Research On Surface Polishing Creation And Surface Morphology Of Optical Element

With the development of industry,the demand for high-precision optical components in the areas of national defense and livelihood is increasing rapidly.The last and most important process in the processing of high-precision optical components is mostly the fine polishing process.Completely replacing the traditional low-efficiency manual polishing method with the automatic polishing methods need to increase the certainty of computer polishing to improve surface form accuracy and the surface quality after computer polishing.The improvement of surface quality requires not only the control of the surface roughness of the workpiece,but also strictly control the Midspatial Frequency Errors on the surface of the workpiece.Establishing an accurate surface topography simulation model is an important prerequisite for achieving the above goals.Based on Preston equation,this paper analyzes the material removal process in the polishing process for five-axis CNC machine tool,and calibrates the coefficients of the Preston equation through experiments of polishing K9 glass.The established TIF model can be used to determine the appropriate polishing process parameters.A discrete material removal calculation model-TIF unit superposition method-is proposed.This method is more efficient than the integral solving method and it has strong applicability which can be applied to calculate the material removal profile of different polishing paths.Taking the traditional raster path and the relatively random cycloid polishing path as examples,the proposed algorithm is used to simulate the material removal profile,and the influence of process parameters such as the track interval on the material removal contour is analyzed.In addition to the polishing trajectory,another important parameter in the polishing process is the dwell time.The current solution methods for the residence time mostly include the convolution operation,which has the principle mathematical defect and the result is nonconvergence sometimes.This paper combines the TIF unit method and Tikhonov regularization method to rapidly solve the dwell time using the idea of discretization.Taking the grating trajectory and cycloid trajectory as examples to solve the dwell time of the random rough surface generated by the computer.Then the TIF element superposition method is used to calculate the material removal profile under the corresponding conditions.Then compare the surface form accuracy of the simulation results,and perform power spectral density(PSD)analysis on the material removal profile to extract Mid-spatial frequency part in the surface errors.The simulation results show that by using the discrete residence time solution method to correct the polishing creation,the Peak-to-Valley value,Root Mean Square of the workpiece surface can be improved.And it also shows that the cycloid trajectory can suppress the Mid-spatial Frequency Errors of the workpiece surface better than the raster trajectory.Finally,corresponding polishing experiments were designed and carried out to verify the effectiveness of the established polishing material removal profile model,the dwell time calculation method and the surface quality analysis.