Code 330-005B: MC safety doors are open
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical MC safety doors are open 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
[Cause of error] Guard doors are open The guard doors have to be closed in order to conduct the safety self-test or the brake test of an axis. Further possible causes: - Faulty wiring of guard doors - Guard door contact is defective - SPLC interface signal PP_AxGrpStateReq unequal to S_STATE_AUTO [10] [Error correction] - Close the guard doors in order to conduct the safety selftest or the brake test Further possible measures: - Check the wiring of the guard door contacts - Check the guard door contact. - Check the SPLC program. - Inform your service agency
Source: HEIDENHAIN NC Error Messages — TNC7/640/620/320/128, CNC PILOT 640, MANUALplus 620 (10/2023)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Heidenhain TNC Series CNC Alarms
Heidenhain controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 330-005B on the TNC Series CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Heidenhain's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4497 Heidenhain TNC Series CNC codes.
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