Code 6417: [TO unit %1: ] Tool %2 with tool edge no. %3 has reached tool monitoring limit
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [TO unit %1: ] Tool %2 with tool edge no. %3 has reached tool monitoring limit 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 = TO unit %2 = Tool identifier %3 = Cutting edge number Definitions: This message informs that at least one cutting edge of the time or quantity monitored tool has reached its monitoring limit. The alarm was triggered through the OPI interface (MMC, PLC). The channel context is not defined. The TO unit was specified for this reason. Reaction: Interface signals are set. Alarm display. Remedy: For information only. The user must decide what to do. Program Continuation: Clear alarm with the Delete key or NC START.
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 6417 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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