The Spindle Error Compensation And Thin-walled Part Vibration Analysis For Twin Facing Lathe

The compressor disk is regarded as one key part of the aero-engine and its machining is an enormous challenge.Compressor disk is a kind of thin plate with variable thickness and large diameter,which is prone to vibrate and deform during machining due to its weak stiffness.In this study,the compressor disk was machined by a self-built intelligent CNC twin facing lathe.The lathe spindle was supported by two bearings with large diameter and short wheelbase.The rotational run-out error of the spindle end face caused by manufacturing accuracy and assembly accuracy of the bearings cannot be ignored.This kind of error will eventually be reflected in the machined parts.The above-mentioned two factors can affect the machining accuracy of the parts,and therefore,they were investigated in this dissertation.First of all,dynamics analysis of the thin annular plate was done based on thin plate hypothesis and Kirchhoff plate hypothesis.The transverse shear force,bending moment and torsion moment of the plate were derived under Polar Coordinates.Linear springs and torsion springs were used to simulate various boundary conditions through stiffness coefficients by setting different stiffness coefficient in this dissertation.A particle system was composed of a disc and two kinds of springs.Its kinetic energy and potential energy were computed,then the Lagrange equation of the particle system was presented by using the Hamilton principle.It was of most importance to construct basic functions by cosine functions and polynomial functions.And then a linear combination of basic functions was used to approximate the radial shape function of the annular plate.In this way,the problem of minimizing the Lagrange’s function on the amplitude of the vibration was transformed into the minimum value of the general multivariate function,which can solve the undetermined coefficient introduced by the linear combination.With this approach,the natural frequencies and modal shapes of the plate were obtained.The calculation results were compared with finite element simulation results by ABAQUS,validating the accuracy and effectiveness of the method in this dissertation.In addition,this method has wide applicability,because it is useful to use the same model to solve different boundary constraint problem of the plate.The spindle end face run-out rotation error of twin facing lathe was studied.Firstly,it was proved that the spindle rotation error was good in reproducibility and had nothing to do with the working condition,which was the static error of the lathe.The spindle rotation error can be divided into the shifting error and the deflection error.Surface topography of multiple torus was measured with Coordinate Measuring Machine(CMM)after turning.Then the shifting error,the deflection error,parallelism of X axis and positioning error of Z axis can be separated through data processing.Spindle rotation error compensation(SREC)was done relying on error curve and by using fast tool servo,which obviously reduced end face run-out error.The effectiveness of error compensation was confirmed.