Haas Alarm 108 “SERVO OVERLOAD” means the axis servo load exceeded the allowed limit. On NGC controls, Haas documents that many older Classic Haas Control (CHC) servo overload alarms are consolidated into the 108 alarm group, differentiated by axis designation. oai_citation:7‡haascnc.com
What Alarm 108 Usually Means
- The axis motor is demanding too much torque to follow motion.
- The control stops to protect the drive/motor and mechanics.
The Three Real Root Cause Buckets
1) Cutting/process overload (most common on mills)
- Too aggressive feed/stepdown/stepover
- Dull tool or wrong tool geometry for material
- Chip packing causing sudden load spikes
2) Mechanical binding (common when it “appears out of nowhere”)
- Chips/debris in ways, way covers, or around ballscrew
- Poor lubrication delivery (metering issues)
- Crash damage: bent screw, damaged coupler, thrust bearing issues
3) Brake/hold hardware issues (more common on lathes / certain axes)
- Haas notes that servo brake disengagement and required 24VDC can be relevant on some configurations (especially where a brake must release for motion). oai_citation:8‡helmancnc.com
Immediate Fix (Safe Shop Procedure)
1) Stop and clear the tool from the part (avoid repeated overload cuts).
2) Reduce feed override and rerun the motion in air to confirm whether overload is process-related.
3) If it overloads even in air:
- Inspect for binding and chips
- Verify lubrication is functioning
- Check for heat/noise in the axis area
4) If it happens only under load: - Reduce stepdown/stepover
- Improve chip evacuation/coolant
- Use constant-engagement toolpaths (adaptive/trochoidal) instead of corner-loading moves
Prevention (What Pros Do)
- Set conservative entry moves and avoid full-width engagement in hard materials.
- Use CAM strategies that keep constant tool engagement.
- Don’t ignore early “load trending up” signs—108 is often the final protective stop after the load has been rising for a while.
- Maintain way cover cleanliness and lubrication schedules.
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