Research On Grinding Mechanism Of Elliptical Ultrasonic Assisted Diamond Grinding Wheel For K9 Glass

Optical glass is widely used because of its low density,high hardness,low coefficient of thermal expansion,wear resistance and stable chemical properties.Special K9 glass is mainly used in large volume prism,high-end projection lens in digital projection system and highresolution lens in professional camera due to its high transmittance and low dispersion.However,it is difficult to manufacture because of its low fracture toughness and high hardness.Although precision molding technology has been applied to the processing of glass,the processing method is not only high cost,but also its maximum molding size is restricted by the existence of thermal expansion coefficient.Nowadays,grinding and polishing are always the most effective processing methods in the processing of large mirror and general optical manufacturing enterprises.Milling,fine grinding,polishing and corresponding auxiliary work accounted for 50%of the working hours.However,brittle parts are prone to deformation layer,surface or subsurface crack,phase transformation,residual stress and other forms of damage during grinding.These damages may seriously affect the surface properties of brittle materials,resulting in a serious reduction in strength or even failure.Therefore,in order to improve the processing efficiency of K9 glass and ensure high surface quality,ultrahigh precision and low subsurface damage,two-dimensional ultrasonic assisted grinding was introduced into the processing technology of optical glass.In this project,elliptical ultrasonic vibration assisted grinding technology was introduced into K9 glass processing system.Starting from the kinematics characteristics of elliptical ultrasonic vibration assisted grinding and the removal mechanism of K9 glass,the grinding force,workpiece surface morphology,and abrasive wear were studied.The specific research contents of this paper are as follows:(1)The trajectory of a single abrasive relative to the workpiece under the condition of elliptical ultrasonic vibration was studied,and the kinematic equation of the abrasive was established.The contact rate models of abrasive and workpiece in feed direction and cutting depth direction were established respectively,and the contact time of abrasive and workpiece is analyzed.The influence of process parameters and vibration parameters on contact rate was also analyzed.(2)The typical surface characteristics of K9 optical glass in the case of single abrasive scoring and grinding were studied.Based on the contact rate,model and brittleness removal mechanism,the mathematical model of normal force in elliptical ultrasonic assisted side grinding was established.The effects of process parameters and vibration parameters on normal force were discussed through experimental verification and theoretical analysis.(3)The surface quality of K9 glass under elliptical ultrasonic assisted grinding was studied.Based on the kinematic equation and the critical depth of brittleness removal,the simulation model of workpiece surface was established.Through the face grinding experiment and side face grinding experiment,the influence of various process parameters on the workpiece surface roughness was analyzed.(4)The abrasive ware under the synergistic effect of micro lubrication and ultrasonic assisted grinding was studied.The experimental results show that the micro lubrication technology can effectively solve the problem of abrasive blocking,improve the service life of abrasive.