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Siemens SINUMERIK Controller
Servo/Axis · Intermediate · 30-120 minutes
Siemens 27104 - Axis difference in function safe cam plus , NCK: drive:
Alarm 27104 indicates a cross-channel comparison failure between NCK and drive safety monitoring in the SafeCAM Plus function, where the dual-channel monitoring bits (result list 2) show discrepancy. This safety-critical alarm prevents axis motion until the monitoring channels are synchronized and the fault is resolved.
27104
Siemens 27104 - Axis difference in function safe cam plus , NCK: drive:
Axis difference in function safe cam plus, NCK: drive
During cross-comparison of result list 2 ("Safe cams" function) and result list 3/4/5/6/7 ("Safe cam track" function), the status of safe cam plus monitoring was found to be different in the NCK and drive monitoring channels. The following applies to the "Safe cams" function: - Safe cam 1+: bit 0, 1 in result list 2 - Safe cam 2+: bit 4, 5 in result list 2 - Safe cam 3+: bit 8, 9 in result list 2 - Safe cam 4+: bit 12,13 in result list 2 The following applies to the "Safe cam track" function: (each of result lists 3-7 contains 6 cam results) - Safe cam 1+: bit 0, 1 in result list 3 - Safe cam 2+: bit 4, 5 in result list 3 - Safe cam 3+: bit 8, 9 in result list 3 - Safe cam 4+: bit 12,13 in result list 3 - Safe cam 5+: bit 16,17 in result list 3 - Safe cam 6+: bit 20,21 in result list 3 - Safe cam 7+: bit 0, 1 in result list 4 - Safe cam 8+: bit 4, 5 in result list 4 - Safe cam 9+: bit 8, 9 in result list 4 - Safe cam 10+: bit 12,13 in result list 4 - Safe cam 11+: bit 16,17 in result list 4 - Safe cam 12+: bit 20,21 in result list 4 - Safe cam 13+: bit 0, 1 in result list 5 - Safe cam 14+: bit 4, 5 in result list 5 - Safe cam 15+: bit 8, 9 in result list 5 - Safe cam 16+: bit 12,13 in result list 5 - Safe cam 17+: bit 16,17 in result list 5 - Safe cam 18+: bit 20,21 in result list 5 - Safe cam 19+: bit 0, 1 in result list 6 - Safe cam 20+: bit 4, 5 in result list 6 - Safe cam 21+: bit 8, 9 in result list 6 - Safe cam 22+: bit 12,13 in result list 6 - Safe cam 23+: bit 16,17 in result list 6 - Safe cam 24+: bit 20,21 in result list 6 - Safe cam 25+: bit 0, 1 in result list 7 - Safe cam 26+: bit 4, 5 in result list 7 - Safe cam 27+: bit 8, 9 in result list 7 - Safe cam 28+: bit 12,13 in result list 7 - Safe cam 29+: bit 16,17 in result list 7 - Safe cam 30+: bit 20,21 in result list 7 Monitoring status (,): - OFF = Monitoring is inactive in this monitoring channel - OK = Monitoring is active in this monitoring channel, limit values are not violated - L+ = Monitoring is active in this monitoring channel, upper limit exceeded - L- = Monitoring is active in this monitoring channel, lower limit exceeded Alarms Control reaction: NC Start disable in this channel. Alarm display. A Stop F was triggered. If safe monitoring was active, STOP B was also triggered automatically. In this case, a power OFF/ON of the control will be required.
Root Cause Summary
Alarm 27104 indicates a cross-channel comparison failure between NCK and drive safety monitoring in the SafeCAM Plus function, where the dual-channel monitoring bits (result list 2) show discrepancy. This safety-critical alarm prevents axis motion until the monitoring channels are synchronized and the fault is resolved.
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 > Alarms menu and note the axis number and specific SafeCAM index (%2 parameter). Cross-reference bit positions in result list 2 to identify which SafeCAM (1+, 2+, 3+, or 4+) triggered the alarm.
- 2
In NCK menu, navigate to Axis > [Axis Name] > SafeCAM and verify SafeCAM Plus parameters (MD 36700-36730 range) match between NCK and drive. Check MD 36703 (SafeCAM enable), MD 36706 (SafeCAM hysteresis), and MD 36720 (SafeCAM speed threshold).
Do not modify SafeCAM parameters while axis is in motion or during operation.
- 3
Check encoder signal integrity: oscilloscope test of encoder A/B/Z signals on the affected axis. Look for signal jitter, missing pulses, or EMI coupling on the encoder cable. SafeCAM Plus uses encoder feedback for cam crossing detection; poor signal quality causes NCK-drive comparison errors.
High-frequency noise on encoder lines can cause intermittent SafeCAM monitoring faults.
- 4
Clear the alarm and perform a 5-cycle test moving the axis through the SafeCAM zone at controlled speed (MD 36705 SafeCAM speed range recommended). Monitor Trace > SafeCAM status bits in real-time. If alarm reoccurs at same position, the issue is reproducible and requires hardware replacement (encoder or safety module).
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