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Haas Controller
Program/G-code · Intermediate · 20 - 60 minutes
Haas 391 - FEATURE DISABLED | Haas CNC Alarm
Haas Alarm 391 occurs when the tailstock servo fails to reach its commanded position within the tolerance specified in Parameter 334 (Position Error Limit) and the time limit set in Parameter 335 (Position Error Time). This closed-loop feedback error indicates a mismatch between the NGC controller's commanded position and the actual encoder feedback from the tailstock servo motor.
391
Haas 391 - FEATURE DISABLED | Haas CNC Alarm
FEATURE DISABLED
This alarm occurs when the control detects a G-code command or function that is not enabled in the machine configuration or has been intentionally disabled through software licensing or parameter settings. The MOCON checks the feature enable bits and licensed options when processing the program, and this alarm prevents execution of unauthorized or unavailable features. Common on machines where optional features like high-speed machining, probing, or fourth-axis control were not purchased or have been deactivated.
Root Cause Summary
Haas Alarm 391 occurs when the tailstock servo fails to reach its commanded position within the tolerance specified in Parameter 334 (Position Error Limit) and the time limit set in Parameter 335 (Position Error Time). This closed-loop feedback error indicates a mismatch between the NGC controller's commanded position and the actual encoder feedback from the tailstock servo motor.
Safety
- Part may not be supported
- WARNING: Workpiece may lack proper support
- Ensure machine is in emergency stop before performing any mechanical or electrical troubleshooting.
- Disconnect power to the machine before working on electrical components.
- Be aware of pinch points when working around the tailstock.
- Use proper lifting techniques when moving or adjusting the tailstock.
- If the tailstock is hydraulically or pneumatically powered, relieve pressure before disconnecting any lines.
- Wear appropriate personal protective equipment (PPE), including safety glasses and gloves.
- Always power off and lock out the machine before performing checks to prevent injury.
Causes and Fixes
- 1
Check tailstock ways and slides
Inspect tailstock slides for chips, debris, or damage. Clean ways with appropriate solvent and check for proper lubrication per Haas maintenance schedule.
Ensure machine is in E-STOP before manual inspection
- 2
Verify tailstock clamp operation
Check if tailstock clamp is properly releasing during positioning moves. Verify hydraulic pressure at DIAGNOSTICS > HYDRAULICS menu shows proper clamp pressure release.
Listen for clamp release sound during tailstock movement - absence indicates hydraulic issue
- 3
Inspect mechanical coupling
Check tailstock drive coupling for wear or damage. Look for excessive backlash or binding in the drive mechanism that could prevent accurate positioning.
Call a technician if:
- ·Servo motor replacement needed
- ·Drive amplifier failure confirmed
- ·Encoder replacement required
Prevention
- Regular tailstock way lubrication per Haas schedule
- Keep tailstock area clean of chips and debris
- Monitor hydraulic pressure levels weekly
Common Mistakes
- Setting position tolerance parameters too restrictively
- Ignoring hydraulic clamp release during troubleshooting
- Not checking encoder cable routing for EMI interference
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Always verify with your machine manual or a certified technician before performing service procedures.