Analysis of TC_INNEST Alarm on FANUC M-900iA Multigun Welding Robot System

English

Abstract

Industrial welding robots are critical assets in automotive manufacturing, where high system reliability is essential to maintain production continuity and minimize downtime. This study investigates the recurring TC_INNEST alarm in a FANUC M-900iA multigun welding robot equipped with dual welding guns. The alarm consistently occurred during the automatic gun-changing sequence, particularly when the robot returned to the home position after releasing the first welding gun and before engaging the second gun. Field observations showed that the alarm occurred more than 10 times per production shift, resulting in approximately 1–3 minutes of downtime per occurrence. Based on direct field observations, technical inspections, and maintenance analysis, the alarm was associated with communication instability and interlock disturbances involving the DeviceNet communication system, communication cables, sola cables, and the robot controller. Initial corrective actions, including controller reset and temporary plug-and-play reconnection, restored robot operation but failed to eliminate the root cause. Comprehensive corrective maintenance, including communication cable replacement, controller inspection, motherboard cleaning, and replacement of internal communication cables, successfully eliminated the recurring alarm. The findings indicate that degradation of communication components and contamination inside the controller significantly affected communication reliability during the automatic tool-changing process. Overall, no recurrence of the TC_INNEST alarm was observed during subsequent production, demonstrating the effectiveness of the proposed maintenance strategy for improving robot reliability and reducing production downtime.