Investigation on ultra-precision machining of eccentric shaft by applying UEVC

The eccentric shaft, a critical component in robotics and automation, poses substantial machining challenges due to its distinctive geometry and the high hardness and low fracture toughness of SCM420H steel. Brittle damage, including fractures and cracks, is prone to occur during the machining, which inevitably shortens the service life of the parts and limits their subsequent applications. This study employs ultrasonic elliptical vibration cutting (UEVC) to address these issues, developing kinematic and mathematical models to characterize tool-workpiece interaction and material removal. The model is validated by a high correlation between predictions and experiments (coefficient of determination R² = 0.944, mean relative deviation = 6.39 %). A comparative experiment between traditional grinding and UEVC was conducted, employing scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and other characterization techniques to analyze microstructural features, subsurface damage mechanisms, and material removal behavior. The results show that, compared to grinding, UEVC reduces surface roughness (Sa) by 91.7 %, improves cylindricity by 73.5 %, and achieves a 4.77 nm smooth surface. Furthermore, UEVC effectively suppresses subsurface damage, limiting the damage layer to approximately 1.46 μm, thus preventing microcrack formation, material spalling, and brittle fracture typical of grinding. These findings underscore the advantages of UEVC in precision machining of eccentric components.