Applicable Systems
Haas CNC Mill (VF/VM Series)
Symptoms
The Haas control displays Alarm 102: SERVOS OFF. The servo drives have been disabled, either intentionally by the operator or due to a safety circuit opening. All axes are unpowered and cannot hold position.
Possible Causes
- E-STOP button pressed or E-STOP circuit wiring fault
- Servo drive overtemperature or overload protection tripped
- Safety relay or safety PLC detected a fault and cut servo power
- Door interlock opened during cycle execution
- Main 24VDC control power supply dropped below minimum threshold
Troubleshooting Steps
- Step 1: Check if the E-STOP button is pressed and release it if so
E-STOP button is in the released (out) position - Step 2: Check the servo drive status LEDs for overtemperature or overload indication
Drive shows green READY LED, no red fault - Step 3: Verify all safety doors are closed and latched
All doors closed, interlock LEDs are green - Step 4: Check the 24VDC control power supply voltage
Voltage is between 22.8V and 25.2V - Step 5: Press RESET and then SERVO ON to re-enable the drives
Servo ON LED illuminates and axes hold position
How to Reset
To reset: 1) Clear the safety circuit fault (release E-STOP, close doors). 2) Press RESET on the control. 3) Press SERVO ON to re-enable the drives. Caution: Ensure no personnel are in the machine envelope before re-enabling servos.
Frequently Asked Questions
- Q: Why do the servos turn off during a cycle?
The servo drives can be disabled by the safety circuit (E-STOP, door open, overload) or by a drive fault. Alarm 102 indicates the safety loop has opened. Check the E-STOP, door interlocks, and drive status.
- Q: Is it normal for servos to turn off when the cycle ends?
No. Servos should remain on after a cycle completes. If they turn off, check for a safety circuit fault or drive overtemperature condition.
Source: Haas Automation Operator's Manual - Alarm Codes, 2023
Category: CNC