Siemens SINUMERIK codes
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Siemens SINUMERIK Controller

Program/G-code · Intermediate · 30-120 minutes

Alarm 401805

Siemens 840D 401805 - Impermissible axis no. parameter in FC 18

Siemens SINUMERIK alarm 401805: Impermissible axis no. parameter in FC 18. An impermissible or invalid parameter was passed to PLC function block FC18. This indicates a PLC programming error or configuration mismatch in the machine tool builder ladder program.

Siemens SINUMERIKProgram/G-codeIntermediate30-120 minutes

401805

Siemens 840D 401805 - Impermissible axis no. parameter in FC 18

Impermissible axis no. parameter in FC 18

Siemens SINUMERIK alarm 401805: Impermissible axis no. parameter in FC 18. An impermissible or invalid parameter was passed to PLC function block FC18. This indicates a PLC programming error or configuration mismatch in the machine tool builder ladder program.

Safety

  • Refer to Siemens documentation
  • Ensure qualified technician performs repairs

Common Causes

  • Invalid axis number passed to FC18 in the PLC program
  • FC18 called with a parameter that exceeds the valid range for this SINUMERIK configuration
  • PLC program version mismatch — FC18 call parameters not updated after a machine configuration change
  • Number of configured axes in SINUMERIK does not match the FC18 parameter
  • PLC program downloaded with incorrect machine data for this specific machine tool

Troubleshooting Steps

  1. 1Check the SINUMERIK PLC alarm details for the specific parameter value that caused the error.
  2. 2Review the PLC program — find the call to FC18 and verify the parameter values are within valid range.
  3. 3Compare the FC18 parameter against the actual number of configured axes in the SINUMERIK machine data.
  4. 4If the PLC program was recently modified or the machine configuration changed, verify FC18 calls were updated accordingly.
  5. 5Contact the machine tool builder if the PLC program source is not available for review.

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