Research on ultrasonic grinding ZrO₂ ball valve with a cup-shaped diamond grinding wheel

To achieve high efficiency and low damage processing of ZrO₂ ceramic ball valves, a method for the cup-shaped composite grinding wheel of ultrasonic vibration grinding system was proposed. Based on Mindlin’s thick plate theory and cylinder longitudinal vibration theory, a cup-shaped composite grinding wheel including the stepped rod and cup tool head was designed. The theoretical error is within 4%. The influence of the length of the small end of the stepped rod and the diameter of the grinding wheel on the resonance frequency and ultrasonic amplitude was explored by the finite element method (FEM), and the structural parameters of the cup-shaped composite grinding wheel were optimized. The prototype verified that the error between the resonant frequency and the design frequency of the two kinds of cup-shaped composite grinding wheels after matching with the transducer was within 2%, and the maximum amplitude stable output was up to 8 μm. The ultrasonic grinding experiment of the ZrO₂ ceramic ball valves was carried out. The results showed that ultrasonic grinding reduced the maximum height difference of the workpiece surface, reduced by 28% compared with conventional grinding (CG). The surface roughness was reduced to meet the actual processing requirements. The edges of the workpiece appeared serrated structure and micro-crushing phenomenon compared with CG, which may involve from low stiffness and suitable grinding parameters, especially the rotation speed limit of the fourth axis used for the workpiece rotation.