axismd.ai
Siemens SINUMERIK Controller
Servo/Axis · Intermediate · 30-120 minutes
Siemens 27111 - Axis fault during encoder evaluation of the safe actual value.
Alarm 27111 indicates a mismatch between the redundantly calculated safe actual value (from dual-channel encoder evaluation in the safety function) and the fine resolution actual value from the primary encoder channel on the specified axis. This discrepancy prevents the NCK from validating encoder integrity for safe motion monitoring.
27111
Siemens 27111 - Axis fault during encoder evaluation of the safe actual value.
Axis fault during encoder evaluation of the safe actual value.
The redundantly determined safe actual value does not match the fine resolution actual value of the same encoder Control reaction: Alarm display. In addition, a Stop F is triggered that may cause follow-up alarm 27001 with error code 0 as well as alarms 27023 and 27024. Alarm 27001 with error code 0 can be avoided by alarm reduction ($MA_SAFE_ALARM_SUPPRESS_LEVEL higher or equal to 1).
Root Cause Summary
Alarm 27111 indicates a mismatch between the redundantly calculated safe actual value (from dual-channel encoder evaluation in the safety function) and the fine resolution actual value from the primary encoder channel on the specified axis. This discrepancy prevents the NCK from validating encoder integrity for safe motion monitoring.
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
Access Diagnostics menu: Press [MENU] > Diagnostics > Actual Values > Monitor encoder channels for axis %1. Verify both encoder signal amplitudes are equal (typically 0-5V or 4-20mA depending on transducer type) and symmetric about center voltage.
Do not adjust encoder signal levels while spindle or axis is moving. Ensure machine is in E-STOP.
- 2
Check parameter MD31200 (encoder type for axis) and MD31202 (encoder supply voltage). Verify against actual encoder nameplate. If EnDat or SSI encoder, check MD31204 (baud rate) matches encoder specification. Parameter mismatch prevents correct fine-resolution evaluation.
- 3
Inspect encoder cable shielding and connector pins for corrosion, moisture, or bent contacts. Test continuity on all encoder lines using multimeter. Reseated or replaced cable should be routed separately from spindle/motor power cables to minimize EMI coupling.
Disconnect encoder connector at machine before continuity testing to avoid damaging input electronics.
- 4
Reset encoder evaluation by: NCK menu > Service > Encoder > Axis %1 > Reset Actual Value. Power-cycle the drive (full 840D controller reset). Re-home the axis with G28/G29 to re-establish safe actual value baseline. Monitor for alarm recurrence during normal jog motion.
Seeing Multiple Alarms?
Seeing another alarm with this one? Enter the code.
Get machine-aware diagnosis
AxisMD logs alarms against your actual machines, tracks patterns, and gives AI context your manual doesn't have.
Start freeWas this guide helpful?
Always verify with your machine manual or a certified technician before performing service procedures.