Analysis And Compensation Of Slender Cutter Deflection On Machining Error Of Mould Surface

Mould is an important technological equipment in manufacturing industry,which not only occupies an important position in the development of national economy,but also reflects the level of a country’s science technology and product manufacturing.The finishing process of mould cavity surface was taken as the research object,and the effect of slender cutter deflection on cutting force,machined surface topography and machining error were investigated by the developed models of cutting force and slender cutter delflection.The main research works are summarized as follows:(1)The cutting force prediction model of the ball end milling cutter was developed by considering the real cutting edge trajectory,in which the cutter-workpiece engagement and uncut chip thickness were determined based on the proposed triangle mesh and numerical iterative method.The correlation among the cutting parameters,cutter-workpiece engagement,uncut chip thickness and cutting force were investigated.The simulation and experimental results of cutting force show that the prediction model of cutting force has high accuracy.The cutter runout,feed per tooth,radial depth of cut and the axial depth of cut all have significant effect on peak cutting force.The tilt angle,feed per tooth,radial depth of cut and the axial depth of cut all have significant effects on average cutting force,while the effect of cutter runout on the average effect is not significant.The cutter-workpiece engagement,undeformed chip thickness,peak cutting force and average cutting force show a consistent trend with the change of cutting parameters.The calculated results of Pearson’s correlation coefficients show that the peak cutting force along the directions of radial depth of cut and cutter feed are with the strongly correlated with the maximum thickness,the average cutting force along the directions of radial depth of cut,cutter feed and cutter axis are strongly correlated with and the area of cutterworkpiece engagement.(2)An iterative calculation model of the slender cutter deflection was developed based on the four-section cantilever beam and the balance of cutting force and the elastic force,which considers the force and cross section characteristics of the cutter and the feedback effect of the deflection on the cutting force.The slender cutter deflection and its influence on the cutting force were analyzed.The maximum deflection at the cutter location point increases with the increase of cutter overhang length,cutter runout,feed per tooth,radial depth of cut and axial depth of cut.The maximum deflection at the cutter location point in the direction of radial depth of cut decreases first and then increases gradually with the increase of the tilt angle,while the maximum deflection at the cutter location point in the feed direction decreases gradually with the increase of the tilt angle.The average deflection at the cutter location point increases gradually with the increase of cutter overhang length,feed per tooth,radial depth of cut and axial depth of cut,while the average deflection at the cutter location point decreases gradually with the increase of tilt angle and cutter runout.The simulation results of cutting force considering the slender cutter deflection are smaller than those without considering the deflection,and the variation of cutting force and the deflection at cutter location point show a consistent trend with the change of cutting parameters.The variation of the peak cutting force is highly correlated with the variation of the maximum deflection at the cutter location point,the variation of the average cutting force in the feed and cutter axial direction are highly correlated with the variation of the average deflection at the cutter location point,which indicates that the slender cutter deflection has a significant influence on the cutting force.(3)The 3D machined surface topography simulation model based on triangular mesh of modified cutting edge trajectory was developed,and the influence of cutting parameters and slender cutter deflection on 3D machined surface topography was revealed.The comparative analysis of the experimental results and the simulation results of the machined surface topography and its arithmetic mean deviation show that the simulation model has high accuracy,which verifies the validity of the simulation model.The arithmetic mean deviation of 3D machined surface topography increases gradually with the increase of feed rate per tooth and radial depth of cut,and the increasing rate increases with the increase of feed rate per tooth and radial depth of cut.The feed per tooth and the radial depth of cut have a very significant effect on arithmetic mean deviation,and the cutter runout and tilt angle have a significant effect on arithmetic mean deviation,while the cutter overhang length and the axial depth of cut have no obvious effect on arithmetic mean deviation.The simulation results of the arithmetic mean deviation when considering the slender cutter deflection are smaller than those without considering the deflection,indicating that the slender cutter deflection has the effect of reducing the arithmetic mean deviation.The optimization of feed per tooth and radial depth of cut can effectively reduce the arithmetic mean deviation and machining time.(4)The relationship between the deflection at the cutter location point and the machining error was analyzed.The influence of the slender cutter deflection on the machining error of mould surface was revealed.An iterative compensation model for the machining error based on the nominal cutter path was proposed,and the effectiveness of the compensation model was evaluated.The simulation results and experimental results of the maximum error of cylindrical contour machining increase with the increase of the axial cutting depth,and the amplitude of the increase is consistent.The slender cutter deflection has a significant effect on the machining error of the mould surface,and the influence increases with the increase of axial depth of cut.The experimental results of the maximum error of cylindrical contour machining after compensation for the slender cutter deflection are obviously smaller than those without compensation.Compared with the experimental results of cylindrical surface contour machining error fluctuation range without compensation for the slender cutter deflection,the experimental results of cylindrical surface contour machining error fluctuation range with compensation for the slender cutter deflection are greatly reduced.The fluctuation range of experimental results of the cylindrical surface contour machining error are controlled within 1μm after compensating the slender cutter deflection.The above results show that the error compensation of slender cutter deflection can effectively reduce the maximum machining error and the fluctuation range of the machining error of the molud surface,and then improve the machining accuracy of the mould surface.In this paper,aiming at the problem of slender cutter deflection and machining error in ball-end milling of mould surface.The influence of slender cutter deflection on the cutting force,3D machined surface topography and the machining error were analyzed.An iterative compensation model for slender cutter deflection based on nominal cutter path was established.It provides the corresponding theoretical support and technical support for improving the machining accuracy of mould surface.