Investigation On Wheel Wear And Process Optimization For Precision Grinding Of Fresnel Microstructured Moulds

The axis-symmetrical micro-structured optical functional elements have been widely applied in advanced optical systems,due to its superior properties in terms of light weight,miniaturization and integration.Recently,the glass-molding-press(GMP)technology has developed quickly to realize the mass replicating production of micro-structured optical elements.However,the rapid grinding wheel wear problem in the diamond grinding process for the moulds has limited the improvement of machining efficiency and accuracy.In this research,focusing on the silicon carbide(SiC)Fresnel moulds used in GMP,the wheel wear problem,optimization of wheel tip angle and grinding parameters have been investigated,in order to achieve the the high efficiently and high precision machining of Fresnel micro-structured moulds.Resin-bonded diamond V shape grinding wheels was used to grind the Fresnel micro-structured surface on SiC,the fundamental research about grinding wheel wear was conducted,followed by SEM observation to uncover the wear mode of grinding wheels.Some simulation research was performed using MATLAB,with respect to the phenomenon of residual center island,step valley angle radius and step peak angle overcut on Fresnel micro-structured surface caused by wheel wear.Through theoretical analysis and grinding experiments,the influence of wheel wear on the form accuracy and surface roughness of Fresnel micro-structured surface was analyzed.Three V shape grinding wheels with different tip angles(45°,60°,75°)were used to grind Fresnel micro-structured surface on SiC,the optimization of wheel tip angle was researched.By comparison of the wheel wear volume,material removal volume and grinding ratio in different moment of grinding process,the influence of wheel tip angle on its anti-wear performance was studied.The effect of wheel tip angle on grinding accuracy was analyzed through the form accuracy and surface roughness of Fresnel micro-structured surface machined by grinding wheels with different angles.Linear grooves' grinding experiment was used as the simplification for the grinding process of Fresnel microstructure.Single factor experiment was designed and performed to analyze the influence of grinding width and horizontal feedrate speed on workpiece surface quality.The grinding force and material removal rate at different grinding parameters were calculated,then the ratio between the two values was selected to evaluate the anti-wear performance of grinding wheel at a specific grinding parameter.Afterwards,SEM observation was used to compare the surface quality of linear grooves machined by different grinding parameters and the optimal grinding parameter was obtained.Using the optimized grinding parameter to machine Fresnel micro-structured surface on SiC,the desired precision criterion of Fresnel moulds was reached,with surface roughness Ra below 10 nm and form error below 1 ?m.It proved that the machining accuracy of Fresnel micro-structured moulds was improved successfully through the research of wheel wear and process optimization.