Study On The Surface Shape Correction Process Of Shear Rheology Derministic Polishing

Deterministic polishing realizes the fixed-point quantitative removal of the surface material of the workpiece by controlling the removal function and residence time,which is an important means to improve the accuracy of the workpiece surface.Deterministic Shear Rheological Polishing(DSRP)is the application of Shear Rheological Polishing(SRP)technology to deterministic polishing.It uses the shear thickening characteristics unique to SRP fluids and special polishing head designs to deterministically remove material on the surface of workpieces to improve workpiece surface shape accuracy.The process of surface shape error correction mainly includes the construction of the experimental platform,the establishment of the removal function,the solution of the dwell time function,and the deterministic polishing experiment.This article will combine the characteristics of deterministic polishing with SRP to establish an experimental platform,analyze the rheological characteristics of the polishing fluid and the principles of DSRP,and establish a deterministic polishing removal function by combining hydrodynamic simulation and experiments.The fixed-point polishing experiment and BP neural network were used to establish a BP neural network model between the polishing process parameters and the peak removal rate of the polishing area.The BK7 flat glass was used as the polishing object to carry out the modification experiment.The specific research contents are as follows:An experimental platform was established based on the characteristics of DSRP,which mainly included force measuring devices,four-axis linkage systems,workpiece fixtures,and operation panels.Among them,the developed four-axis linkage system has a maximum spindle speed of 24000 rpm.XYZ axis accuracy can reach 10?m,which meet the experimental needs.The rheological properties of the SRP fluid were studied through a series of experiments to select the most suitable polishing fluid ratio for the DSTP process.According to the particularity of its polishing process,wedge-shaped polishing head was designed for determonistic polishing experiments.A DSRP removal function was established.First,the basic equation was established by combining the characteristics of DSRP with the classic Preston equation.Then the simulation was used to obtain the pressure and velocity field distributions and extract the data to fit a specific mathematical formula.Finally,according to the experimental results,the simulation correction coefficient and the polishing slurry concentration correction coefficient was determined,and the removal function was established.Furthermore,the correctness and stability of DSRP removal function were experimentally verified.Comparing the experimental results with the theoretical results under different polishing conditions,the two are basically the same in terms of the cross-sectional profile and the error is within 7%,which indicates that the established definitive polishing removal function has a higher value.Finally,the stability of the polishing process of the DSRP was investigated by polishing experiments with straight trajectories.Five cross-section profiles were uniformly selected on the surface of the polished workpiece for comparison.No large fluctuations were shown,indicating DSRP process has high stability.A BP neural network model for the peak removal rate of DSRP was established.First,orthogonal experiments of DSRP were performed.The experimental data was used for training BP neural network,and the accuracy of the model was tested using the test set data,the relative error is within 6.8%,which indicates that the output of the established neural network model has a high consistency with the experimental results,and provides a new idea for the establishment of the removal function of the entire polishing area.Comparing the output results of the BP neural network model with the calculation results of the removal function under the same experimental conditions in 6 groups,the relative error is within 8.7%,which further proves the accuracy of the established removal function.Finally,using BK7 flat glass as the experimental object,DSRP error correction experiment was carried out.First measure the initial shape of the workpiece to calculate the dwell time function,and then determine the meshing step size in the experiment by comparing the simulation results under different mesh step sizes.According to the determined grid step size,dwell time function and preset trajectory,the machine tool G code can be generated.Finally,the modification experiment was performed on the DSRP experimental platform.The surface error(PV value)of the BK7 flat glass after processing decreased from 6.87 ?m to 0.72 ?m.The surface error of the flat glass was successfully corrected using the DSRP method.