Haas NGC 3.108 AXIS SERVO OVERLOAD on Z-axis during heavy cut, what to check?
I'm getting a 3.108 AXIS SERVO OVERLOAD alarm on my Haas NGC lathe's Z-axis. It happens during heavy cuts, and I've noticed the Z-axis load meter stays high throughout the pass. What should I check first?
Alarm 108 AXIS SERVO OVERLOAD on a Haas NGC means an axis motor sustained a load over 100% for an extended period. The prefix '3.' indicates the Z-axis. This alarm is distinct from a servo error (103) where the axis cannot reach its commanded position, or a user-set tool load limit (174). The control's Axis Overload Timer starts counting down when the load reaches 180%, triggering the alarm if it hits zero.
Likely causes and checks
1Feeds and speeds too high for the cut
- Points to it
- The most common cause for a sustained high axis load during heavy cutting is that the programmed feeds and speeds are too aggressive for the material or tool.
- Check
- Reduce the feeds and speeds in your program and monitor the Z-axis load in the position display during the cut. If the load drops and the alarm clears, this was the issue.
2Dull or broken tool
- Points to it
- A worn or damaged tool requires more force to cut, leading to increased axis motor load. This often manifests as the load rising over the tool's life or an alarm appearing after a tool chips.
- Check
- Inspect the cutting tool for any signs of wear, chipping, or breakage. Replace the tool if it appears dull or damaged.
3Mechanical blockage or binding in the axis
- Points to it
- Physical obstructions or binding within the Z-axis's path of travel can cause the motor to work harder, leading to an overload. This can include chips in way covers or issues with the axis's linear guides.
- Check
- Ensure the Z-axis has a clear path of travel. Look for any chips or debris that might be accumulating in the way covers or obstructing movement. Jog the axis and listen for unusual noises.
4Brake not releasing
- Points to it
- If the Z-axis motor brake is not fully releasing, it will create constant drag, causing the motor to operate under a high load even during commanded moves.
- Check
- On linear axes, check for 20–30 VDC across the brake leads after pressing RESET. There should be no voltage across the leads when the machine is in E-stop.
Next check: Given that the alarm occurs during heavy cuts and the axis load meter is high, start by reducing the feeds and speeds in your program and observing the Z-axis load. If that doesn't resolve it, inspect your cutting tool for wear or damage.
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