What Does SP9031 Mean?
In Fanuc system, SP9031 usually means motor lock or speed signal loss.
Simply put, the control system is turning the motor, but is not receiving the correct speed feedback - that is, the system "feels” that the motor is not moving, or the speed is too far off.
Common symptoms we encounter include:
* One axis of the machine is not moving at all;
* The motor jerks, vibrates or alarms immediately after power-up;
* The red light on the servo drive comes on at the same time as the SP9031.
SP9031 Common Causes
According to years of maintenance experience and customer site feedback, the common triggers of SP9031 are broadly categorized as follows:
1. Failure of speed feedback device (encoder or speed measurement signal abnormality)
If the encoder is broken, or the feedback signal wire is broken or the plug is loose, the system will misjudge it as "motor does not rotate”.
If the encoder is broken or the feedback signal wire is broken or the plug is loose, the system will wrongly judge that the motor is not rotating.
2. Motor is stuck or mechanical load is too large
Sometimes it is not the electronic control problem, but the mechanical part can not move.
We have seen spindle bearing jamming, screw holding, coupling deformation, etc., can lead to SP9031.
You can try to gently rotate the motor shaft by hand (under power failure) to feel whether the resistance is abnormal.
3. Wrong parameter or phase sequence
After installing or replacing the motor, if the parameter is not set correctly, or the phase sequence is reversed, the feedback signal will not be "correct”.
Check against the original parameters, if necessary, restore the factory settings and then debugging.
4. Driver internal failure
Sometimes the problem lies in the amplifier itself, speed detection or power output circuit is damaged, which will make the system false alarms.
In this case, it is recommended to test the speed loop feedback of the driver with a test bench to confirm the point of failure.
5. Loose signal wire or connector
This is actually the most common "hidden fault”. This is actually the most common "hidden fault”. Sometimes the wire is not broken, but the shielding is deteriorating or the plug is loose, so the signal will be intermittent.
Re-plugging the wiring harness, checking the shield ground, and sometimes a small action can make the alarm go away.
Practical Troubleshooting Steps
Step 1 Disconnect safety first
Disconnect the main power supply completely first, and then do it after discharging to avoid electric shock or equipment damage.
Step 2 Reproduce the problem
Record the details of the axis number, working condition, temperature, load, etc., where the alarm appears, and this information will help in the later judgment.
Step 3 Check the mechanical load
Confirm whether the motor shaft can rotate freely; whether the screw, bearing or coupling is stuck.
Step 4 Test the speed feedback signal
Use an oscilloscope or multimeter to test the encoder output; when there is no signal or the waveform is abnormal, prioritize replacing the encoder or repairing the wiring harness.
Step 5 Check the connecting wire
Confirm that the plug is firm and well grounded. If the feedback line has a broken point or the shield is broken, it is very easy to cause intermittent SP9031 alarm.
Step 6 Test the drive
If the motor and signals are OK, put the drive on the Fanuc test bench to test it. Many times, alarms come from speed detection circuit failures.
Step 7 Review parameters and phase sequence
Verify the parameters and check for correct phase sequence. Reversing the phase sequence will cause the speed feedback to "reverse” and the system will report an error.
Repair or Replace?
Generally we recommend:
* Repair if you can: e.g. cable, encoder, plug or parameter problems.
* When you have to replace it: the drive or motor is so damaged internally that it is unstable even if it is fixed.
At Songwei, we save our customers a lot of money every time by using a Fanuc-specific test rig to verify part performance before deciding whether to replace it.
Prevention Tips
* Clean the drive cabinet regularly to prevent short circuits caused by dust and metal shavings.
* Check cables and plugs for looseness or deterioration.
* Keep the equipment environment clean to avoid strong electrical interference.
* Regularly run a self-test with the test platform to detect potential problems early.
What We Can Do for You
As a service provider specializing in CNC automation repair, Songwei offers:
* Fanuc drive, motor repair and encoder signal detection;
* Specialized Fanuc test bench testing services to restore the true running state;
* Provide original, new old and refurbished replacement parts, flexible to meet different budgets;
* Worldwide technical support, covering customers in Europe, North America and Asia.
Our goal is simple - to help you return to production as soon as possible, stable operation of equipment.
Summary
Fanuc alarms SP9031 usually mean abnormal motor speed feedback or lockup. As long as the step-by-step investigation: mechanical → feedback → cable → drive → parameters, most of the problems can be accurately located and repaired.
If you have tried the above methods but the alarm still exists, please feel free to contact Songwei. We can help you remotely diagnose, test the drive or arrange for repairs to get your equipment back into production as soon as possible.
