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Siemens SINUMERIK Controller
Servo/Axis · Intermediate · 30-120 minutes
Siemens 300745 - Axis drive limit values for safe end positions exchanged
This alarm occurs when the safe end position limit values in the machine data (MD) are incorrectly set, with the upper limit lower than the lower limit. Fix by correcting the MD values during control boot-up.
300745
Siemens 300745 - Axis drive limit values for safe end positions exchanged
Axis drive limit values for safe end positions exchanged
For the safe end position monitoring, there is a smaller value in the MD for the upper limit value than in the MD for the lower limit value. Request: During boot-up of the control Control reaction: Mode group not ready. Channel not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm.
Root Cause Summary
This alarm occurs when the safe end position limit values in the machine data (MD) are incorrectly set, with the upper limit lower than the lower limit. Fix by correcting the MD values during control boot-up.
Safety
- Drive/power/encoder circuit: hazardous voltages may remain in the DC link after power-off. Lock out / tag out, wait for discharge per the drive documentation, and use qualified personnel only.
Causes and Fixes
- 1
SAFETY: Power Down and Lock Out
Follow LOTO procedures. Ensure machine is in safe state before accessing machine data.
- 2
Access Machine Data
Navigate to the machine data settings in the Siemens control system. Verify you have proper authorization level.
- 3
Identify Specific MD Parameters
Locate MD36100 (software limit switch minus) and MD36110 (software limit switch plus) for the affected axis.
- 4
Verify and Correct Limit Values
Ensure MD36100 < MD36110. Check against machine mechanical limits and reference point position.
- 5
Save and Validate
Save changes, perform control reboot, and verify alarm clears. Test axis movement within safe limits.
Call a technician if:
- ·If you lack proper authorization level for MD access
- ·If machine specifications are unclear or unavailable
- ·If alarm persists after correcting MD values
- ·If you are unfamiliar with LOTO procedures
- ·Before making any MD changes if unsure of correct values
Prevention
- Always backup MD before changes
- Verify values against machine documentation
- Use parameter comparison tools when available
- Document all MD changes with approval
Common Mistakes
- Overlooking upper/lower limit logic
- Failing to reboot after MD updates
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