Reasearch On Detection And Correction Method For Surface Shape Of Pitch Lap In Continuous Polishing

Ultra-precision planar optics are widely used in laser inertial fusion restraints,astronomical telescopes,strong laser weapons,biomedical imaging and inspection.Continuous polishing is the main method for processing large-diameter ultra-precision planar optical components and is widely used in industry.In the continuous polishing process,the asphalt polishing pad is the main processing tool of ultra-precision planar optical components,and the surface shape accuracy directly affects the processing precision of the components.However,due to the shape error of the polishing pad and the surface of the component,and the super elastic and viscoelastic material characteristics of the polishing pad,the stress and strain at the interface between the component and the polishing pad have a remarkable non-uniform distribution characteristic,which greatly affects the surface accuracy of the component.In this paper,the surface shape of the polishing pad was tested to determine the actual surface shape of the polishing pad in the polishing process.Based on the actual shape of the polishing pad,the surface shape correction method of the polishing pad was studied.The surface of the polishing pad was analyzed from the aspects of full aperture and sub-calibre correction.The material removal characteristics are used to determine the method of adjusting the relevant correction parameters of the correction pad and the partial correction of the small tool to improve the surface shape accuracy of the polishing pad.The main research contents of this paper are as follows:1.Determining the method of detecting the surface shape of the polishing pad.The systematic errors existing in the detection method are analyzed from the experimental guide rail,the rotating shaft of the polishing pad,the inclination of the pad surface,etc.,and the corresponding errors are corrected and compensated.Meanwhile,a new method for linearity error detection of the machine tool guide is proposed,and the feasibility of the method is verified by experiments.Finally,the actual surface shape of the polishing pad is measured by experiments.2.The research on the evolution law of the shape of the polishing pad under the correction pad is carried out.A contact model between the polishing pad and the correction pad surface is established,and the stress distribution of the contact area on the surface of the polishing pad is simulated and analyzed;the kinematic model of the polishing pad and the correction pad is established,and the relative movement speed of the polishing pad and the correction pad is calculated.Based on the Preston equation,combined with the simulation results,the distribution of material removal on the surface of the polishing pad under the correction pad is calculated.According to the actual surface shape of the polishing pad,the influence of the correction on the material removal rate of the polishing pad under different correction parameters(correction pad-polishing pad center distance,correction pressure,polishing pad-correction pad rotation ratio)is simulated and analyzed,and the evolution of the surface shape of the pad is also analyzed.Finally,the correctness of the simulation results is verified by experiments.3.A method for correcting the surface shape error of a polishing pad based on a small tool is studied.The material removal model of the tool and polishing pad is established,and the MRR and the material removal amount distribution of polishing pad in the tool correction area is calculated.The tool modification experiment was designed to compare the surface shape of the polishing pad before and after the correction of the small tool.The experimental results show that the small tool can effectively reduce the surface shape error of the polishing pad.On this basis,through the analysis of the correction pad and the small tool correction method,it is found that the two methods have significant effect in removing the surface taper error and flatness error of the polishing pad respectively,and the correction method of combining the correction pad and the small tool is summarized.