Research On Slow Tool Servo Turning And Form Accuracy Measuring For Complex Surface

Complex surface elements have wide application prospects because of the excellent characteristics.At present,they are mainly applied to military defense,space observation,optical system and civil life.Machining and measuring of complex surfaces are important factors limiting its wide application.Slow tool servo(STS)turning technology can achieve high precision turning of complex surfaces through three axis linkage.STS turning technology was developed in European and American countries and lots of available STS series machine tools were sold.Many universities and research institutes in our country have done some research on STS turning technology in recent years,but no industrial processing capability has been formed.In this paper,the construction of the STS experiment platform,the tool path generation(TPG)with simulation and the measurement of the workpiece surface error were studied.The major research works include the following points.1)TPG for STS turning of complex surface.The accuracy of TPG directly affects the final shape accuracy of complex surfaces.A local fitting method by Zernike polynomials was proposed.This method can realize the high precision generation of the cuting contact points(CCPs)without whole surface fitting.An equal height discretization method for CCPs was proposed.This method realized the control of discrete error and limited the height difference of adjacent CCPs.The tool shape compensation algorithms for different programming languages were proposed.The interpolation point velocity calculation method which can reduce the PVT interpolation error was proposed.This method transformed the segment cubic Hermite interpolation into segment cubic spline interpolation through matrix operation.Furthermore,the selection algorithm of interpolation points was optimized.2)The accuracy of TPG was analyzed by simulation.The sinusoidal array surface,toric surface and Zernike surface were chosen for simulation.The equal height,equal angle and equal arc length discretization method were used to generate the CCPs of these surfaces.Results showed that equal height discretization method can control discrete error distribution and reduce discrete error.In addition,the tool radius compensation algorithm based on MATLAB was more accurate.The accuracy of the three corner method for cutting location points(CLPs)velocity calculation was higher than three point method,but the velocity calculation was more complicated.The interpolation error was reduced by a certain range with interpolation point increase.A discrete form of progressive-addition lenses(PAL)was designed and evaluated by surface astigmatism and surface power distribution.By using discrete surface CCPs generation algorithm,the CCPs were generated successfully.Based on MATLAB software,the script file of NC machining program generation was written.3)STS turning experiments and surface error measurement for four kinds of complex surfaces were completed.A STS turning experimental platform with the core of IPC and motion control card was designed and developed.According to the IMAC400 controller,the servo system of each axis was debugged and PID parameters were optimized.The IPC control software of the experimental platform was developed The coordinate measuring machine(CMM)was used to automatically measure the surface data of complex surface workpieces with circumferential measuring path.As measuring head radius compensated for the workpiece meridian surface,the CFT tool in MATLAB was used to fit the compensated data.Better fitting method can be selected by the quantitative evaluation standards,thus the processing error can be calculated.The measurement results showed that the surface roughness can be controlled at around 90nm.The surface error of sinusoidal array surface and toric surface can be controlled at about ±0.01mm and±0.005mm,respectively.The surface error of Zernike surface and PAL surface can be controlled at about±0.02mm and±0.015mm,respectively.