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FANUC Controller
Servo/Axis · Intermediate · 30-60 minutes
Fanuc Alarm 457 - n AXIS: ILLEGAL HI HRV (250US)
Alarm 457 indicates an illegal High-speed Response Vector (HRV) setting in the FSSB communication system, specifically related to the 250-microsecond update cycle. This occurs when the HRV parameter configuration is incompatible with the servo amplifier capabilities or when the FSSB communication timing cannot support the requested HRV update rate for the specified axis.
457
Fanuc Alarm 457 - n AXIS: ILLEGAL HI HRV (250US)
FSSB: Illegal HRV Setting
Fanuc alarm 457: FSSB: Illegal HRV Setting. An FSSB (Fanuc Serial Servo Bus) communication or configuration error has been detected. The serial bus link between the CNC and one or more servo amplifiers has a fault.
Root Cause Summary
Alarm 457 indicates an illegal High-speed Response Vector (HRV) setting in the FSSB communication system, specifically related to the 250-microsecond update cycle. This occurs when the HRV parameter configuration is incompatible with the servo amplifier capabilities or when the FSSB communication timing cannot support the requested HRV update rate for the specified axis.
Safety
- Allow motor to cool completely before handling - surface temperatures may exceed 100°C
- Lock out machine power and verify zero energy state before disconnecting motor cables
- Use proper PPE when checking hot motor surfaces to prevent burns
- Ensure the machine is properly grounded to prevent electrical shock hazards.
- When working with electrical components, use appropriate insulated tools and follow all safety procedures.
- Be aware of potential pinch points and moving parts when inspecting the mechanical transmission components.
- If the motor needs to be removed, use proper lifting techniques and equipment to prevent injury.
- Ensure proper grounding and use insulated tools
- Capacitors in the servo amplifier can store a dangerous electrical charge even after the power is turned off. Wait several minutes after disconnecting power before touching any internal components.
- When measuring thermistor resistance, use a multimeter with a high input impedance to avoid loading the circuit and affecting the reading.
- Be careful when working near moving parts, such as the cooling fan. Ensure the machine is in a safe state before performing any inspections or repairs.
- If the motor is heavy, use proper lifting techniques and equipment to avoid back injuries. Get assistance if necessary.
- If the motor has been running at high temperatures, allow it to cool down completely before handling it to avoid burns.
- Disconnect the power supply to the servo drive before disconnecting or connecting any cables to the motor or drive.
- Avoid touching any exposed electrical connections or components while the machine is powered on.
Causes and Fixes
- 1
Check the servo amplifier model on the alarmed axis and verify its HRV capabilities in the amplifier specifications manual.
- 2
Access parameter 1825 (HRV setting) for the alarmed axis and verify the current setting. Common values: 0=disabled, 1=500μs, 2=250μs.
- 3
If amplifier does not support 250μs HRV, change parameter 1825 from 2 to 1 (500μs) or 0 (disabled) as appropriate for the application.
Changing HRV settings may affect machine performance and requires power cycle to take effect.
- 4
Power cycle the control completely and verify alarm clears. Test axis operation and monitor for motion quality changes.
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Always verify with your machine manual or a certified technician before performing service procedures.