The FANUC SV404 alarm is related to the servo ready signal of the servo amplifier. This alarm occurs when the servo amplifier's VRDY signal, also known as the servo ready signal, remains ON continuously when the CNC system detects an abnormal servo ready status.
In normal operation, the CNC system checks the ready status of the servo amplifier before enabling servo control. If the VRDY signal stays ON abnormally, the system may judge that the servo ready circuit, amplifier, or axis control hardware is not operating correctly, and the SV404 alarm may appear.
What Does FANUC SV404 Alarm Mean?
SV404: Servo Ready Signal Stays ON
The FANUC SV404 alarm means that the servo amplifier's servo ready signal (VRDY) remains ON. This signal is used by the CNC system to confirm whether the servo amplifier is ready for operation.
When this signal stays ON continuously under abnormal conditions, the CNC system may stop servo operation and display the SV404 alarm to protect the machine and servo control system.
Common Causes of FANUC SV404 Alarm
The most common causes of FANUC SV404 alarm include:
1. Abnormal VRDY Signal from the Servo Amplifier
The VRDY signal is the servo ready signal from the servo amplifier. If this signal remains ON abnormally, the CNC system may detect an incorrect ready status and generate the SV404 alarm.
This may be caused by an internal fault in the servo amplifier, a signal circuit abnormality, or a mismatch in the servo control status.
2. Servo Amplifier Failure
A damaged or faulty servo amplifier can cause the VRDY signal to stay ON incorrectly. In this case, the CNC system may not be able to correctly judge the actual servo ready condition.
If the alarm appears after the amplifier has failed, been replaced, or suffered from power-related damage, the servo amplifier should be checked carefully.
3. Axis Card or Servo Control Board Failure
The SV404 alarm may also be caused by a damaged axis card or servo control board. If the CNC system cannot correctly receive or process the VRDY signal, it may report a servo ready signal abnormality.
When the amplifier appears normal but the alarm still occurs, the axis card and related control hardware should also be inspected.
4. Special Machine Configuration or Parameter Requirement
In some special cases, the alarm may be related to the machine configuration or signal handling method. For certain applications, the alarm can be masked by setting parameter P1800#1 = 1.
However, this parameter setting should only be used when the machine configuration allows it and the hardware condition has been properly confirmed. It is not recommended to mask the alarm before checking whether the amplifier or axis card is damaged.
How to Troubleshoot FANUC SV404 Alarm
When troubleshooting the FANUC SV404 alarm, the main point is to check why the servo ready signal (VRDY) remains ON.
You may need to check:
- Whether the alarm appears immediately after power-on
- Whether the servo amplifier has been recently replaced
- Whether the amplifier shows any other alarm or fault indication
- Whether the axis card or servo control board is functioning correctly
- Whether there is any abnormal signal status related to VRDY
- Whether the machine uses a special configuration requiring parameter masking
- Whether parameter P1800#1 is suitable for this machine condition
Because SV404 may involve servo amplifier hardware, axis card hardware, and CNC parameter settings, it is important to check the system carefully before changing parameters or replacing parts.
Recommended Solution
For FANUC SV404 alarm, the recommended solution depends on the actual cause of the alarm.
1. Mask the Alarm in Special Cases
In certain special applications, the alarm may be masked by setting parameter P1800#1 = 1. This method is only suitable for specific machine configurations where the signal condition is known and confirmed.
Before changing this parameter, make sure the machine condition has been checked properly. If the alarm is caused by actual hardware failure, simply masking the alarm may hide the real problem and create further risk.
2. Replace the Servo Amplifier or Axis Card
If the SV404 alarm is caused by a damaged servo amplifier or axis card, the faulty hardware should be repaired or replaced.
In many cases, the alarm may be related to abnormal signal output from the amplifier or abnormal signal processing by the axis card. Replacing or repairing the damaged amplifier or axis card can help restore normal servo ready signal operation.
If your machine shows FANUC SV404 servo ready signal alarm, please contact REACO CNC directly. Our team can help check the possible cause and provide suitable FANUC servo amplifier, axis card, repair, or replacement solutions.
REACO CNC Support for FANUC SV404 Alarm
REACO CNC provides support for FANUC CNC systems, servo amplifiers, axis cards, servo control boards, and related CNC hardware issues.
We can help with:
- FANUC CNC alarm analysis
- FANUC SV404 alarm troubleshooting
- Servo amplifier checking and replacement
- Axis card and servo control board inspection
- FANUC CNC board repair
- Servo ready signal issue analysis
- Replacement FANUC CNC parts supply
- Technical support for FANUC servo system problems
If you are not sure whether the SV404 alarm is caused by the servo amplifier, axis card, parameter setting, or another CNC hardware issue, you can send us the CNC system model, amplifier model, alarm screen, board photos, and machine information. Our team will help check the possible cause.
FAQ About FANUC SV404 Alarm
What is FANUC SV404 alarm?
FANUC SV404 alarm means that the servo amplifier's servo ready signal, also called VRDY, remains ON abnormally.
What causes FANUC SV404 alarm?
The alarm may be caused by an abnormal VRDY signal, servo amplifier failure, damaged axis card, or special machine configuration requiring parameter adjustment.
Can FANUC SV404 alarm be masked by parameter setting?
In some special cases, the alarm can be masked by setting parameter P1800#1 = 1. However, this should only be done after confirming that the alarm is not caused by actual hardware failure.
Can a damaged servo amplifier cause SV404 alarm?
Yes. If the servo amplifier is damaged and the VRDY signal remains ON abnormally, the CNC system may display the SV404 alarm.
Can a damaged axis card cause SV404 alarm?
Yes. If the axis card or servo control board cannot correctly process the servo ready signal, the SV404 alarm may occur.
How can I fix FANUC SV404 alarm?
The VRDY signal, servo amplifier, axis card, and related parameter settings should be checked. In special cases, parameter P1800#1 = 1 may be used to mask the alarm. If the alarm is caused by hardware failure, the servo amplifier or axis card should be repaired or replaced.
Need Help with FANUC SV404 Alarm?
If your CNC machine has a FANUC SV404 servo ready signal alarm, please contact REACO CNC. We can help analyze the alarm cause and provide suitable FANUC CNC repair, servo amplifier replacement, axis card replacement, or technical support.
Reference Source: Beijing FANUC. This article is based on technical documentation provided by Beijing FANUC. For More Fanuc CNC repair Cases and technical articles, please back to Fanuc Technical Support Center.
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