What causes Siemens SINUMERIK alarm 61816?

Machine powered on but reference return not completed for all required axes. Reference return interrupted before all axes homed. Absolute encoder position data lost — battery failure or encoder disconnection. Specific axes required by the called function have not been referenced. Reference point tolerance zone in machine data set too tightly.

How do I fix Siemens SINUMERIK alarm 61816?

1. Perform a complete reference return for all machine axes. 2. Verify each axis reaches its reference point indicator before proceeding. 3. Check encoder backup battery voltage if absolute position was unexpectedly lost. 4. If only specific axes show the error, home those axes individually first. 5. Check reference point tolerance parameters in machine data if homing completes but the error persists.

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Siemens SINUMERIK Controller

Servo/Axis · Intermediate · 30-120 minutes

Alarm 61816

Siemens 840D 61816 - Channel Block: Axes not on reference point

Alarm 61816 indicates that one or more axes in the specified channel have not completed machine homing (reference point approach) before executing a block that requires axis position knowledge. This is a safety-critical alarm on SINUMERIK 840D systems, as NCK cannot guarantee accurate positioning without valid reference point data stored in axis parameters.

Siemens SINUMERIKServo/AxisIntermediate30-120 minutes

61816

Siemens 840D 61816 - Channel Block: Axes not on reference point

Channel Block: Axes not on reference point

Root Cause Summary

Alarm 61816 indicates that one or more axes in the specified channel have not completed machine homing (reference point approach) before executing a block that requires axis position knowledge. This is a safety-critical alarm on SINUMERIK 840D systems, as NCK cannot guarantee accurate positioning without valid reference point data stored in axis parameters.

Safety

Refer to Siemens documentation
Ensure qualified technician performs repairs

Causes and Fixes

1
Access Diagnostics menu in NCK (HMI: Diagnostics > Axis > Reference Point Status) and verify reference point validity for each axis in the channel. Check if REF_POS_VALID or equivalent status shows FALSE.
Do not bypass homing; loss of reference data risks tool/workpiece collision.
2
Execute full machine homing cycle: issue G74 command (or manufacturer homing block) for all axes in the affected channel. Monitor Diagnostics > Axis until reference point status displays TRUE for all axes.
Ensure machine is in safe position and all protective devices are active before homing.
3
Verify homing parameters: check MD10200 (Reference point approach speed), MD10201 (Reference point approach type), and axis-specific MD10000+ (Axis enable) in Settings > Machine Data. Confirm values match machine documentation.
4
Resume NC program from block %2 after successful homing. If alarm persists, check event log (Diagnostics > Alarms > History) for preceding hardware or encoder errors that may have invalidated reference data.

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