Simulation Of Micro-milling Inconel718 Considering Size Effect And Optimization Of Cutting Parameter

Micro-milling is kind of new micro-fabrication technology,which can be used to efficiently and precisely form the three-dimensional complex structures on the parts with millimeter-level dimensions.So micro-milling can meet the technological requirements of micro parts.Compared with milling,the traditional cutting theory cannot explain the size effect in micro-milling process because of the scale reduction.Besides,the diameter of the micro milling cutter is small(usually between 50?m to 1mm)with low stiffness and the impact load and vibration is relatively large in micro-milling process,so the tool breakage is an important form of tool failure.It is important to select suitable cutting parameters for improving machining efficiency,quality and prolonging life of micro-milling cutters.To solve the above problems,this paper mainly studies the finite element simulation of micro milling process considering the size effect and the optimization of cutting parameters under the constraints of specific surface roughness and avoidance of cutter breakage.The size effect phenomena in micro-milling are studied by finite element simulation.First,based on the strain gradient plasticity theory,the modified Johnson-Cook(JC)constitutive equation is established to describe the material strengthening behavior.Then,considering the effects of the edge radius and the edge radius on rake angle,two-dimensional simulation model of micro-milling process considering the size effect is established.Finally,micro-milling Inconel718 experiments are organized to verify the simulation model considering the size effect proposed in this paper by comparing the measured unit cutting force and that of the simulation with unmodified JC constitutive equation and the modified JC constitutive equation respectively.Using the simulation model,the influence of different cutting thickness on cutting force and chip formation is discussed.The results show that the experimental cutting force is much fit the results based on modified JC constitutive equation,which explains the size effect in micromilling process.The simulation results of chip formation based on the modified JC constitutive equation explains the minimum cutting thickness.A series of research is studied on cutting parameters optimization in order to maximize the material removal rate when meeting the requirements of surface roughness and tool safety in the micro milling process.Based on the micro milling force model,the bending stress of the micro milling cutter is calculated,which is caused by distributed load along the spiral cutting edge.The ultimate stress of carbide micro milling cutter is obtained by experiment.Through comparing bending stress of the micro milling cutter calculated by cutting model to ultimate stress respectively,the prediction model of early breakage of micro milling cutter are obtained.Then,we establish a comprehensive floor surface model which may predict surface roughness of the grooves through the cutting parameters in micro milling.This model is based on movement trajectory of micro-end-mill considering vibration,workpiece surface forming considered elastic recovery and tool geometry.The final contour surface of the material is obtained combined the actual trajectory of the tool and the elastic recovery of the material,and the analytical model of the surface roughness of the micro milling is established.The actual movement trajectory during cutting process and the elastic recovery.Finally,the cutting parameters are optimized to pursue maximum MRR under the constraints of specific surface roughness and prevention of cutter breakage in the micro-milling process using genetic algorithm.The results can provide reference for increasing micro-milling efficiency and selection of cutting parameters.