Study on surface roughness in ultrasonic vibration mill-grinding of hot-pressed Si₃N₄

In order to investigate the influence of machining parameters on surface roughness in ultrasonic vibration mill-grinding of hot-pressed silicon nitride, the mechanism of the ultrasonic vibration mill-grinding is analysed. Kinematic analysis of abrasive grain indicates that grains and workpiece separates periodically which is beneficial for coolant entering into grinding zone to reduce grinding temperature, so the surface quality is improved in certain extent. The theory of indentation of brittle material is used to analyse the mode of material removal. Orthogonal experiments were then carried out and machined surfaces were observed by SEM and detected by roughmeter. The detected results indicate that spindle speed has the most significant influence on surface roughness and the following are feeding speed, cutting depth and amplitude in turn. From the experimental data, an empirical formula was obtained through regression analysis. Finally, the effect of machining parameters on surface roughness is analysed.