OT0503

Review Program Code

Access the active program in the CNC control and check the coordinates for the affected axis. Look for negative values that exceed the software limit setting.

Use the program simulation mode if available to visually confirm the tool path without moving the machine.

Ensure the machine is in a safe state before accessing or editing programs to avoid accidental movement.

Compare with Software Limit

Navigate to the parameter settings (typically under PMC or system parameters) to view the negative software limit for the affected axis. Compare this with the programmed coordinates.

Document the current limit values before making changes for future reference.

Incorrect parameter access can cause system errors; proceed with caution.

Modify Program Coordinates

If the programmed coordinates exceed the limit, edit the program to stay within the acceptable range. Test the modified program in dry-run mode to confirm the issue is resolved.

Consider adding safety margins in the program to avoid future limit violations.

Always back up the program before editing to prevent data loss.

Access Software Limit Parameters

Using the CNC control panel, navigate to the axis parameters (often under Parameter No. 1320 for negative limits on FANUC systems) to view the current negative limit setting for the affected axis.

Refer to the machine’s parameter manual for the exact parameter number if 1320 is not applicable.

Do not alter parameters without proper authorization as it can affect machine safety.

Verify Against Machine Specs

Compare the current negative limit value with the manufacturer’s recommended or previously documented value. Check for discrepancies that might indicate an error or corruption.

If unsure of the correct value, consult the machine’s original setup documentation or OEM support.

Incorrect limits can lead to mechanical damage; double-check values before proceeding.

Adjust Limit if Necessary

If the limit is set incorrectly, adjust the parameter to the correct value. After changing, perform a slow test move to ensure the axis operates within the new limit without triggering alarms.

Make incremental changes and test after each adjustment to avoid over-correcting.

Ensure a backup of all parameters is created before making changes.

Inspect Axis for Obstructions

Visually inspect the affected axis for debris, tools, or other obstructions that might prevent full travel or cause position errors. Clear any obstructions found.

Use compressed air or a soft brush to clean hard-to-reach areas without disassembling components.

Power down the machine and lock out/tag out before physical inspection to prevent accidental movement.

Check Axis Position Feedback

Use the CNC diagnostic screen to verify the current position feedback of the axis. Compare this with the actual physical position to detect discrepancies indicating calibration loss.

If feedback is off, a home position reset (zero return) may be required after clearing obstructions.

Avoid manual movement of the axis without confirming power isolation.

Perform Zero Return Procedure

If calibration is suspected to be off, perform a zero return or homing procedure for the affected axis as per the machine manual. Monitor for errors during the process and retest operation.

Mark the physical home position before resetting to ensure accuracy during re-homing.

Ensure no personnel are near moving parts during zero return to avoid injury.

Check System Event Log

Access the CNC control’s event or alarm history to check for recent power failures, memory errors, or improper shutdowns that might indicate parameter corruption.

Look for alarms like ‘SRAM error’ or ‘Battery low’ which often precede data corruption.

Do not ignore battery warnings as they can lead to total data loss.

Verify Parameter Backup

If a backup of parameters exists, compare current software limit values with the backup to identify discrepancies. Note any differences for the affected axis.

Always maintain an up-to-date parameter backup on an external device or server.

Avoid overwriting backups without confirming current data integrity.

Restore Parameters if Corrupted

If corruption is confirmed, restore parameters from the backup using the CNC control’s data input procedure. Test machine operation after restoration to ensure the alarm is cleared.

After restoration, perform a full system check to ensure other parameters are unaffected.

Incorrect restoration can cause additional alarms; follow the manual precisely.

Perform System Reset

Power down the CNC machine completely, wait for 5 minutes, then power it back up to clear any temporary glitches in the control system. Monitor for recurrence of the alarm.

Ensure all programs and data are saved before resetting to avoid loss.

Follow proper shutdown procedures to prevent data corruption during reset.

Check Firmware Version

Access the system information screen on the CNC control to check the current firmware version. Compare it with the latest version available from FANUC to see if an update is needed.

Contact FANUC support for release notes on firmware updates to confirm if they address limit-related issues.

Do not attempt firmware updates without proper training or support.

Update Firmware if Necessary

If the firmware is outdated and known to cause limit issues, follow FANUC’s update procedure to install the latest version. Test the machine after the update to confirm resolution.

Backup all system data and parameters before updating firmware as a precaution.

Firmware updates can cause system instability if not done correctly; consider professional assistance.