Code 187: B or TT Servo Error Too Large
Issue Description & Safety Warning
The Haas VF-Series CNC has triggered a critical B or TT Servo Error Too Large alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Too much load or speed on B or TT axis motor. The difference between the motor position and the commanded position has exceeded a parameter. The motor may also be stalled, disconnected, or the driver failed. The servos will be turned off and a RESET must be done to restart. This alarm can be caused by problems with the driver, motor, or the slide being run into the mechanical stops. On machines with servo based tool changer chains the chain was unable to move. On machines with servo based tool changer arms the arm was unable to move possibly due to a stuck tool.
Source: Haas VF-Series Service Manual (96-8100 rev G, 2003)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Haas VF-Series CNC Alarms
Haas controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 187 on the VF-Series CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Haas's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 461 Haas VF-Series CNC codes.
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