Haas Haas CNC Mill (VF/VM Series) Error Code 108

Haas CNC Critical Motor

Model: Haas CNC Mill (VF/VM Series) | Code: 108

Applicable Systems
Haas CNC Mill (VF/VM Series)

Symptoms

The Haas control displays Alarm 108: SERVO OVERLOAD. The servo drive has detected that the motor current has exceeded the rated overload threshold for an extended period, indicating the motor is being asked to do more work than it can handle.

Possible Causes

  • Cutting load exceeds motor rated torque due to deep cuts or aggressive feeds
  • Axis mechanical drag from worn ball screw, guide, or thrust bearing
  • Motor cooling fan failed or air flow blocked causing thermal buildup
  • Motor winding insulation degraded causing partial short between phases
  • Drive current sensing circuit drifted, reporting false overload

Troubleshooting Steps

  1. Step 1: Identify the affected axis and reduce the cutting load
    Axis alarm clears after reducing feed rate or depth of cut
  2. Step 2: Check the motor temperature by touch or infrared thermometer
    Motor surface temperature below 80C (176F)
  3. Step 3: Inspect the motor cooling fan for free rotation and air flow
    Fan spins freely, air flow is unobstructed
  4. Step 4: Check for mechanical drag by jogging the axis with the motor disabled
    Axis moves freely by hand with consistent resistance
  5. Step 5: If motor is overheating without load, check winding resistance
    Phase-to-phase resistance balanced within 5% of nameplate values

How to Reset

To reset: 1) Reduce the cutting load or fix the mechanical drag. 2) Allow the motor to cool. 3) Press RESET on the control. Caution: Repeated overload trips will damage the motor insulation. Investigate the root cause before resuming production.

Frequently Asked Questions

  • Q: What causes a servo motor to overload?

    Overload occurs when the motor draws more current than its rated capacity for too long. Common causes include excessive cutting loads, mechanical drag (worn ball screw or guide), failed cooling fan, or winding degradation.

  • Q: Can I increase the overload limit to prevent the alarm?

    No. The overload protection exists to prevent motor damage. Instead, reduce the cutting parameters, fix mechanical issues, or upgrade to a larger motor if the application consistently exceeds the rated capacity.

Related Haas Fault Codes

Source: Haas Automation Operator's Manual - Alarm Codes, 2023

Category: CNC