Automotive assembly line operators face prolonged exposure to the human-machine interfaces (HMIs) of intelligent equipment. High-frequency visual searches and cognitive judgments easily lead to fatigue accumulation

resulting in increased error rates. This study proposes a fatigue-prevention optimization scheme without additional hardware investment

comprising three core designs: a status-sensitive display mechanism based on work process flow

a sliding key confirmation interaction

and a grayscale micro-rest mode integrated into the production rhythm. Application verification on sixteen workstations in a certain automotive assembly workshop shows that after optimization

the visual fatigue self-assessment score decreased by approximately 40%

the process rework rate decreased by more than 50%

pupil dilation amplitude decreased by 31%

and the gaze drift frequency decreased from twelve times per minute to six times per minute. This study confirms the effectiveness of alleviating fatigue in industrial settings by addressing human-machine interaction logic and provides a practical technical reference for interface design in high-paced mixed-line production environments.