Code 231-A950: Safely limited increment (SLI) exceeded %1
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Safely limited increment (SLI) exceeded %1 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] - The maximum permissible path was exceeded in the Safely Limited Increment (SLI) mode. - Possible causes: - The selected increment exceeds the value from the safe machine parameter distLimitJog - The drive overshoots mechanically when the limit position is reached - Drive is not optimally adjusted. [Error correction] - Enter a smaller jog increment. - Check the entry in the safe machine parameter distLimitJog. - When the jog increment end position is reached, use the control's internal oscilloscope to check the actual position value for overshooting. - Adjust the drive. - 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 231-A950 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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