The FANUC SP02 Excess Speed Deviation alarm is typically caused by mechanical overload, drive belt issues, or spindle encoder feedback failures. The most likely fix involves inspecting and adjusting cutting parameters or replacing a worn drive belt. If mechanical issues are ruled out, the spindle drive or encoder may require professional servicing.
FANUCSpindleIntermediate30-90 minutes
SP02
FANUC Alarm SP02 - Excess Speed Deviation
Excess Speed Deviation
The actual spindle speed has deviated from the commanded speed by more than the allowable tolerance for longer than the permitted time. The spindle drive cannot maintain the commanded RPM — the motor is unable to reach or hold the target speed. This indicates a drive, motor, or mechanical problem preventing proper speed regulation.
Root Cause Summary
The FANUC SP02 Excess Speed Deviation alarm is typically caused by mechanical overload, drive belt issues, or spindle encoder feedback failures. The most likely fix involves inspecting and adjusting cutting parameters or replacing a worn drive belt. If mechanical issues are ruled out, the spindle drive or encoder may require professional servicing.
Causes and Fixes
1
Check Spindle Load Meter
Run the spindle at the commanded speed and monitor the load meter on the CNC control. If the load exceeds 90-100% before the alarm triggers, the cutting parameters are too aggressive.
Record the load percentage during different operations to identify patterns of overload.
Ensure the machine is in a safe state before running tests to avoid tool or workpiece damage.
2
Reduce Cutting Parameters
Lower the feed rate by 20% or reduce the depth of cut by 0.5mm increments. Test the spindle speed again to see if the alarm persists.
Use the machine’s cutting data handbook to select optimal parameters for the material and tool.
Avoid sudden parameter changes during active cutting to prevent tool breakage.
3
Inspect Tool Condition
Remove and inspect the cutting tool for wear, chipping, or improper setup. Replace or regrind the tool if necessary, then retest the spindle operation.
A dull tool often causes higher load; consider implementing a regular tool inspection schedule.
Wear gloves and eye protection when handling sharp tools.
1
Power Down and Lock Out Machine
Turn off the machine and engage lockout/tagout procedures to prevent accidental startup during inspection.
Always double-check that power is disconnected using a multimeter if unsure.
Failure to lock out can result in severe injury from moving parts.
2
Inspect Drive Belt
Access the spindle drive belt (refer to machine manual for location). Look for cracks, fraying, or excessive wear. Check belt tension using a tension gauge if available.
A belt that feels loose or shows glazing on the surface is likely slipping.
Do not touch belts while the machine is powered on.
3
Replace or Adjust Belt
If the belt is damaged, replace it with the manufacturer-specified part. If loose, adjust tension per the machine manual’s specifications, then test spindle operation at low speed.
Keep a spare belt on hand for quick replacement to minimize downtime.
Over-tightening can damage bearings; follow exact tension specs.
1
Check Encoder Connections
Locate the spindle encoder cable connections at the drive and motor. Ensure connectors are secure and inspect for visible damage or corrosion.
Use a flashlight to check for bent pins in connectors.
Disconnect power before handling electrical components to avoid shock.
2
Test Encoder Signal
Using a diagnostic tool or CNC control diagnostics menu, check for encoder signal errors or missing pulses. Refer to the FANUC manual for specific diagnostic codes.
If unfamiliar with diagnostics, take screenshots of error logs for technician review.
Incorrect handling of diagnostic tools can corrupt data; proceed cautiously.
3
Replace Encoder or Cable if Faulty
If signal errors are confirmed, replace the encoder cable first as it’s a cheaper fix. If the issue persists, the encoder itself may need replacement; consult a technician for this step.
Label cables before removal to ensure correct reinstallation.
Improper encoder installation can cause further alarms; verify alignment.
1
Monitor Drive Status LEDs
Check the spindle drive unit for status LEDs or error codes indicating overcurrent or fault conditions. Refer to the FANUC drive manual for code meanings.
Take a photo of the LED pattern or error display for documentation.
Do not open drive enclosures without proper training due to high voltage risk.
2
Verify Drive Parameters
Access the spindle drive parameters via the CNC control and confirm they match the machine’s specifications (e.g., max current, speed range). Reset to default if discrepancies are found.
Backup current parameters before resetting to avoid losing custom settings.
Incorrect parameter changes can damage the drive; double-check values.
3
Test Drive with No Load
Run the spindle at a low speed (e.g., 100 RPM) with no load. If the alarm still triggers, the drive is likely faulty and requires professional servicing.
Listen for unusual noises from the drive during testing, as they may indicate internal failure.
Avoid prolonged testing if drive overheating is suspected.
1
Listen for Bearing Noise
Run the spindle at a low speed and listen for grinding, whining, or other abnormal noises near the spindle housing, indicating bearing issues.
Use a mechanic’s stethoscope to pinpoint noise sources more accurately.
Keep hands and tools away from moving parts during testing.
2
Check Spindle Temperature
After running the spindle for 5-10 minutes, carefully touch the spindle housing or use an infrared thermometer to check for excessive heat, which suggests bearing friction.
Compare temperature to other machine spindles if available to establish a baseline.
Avoid direct contact with hot surfaces; use proper tools to prevent burns.
3
Inspect and Lubricate Bearings
If safe and accessible, inspect spindle bearings for visible damage or lack of lubrication. Apply manufacturer-recommended grease or oil if needed, or schedule bearing replacement with a technician.
Over-lubrication can cause heat buildup; use only the specified amount.
Bearing replacement requires specialized tools; do not attempt without training.
DIY Feasiblemedium confidence
Call a technician if:
·If encoder or spindle drive diagnostics indicate internal failure after basic checks.
·If spindle bearings are confirmed damaged or seized and replacement is beyond in-house capability.
Prevention
Regularly inspect and replace spindle drive belts as part of preventive maintenance.
Monitor cutting parameters and avoid overloading the spindle during heavy operations.
Schedule annual spindle bearing lubrication and inspection to prevent friction issues.
Common Mistakes
Ignoring high load meter readings and continuing operation, leading to motor or drive damage.
Attempting to adjust spindle drive parameters without proper documentation, causing further alarms.
