Siemens SINUMERIK codes
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Siemens SINUMERIK Controller

Spindle · Intermediate · 30-120 minutes

Alarm 21701

Siemens 840D 21701 - Channel block axis measurement not possible

Alarm 21701 fires when the SINUMERIK 840D NCK detects an invalid parameter or configuration in a Level 2 measurement task (MEASA, MEAWA, MEAC). This occurs because the programmed measurement mode, probe assignment, encoder reference, or measurement signal edge configuration conflicts with system capabilities or MD/SD parameter settings.

Siemens SINUMERIKSpindleIntermediate30-120 minutes

21701

Siemens 840D 21701 - Channel block axis measurement not possible

Channel block axis measurement not possible

Siemens SINUMERIK 840D alarm 21701: Channel block axis measurement not possible. This alarm indicates a program or channel-level error on the SINUMERIK control. The part program or machine function cannot be executed as commanded.

Root Cause Summary

Alarm 21701 fires when the SINUMERIK 840D NCK detects an invalid parameter or configuration in a Level 2 measurement task (MEASA, MEAWA, MEAC). This occurs because the programmed measurement mode, probe assignment, encoder reference, or measurement signal edge configuration conflicts with system capabilities or MD/SD parameter settings.

Safety

  • Refer to Siemens documentation
  • Ensure qualified technician performs repairs

Causes and Fixes

  1. 1

    Verify NC program syntax: confirm MEASA/MEAWA/MEAC block uses valid mode parameter (1, 2, or 3). Check that mode 2 is used if identical measurement edges are programmed.

  2. 2

    Navigate to Diagnostics > Parameters > Machine Data (MD) and verify MD 37000 = 1 (probing active) and MD 37100 series probe assignments match the probe number referenced in NC code.

    Ensure probe type in MD 37110 (0=analog, 1=digital) matches hardware configuration.

  3. 3

    Check HMI > Measurement > Probe Management to confirm probe is enabled and calibrated. Verify probe offset (MD 37130) is non-zero if mechanical offset exists.

  4. 4

    If probe recently changed, cycle power to NCK and reload tool offset data; stale probe cache may cause mode/encoder mismatch errors.

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