Dynamic Responses And Surface Topography Prediction In Micro Milling Process

With the development of miniaturization and integration of equipment,micro-parts are increasingly used in aerospace,defense industry,biomedical,electronic information and other fields.Micro milling is the main method to machine micro parts with its unique advantages.Due to the small size and poor rigidity of the micro-end mill and workpiece,severe size-dependent vibration occurs during the micro milling process,which affects the life of the micro-end mill,limits the machining efficiency,reduces machining accuracy and surface quality.Based on the strain gradient elastic theory,this paper discusses the influence of size effect on the vibration response of micro-end mill and workpiece,studies the formation mechanism of surface morphology in micro milling process,achieves efficient and precision machining,and provides theoretical basis for vibration suppression and machining parameter optimization.Firstly,a dynamic model and solving method of micro-end mill considering size effect is proposed,and the influence mechanism of size effect on micro-end mill vibration response is revealed.The micro-end mill is simplified to the Timoshenko beam model.Based on the strain gradient elastic theory and the Hamilton's principle,the dynamic model of the micro-end mill considering the size effect is established,and the dynamic model is solved by the finite element numerical solution.The dynamic model contains three material length scale parameters that reflects the size effect of the micro-end mill.The study found that the stiffness and the natural frequency increase,and the static deformation and dynamic response decrease after considering the size effect.Then,a dynamic model of micro thin-walled plate is established to predict the vibration response and stability in micro milling process.The micro-thickness plate is simplified into the Kirchhoff plate model.Based on the strain gradient elasticity theory and the Hamilton's principle,the dynamic model of micro-thickness plate considering size effect is established.The micro milling force moving along the cutting path is taken as a moving load,and the size-dependent vibration response of micro-thin plate under the moving load is researched.The stability lobe of micro thin-walled plate considering the size effect is obtained by the differential quadrature method.The results show that the stiffness of the micro-thickness plate increases,and the response of the micro-thickness plate decreases under the moving load and the system stability increases after considering the size effect.Finally,a flexible micro milling force model considering the size-dependent vibration of micro-end mill is established.The surface topography prediction method in micro milling process is proposed,and the factors that affect the surface topography in micro milling process are studied.Considering the feedback of size-dependent vibration of micro-end mill on the micro-milling force,a flexible micro-milling force model is established.Considering the size-dependent vibration of micro-end mill under the flexible micro milling force,the micro-end mill runout and the elastic recovery in the plough region caused by the cutting edge radius,the surface topography is simulated based on the cutting edge trajectory.The results show that the surface roughness increases considering the micro-end mill vibration.At the same time,the surface roughness considering the size effect is reduced compared with the surface roughness without considering the size effect.