Study On Non-Contact Ultrasonic Polishing Mechanism Of Optical Glass And Optimization Of Polishing Process

Recently,the photoelectric industry has been developing rapidly.As one of the basic material,the ultra-precision processing of optical glass has received more and more attention.However,the hardness of the optical glass is high,while the toughness is poor,leading to crack during the processing,which will affect surface quality and production efficiency.How to improve the machining efficiency while ensuring the surface quality of optical glass is an urgent problem to be solved.With the wild application of optical glass in the fields of astronomy and laser,the requirements for processing of optical glass are developing.The optical glass has larger diameter,aspheric surface and higher precision.The work piece quality and processing efficiency are greatly affected by individual differences of workers in traditional polishing,so new polishing methods are proposed constantly.Among them,non-contact polishing has been widely concerned,like elastic emission machining and float polishing,etc.The dynamic loading between the specimen and the polishing tool is achieved in these method.Although these methods can get better surface quality,it is not suitable for complex surface polishing.In this paper,abrasives excited by ultrasonic vibration impact test specimen.Optical glass is taken as the research object to analyze the removal mechanism of the polishing process of hard and brittle materials,and the process optimization is carried out according to the analysis results.The research contents are as follows:(1)Research on the removal mechanism of hard brittle materials by non-contact ultrasonic polishing.Analyze the brittleness removal process and ductility removal process with the impacting of abrasive under the ultrasonic frequency.The results showed that in addition to the processing equipment and the inherent nature of the specimens,the parameters that may influence non-contact ultrasonic polishing removal mechanism significantly are polishing liquid concentration,abrasive particle size,ultrasonic frequency,ultrasonic amplitude and distance from the tool base to the specimen surface.(2)Factor significance test and establishment of second order regression equation.The removal mechanism of non-contact ultrasonic polishing is complicated,and it is difficult to fully explain the polishing mechanism by theoretical derivation.Single factor experiment is used to explore the effects of ultrasonic amplitude,polishing liquid concentration and the distance from the tool base to the specimen surface on material removal rate and surface roughness.Experimental results show that the three factors have significantly effects on the two responses respectively.23 factorial experiment and climbing experiment were used to find the design area including the optimal point.The response surface method is used to further explore the relationship between factors and responses,and the second-order regression models are concluded.(3)Optimize the process parameters.Draw the response surface with the second-order regression models,and draw the corresponding process diagram to guide the process.When the ultrasonic amplitude is 7.96μm,the concentration of polishing fluid is 223.7g/l,and the distance from the tool base to the machined surface is 2.67mm,the optimal theoretical roughness value is obtained as Ra3.41nm.The optimal theoretical material removal rate is obtained as 48.50nm/min when the ultrasonic amplitude is 8 um,the concentration of polishing solution is 233.01g/l and the distance from the tool base to the machined surface is 2.16mm.The relative error between the optimization results and the experimental results is less than 15%.