700051 — Alarm 700051 (Spindle direction illegal) Diagnostic Tree

This alarm code (700051) is not found in the standard Siemens source manuals; 70xxxx series alarms are typically machine builder (OEM) specific PLC alarms (the 'Spindle direction illegal' message indicates the spindle is commanded to rotate in a direction not permitted for the current operation or tool). Please check the spindle rotation commands (M3, M4) in the NC program to verify they match the operation requirements.