Code 27102: Axis %1 difference in function safe velocity %2, NCK: %3 drive: %4
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical Axis %1 difference in function safe velocity %2, NCK: %3 drive: %4 alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Parameters: %1 = Axis number %2 = SG level for which the difference was determined %3 = Monitoring status safe velocity %4 = Monitoring status safe velocity Definitions: During cross-comparison of result list 1 a differ ence was detected between the NCK and drive monitoring channels in the status of safe velocity monitoring. - Safe velocity 1: Bit 6, 7 in result list 1 - Safe velocity 2: Bit 8, 9 in result list 1 - Safe velocity 3: Bit 10, 11 in result list 1 - Safe velocity 4: Bit 12, 13 in result list 1 Monitoring status (%3, %4): - OFF = Monitoring is inactive in this monitoring channel - OK = Monitoring is active in this moni toring channel, limit val ues are not violated - L+ = Monitoring is active in th is monitoring channel, upper limit exceeded - L- = Monitoring is active in this monitoring channel, lower limit exceeded Reaction: Alarm display. If a safe monitoring was active, STOP B was also triggered automat ically. In this case, a power OFF/ON of the control will be required. Remedy: Check whether the safe inputs have switched to the same status in both monitoring channels within the permissible time tolerance. For further diagnostics, the drive parameters r9710[0], r9710[1] and the servo trace signals "Result list 1 NCK" and "Result list 1 drive" can be used. Program Continuation: Clear alarm with the RESET key. Restart part program
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 27102 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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