines.

Monitor Motor Current Draw

Use the CNC diagnostic screen to monitor the current draw of the affected axis motor during slow movement. Compare against rated values in the manual to identify if the motor is underperforming.

A consistently high current draw may indicate internal motor issues or overload.

Do not operate the motor if current exceeds safe limits to avoid damage.

Check Motor Temperature

After running the axis for a short period, check the motor housing temperature using an infrared thermometer. Excessive heat (beyond manufacturer specs) may indicate internal failure or overload.

Compare temperature with other axis motors to establish a baseline.

Avoid direct contact with hot motor surfaces to prevent burns.

Test Motor Torque Output

If equipped, use a torque testing mode in the CNC control or manually apply a known load to the axis to test motor response. Note if the motor struggles or fails to maintain position.

Document torque test results for comparison with historical data if available.

Ensure safety guards are in place during torque testing.

Perform Backlash Test

Using the CNC control, run a backlash diagnostic program (if available) or manually command small incremental movements in both directions to measure position deviation. Record any significant play.

Use a dial indicator mounted on the axis to measure physical backlash accurately.

Ensure the machine is in a safe mode during testing to avoid unintended motion.

Inspect Ball Screw for Wear

Power down and visually inspect the ball screw for signs of wear, pitting, or damage to the threads. Check for excessive play by manually rotating the screw (if accessible).

Look for uneven wear patterns that might indicate localized stress or misalignment.

Lock out the machine before physical inspection to prevent accidental activation.

Adjust or Replace Ball Screw Components

If backlash exceeds manufacturer tolerance, adjust the ball screw preload (if possible) per the manual. If wear is significant, plan for replacement of the ball screw or related components.

Consult the machine builder for preload adjustment specs to avoid over-tightening.

Improper adjustment can worsen backlash or cause binding; proceed carefully.