What causes Siemens SINUMERIK alarm 16781?

Part program contains an illegal or unsupported command for the current machine configuration. Channel or axis configuration does not support the programmed function. Required machine option not enabled for the commanded function. Axis assignment or transformation configuration error. Program execution sequence error.

How do I fix Siemens SINUMERIK alarm 16781?

1. Identify the program block that triggered the alarm — note the channel and block number. 2. Review the commanded function against the SINUMERIK programming manual. 3. Check if the required machine option is enabled for this function. 4. Verify axis assignments and transformation settings are correct for the application. 5. Consult the Siemens SINUMERIK alarm manual for alarm 16781 specific remedy.

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Siemens SINUMERIK Controller

Spindle · Intermediate · 30-120 minutes

Alarm 16781

Siemens 840D 16781 - Channel block master spindle/axis missing

SINUMERIK alarm 16781 fires when a synchronous spindle function (SPOS, SPOSA, M19, or gear spindle positioning) is commanded without a master spindle/axis being defined in the part program. The NCK requires explicit master spindle declaration via G-code syntax or machine parameter configuration before any master-dependent operations can execute.

Siemens SINUMERIKSpindleIntermediate30-120 minutes

16781

Siemens 840D 16781 - Channel block master spindle/axis missing

Channel block master spindle/axis missing

Root Cause Summary

SINUMERIK alarm 16781 fires when a synchronous spindle function (SPOS, SPOSA, M19, or gear spindle positioning) is commanded without a master spindle/axis being defined in the part program. The NCK requires explicit master spindle declaration via G-code syntax or machine parameter configuration before any master-dependent operations can execute.

Safety

Refer to Siemens documentation
Ensure qualified technician performs repairs

Causes and Fixes

1
Review the NC part program at the block referenced in the alarm (%2). Locate the SPOS, SPOSA, M19, or spindle-synchronized command that triggered the alarm.
2
Insert SETMS(S1) or SETMS(S2) command before the spindle synchronous operation. Example: N10 SETMS(S1) / N20 SPOS=0 / N30 G04 F0.5. Verify spindle identifier matches configured spindle name in MD10050 (Spindle names).
SETMS must be declared in the same or preceding block; it does not persist across program segments unless in a subroutine context.
3
Check machine parameter MD10050 (Spindle names) and MD10051 (Spindle types) via HMI → Diagnosis → Parameters → Machine Data. Confirm the spindle referenced in SETMS(S1/S2) exists and is configured as type 1 (Main spindle) or type 2 (Sub-spindle).
4
If using spindle orientation cycles (M19, G65 positioning), verify MD20090 (Spindle synchronous function) is enabled (bit 0 = 1) and MD20100 (Master spindle for synchronous operation) specifies a valid spindle number (typically 1).

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