Modeling Method And Experimental Study On Ball-End-Milling Surface Topography

Surface topography of the parts has great influence on the contact state,surface wear,lubrication state,friction,vibration and so on of the joint.The rapid obtaining of the surface topography of the machined surface is very important for the realization of precision manufacturing and intelligent manufacturing.Ball-end-milling cutter has been widely used in the parts processing of aerospace,die and automobile industries due to its strong adaptability.However,for the high precision surface,the process that polishing after ball-end-milling is adopted to machining most of them.It not only consumes time and energy,but also results in poor surface quality consistency.With the continuous improvement and perfection of high speed machining technology,multi-axis control technology and precision manufacturing technology,it has become possible to achieve or approach the final surface quality requirements of parts through precision milling with ball-end-milling cutter.However,the shape of the cutter tooth of the cutter is complex,the contact point between the cutter tooth and the workpiece is constantly changing during cutting,and the influence mechanism of geometric and physical factors on the formation of the surface topography in the milling process is complex.Therefore,it is of great significance to study the forming mechanism of the surface topography in the ball-end-milling process and to generate the surface topography rapidly under different cutting conditions for the prediction of the combined performance of parts and intelligent manufacturing.From the perspective of kinematics,statics and dynamics of the milling process,modeling and simulation of ball-end-milling surface topography is taken as the main research line in this paper,and it is realized on the bases that establishing the ball milling cutter head milling cutter tooth in the process of kinematics model,calculating milling force,analyzing milling stability,and solving the vibration induced dynamic displacement of the cutter and workpiece.Related researches about the forming of ball-end-milling surface are completed,and a basis for the selection of milling parameters is provided so as to improve the surface quality,specific as follows:Based on the principle of homogeneous coordinate transformation,the kinematics model of ball-end-milling process is established,which takes into account not only the driving effect of cutting parameters on motion,but also the influence of cutter posture adjustment and radial runout,which lays a foundation for the geometric and physical simulation of surface topography.On this basis,the improved Z-MAP method,a geometric simulation method for ball-end-milling surface topography,is proposed.The results of simulation and experiment are compared,and the influence law of various parameters on the surface topography of rigid cutter-rigid workpiece system is analyzedTwo kinds of methods about modeling and simulation of rigid force of the ball-end-milling,based on the improved Z-MAP modeling method and the semi-analytical modeling method,are puts forward.Recognition methods of cutter workpiece engagement region of corresponding to these two methods are proposed respectively,the calculation method of undeformed chip thickness is presented based on the Newton method,and the cutting force coefficient related to axial position angle of the cutter tooth is identified,and the instantaneous forces acting on the cutter in the X,Y and Z directions are solved by using the homogeneous coordinate transformation and the numerical integration principle.On these bases,the differences between the two modeling methods of cutting forces are compared in the endThe cutting state equation of ball-end-milling process is established,and the solution method of dynamic stability of the process under the effect of regeneration with variable time delay is proposed.The flexible ball-end-milling system is divided into three systems:flexible cutter-rigid workpiece system,rigid cutter-flexible workpiece system and flexible cutter-flexible workpiece system.Dynamic equations of these three milling systems are established under the effect of regenerated vibration and characteristic of variable time delay.Based on these dynamic equations,a full discretization method,in which variable delay is taken into account,is presented to analyse stability of the flexible milling system,and to solve dynamic displacements of cutter and workpieceA kinematics equation updating method about ball-end-milling process is put forward according to the cutter and workpiece dynamic displacement time history,and the physical simulation method of ball-end-milling surface topography about flexible milling systems is established based on Z-MAP method and Taylor formula.Based on this,the influences of machining parameters on the dynamic displacement of cutter and workpiece and the surface topography in different milling systems are analyzed,which can provide a basis for the selection of cutting parameters and the improvement of surface quality in actual machining.