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Heidenhain Controller
Safety · Intermediate · 30-120 minutes
Heidenhain 905-27E5 - Safety clearance Z
HEIDENHAIN alarm 905-27E5 'Safety clearance Z' indicates the Z-axis safety clearance distance has been violated or improperly configured. This typically occurs when the programmed Z-axis movement would result in insufficient clearance above the workpiece or fixture, triggering the TNC's collision avoidance system.
905-27E5
Heidenhain 905-27E5 - Safety clearance Z
Safety clearance Z
Heidenhain TNC error 905-27E5: Safety clearance Z. This alarm indicates a fault or error condition on the Heidenhain TNC control that requires investigation. Refer to the Heidenhain NC error message documentation for the specific cause and remedy for this alarm code.
Root Cause Summary
HEIDENHAIN alarm 905-27E5 'Safety clearance Z' indicates the Z-axis safety clearance distance has been violated or improperly configured. This typically occurs when the programmed Z-axis movement would result in insufficient clearance above the workpiece or fixture, triggering the TNC's collision avoidance system.
Safety
- Refer to Heidenhain service manual
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Check safety clearance parameter
Access MOD function → Machine Parameters → MP7440 and verify the Z-axis safety clearance value is appropriate for your setup (typically 5-20mm above highest workpiece/fixture point).
Document the original value before making changes for easy rollback if needed.
- 2
Verify current Z position
Check the actual Z position in the position display and ensure it's above the safety clearance plane defined by MP7440 plus the workpiece coordinate system Z-zero.
Never manually move Z-axis downward without confirming clearance - risk of collision.
- 3
Test safety clearance
Perform a controlled G0 Z movement to the safety clearance position in MDI mode to verify the parameter change resolves the alarm condition.
Call a technician if:
- ·Parameter changes don't resolve alarm
- ·Mechanical binding detected in Z-axis
- ·Encoder feedback errors present
Prevention
- Always verify workpiece setup height before programming
- Regularly calibrate tool lengths
- Document safety clearance settings for different setups
Common Mistakes
- Setting safety clearance too low for tall fixtures
- Forgetting to update presets after workpiece changes
- Using incorrect tool length values
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