High-efficiency Precision Grinding Of Ceramic Moulds For Cylindrical Microlens Arrays

Aimed at the present problems in the machining of cylindrical microlens array molding dies,which include low processing efficiency,the non-universal ground surface model,and less research on the removal mechanism of ceramic materials and the prediction of the surface topography,the dissertation focused on the micro-abrasive water jet(MAWJ)precision dressing of the textured grinding wheel and the high-efficient precision grinding of the RB-SiC moulds.A dwell time solution algorithm for MAWJ dressing was proposed.The dressing experiment of the diamond wheel reveals the dressing mechanism of the MAWJ.The nano-indentation experiment was used to study the removal mechanism of the phases of the RB-SiC materials.The prediction model of the surface roughness of ceramic moulds materials was established.The surface topography model of the textured grinding wheel was established,and the re-reflection mechanism in grinding was revealed.The differences in the mechanical behavior of the individual phase of the ceramic moulds materials were analyzed.The rough-fine integrated grinding process for ceramic moulds materials was proposed.The grinding experiments of sinusoidal cylindrical microlens arrays were carried out.The ultra-precision grinding process method was optimized to obtain high shape accuracy and the high-quality surface of moulds.Therefore,the key problems existing in the ultra-precision grinding of the micro-structure optical functional surface of ceramic moulds materials are solved,which include low processing efficiency,surface shape accuracy and difficulty in controlling the surface.The influence of single process parameters and the interaction between process parameters on removal depth and removal width were studied.The results show that the removal depth and width increase with the increase of the jet pressure,the removal width increases with the increase of the target distance,the target distance has a small effect on the removal depth,the removal depth and removal width decrease with the increase of the speed of the grinding wheel,the removal depth and removal width increase with the increase of the abrasive flow and number of processing times.The theoretical model of removal function was established.The experimental results show that the kerf geometry is described mathematically by a cosine function and appears good stability.The Tikhonov regularization algorithm was used to solve the dwell time.The edge smoothing algorithm was used to reduce the edge effect of the algorithm.The theoretical calculation was used to predict the machining results.The results of the dressing experiment show that the actual wheel profile were in agreement with the theoretical predictions.The deviation value can be controlled within 0.6%.The mechanism of the MAWJ dressing grinding wheel was studied.The material removal mode of the grinding wheel surface includes the dislodgement of the abrasive grains and the ductile removal of the binder material.The removal mechanism is different due to the different strength between diamond grains and binder.The critical depth of the brittle-ductile transition of the Si phase and SiC phase in RB-SiC were obtained.The critical depth of the brittle plastic transition of the SiC phase is lower than that of the Si phase.Pressure causes the transformation of the Si phase,which will change the brittle-ductile transition critical condition of the Si phase.It is conducive to improving the ductile grinding performance of the Si phase.The analytical surface roughness model of precision ground RB-SiC was established.The influence of process parameters on surface roughness was analyzed.The results show that the surface roughness decreases with the increase of grinding ratio in ductile region.Considering that the difference of RB-SiC material removal mechanism,the prediction error of the surface roughness model is about 5.87%,which is much smaller than that of the traditional model.It has significant application in controllable grinding of the RB-SiC.The grinding motion model of the textured grinding wheel was established.The interference traces between the effective abrasive particles and the workpiece were selected to generate a three-dimensional numerical topography of the workpiece surface.The accuracy of the theoretical model of surface topography under different grinding conditions was verified by experiments.Compared the errors between the simulated surface topography and the grinding surface topography,the results show that the simulated surface is in good agreement with the measurement results.The prediction accuracy of the contour height feature is 97.1%.The effect of tool setting error and wheel wear error on the profile accuracy of sinusoidal cylindrical microlens arrays were studied.The rough-fine integrated grinding technique was applied for machining the cylindrical microlens arrays.The surface profile error of the array is less than 6 ?m and the surface roughness is less than 0.04 ?m.Compared with the grinding wheel profile before and after rough grinding,the wear of metal-bonded and resin-bonded wheels are only 90 nm and 40 nm.It can reduce the influence of grinding wheel wear on profile accuracy.The method not only improves the quality of processing but also improves grinding efficiency.