Research On Non-resonant 2-DOF Vibration Assisted Micro-milling

Vibration assisted micro-machining has become a major machining method when machining micro parts with complex structure and special functions.It has the advantages of reducing cutting force,reducing tool wear,reducing burr formation and improving surface finish.At the same time,the machining parameters of micro-milling are usually micron level,so the size effect and tool run-out are very important for the calculation of cutting force.In order to achieve the purpose of vibration assisted precision machining,the non-resonant 2-Degree of Freedom(2-DOF)vibration assisted micro-milling is studied by using the method of theoretical modeling and simulation analysis.The thesis is mainly carried out in the following aspects:1.Based on the compliant mechanism,a new non-resonant 2-DOF compliant vibration stage is designed.The symmetrical arrangement of the dual leaf parallelogram hing(DLPH)and the leaf-spring flexible hinge(LSFH)are adopted to reduce coupling errors and parasitic motion of the stage.On the basis of theoretical modeling,the equivalent dynamic model of the 2-DOF compliant vibration assisted stage is established.The dynamic and static characteristics of the stage are studied by theoretical calculation and finite element analysis.Its first-order natural frequency and limit working stroke are 4144.9 Hz and 22.59μm,respectively.2.The first-order natural frequency and limit working stroke of the non-resonant2-DOF compliant vibration stage are optimized.The finite element analysis method is used to establish the orthogonal test,and the response relationship between the prediction model and the structural parameters of the flexure hinge is established by the response surface method.Based on the response surface,the multi-objective optimization genetic algorithm is introduced to obtain the optimal balance solution of the vibration stage in the design space.Through the comparison of theoretical modeling and finite element simulation,the optimized first-order natural frequency and limit working stroke are 4267.6 Hz and 23.30μm,which are increased by 2.96% and 3.14%,respectively.3.Based on the mechanical analysis method and the force model of oblique cutting element,the 2-DOF vibration assisted micro-milling cutting force model of aluminum alloy6061 is established according to the shear area and plough area.Considering the tool run-out,the effect of the size effect and cumulative effect on the instantaneous uncut cutting thickness(IUCT)in the actual cutting process,and combining the kinematic characteristics of 2-DOF vibration assisted micro-milling,the instantaneous uncut cutting thickness model of 2-DOF vibration assisted micro-milling is established.The cutting force of aluminum alloy 6061 is simulated by Matlab software,and the cutting force curves in x and y directions under the effects of amplitude and vibration frequency are obtained,respectively.4.Based on the existing micro-milling system,the non-resonant 2-DOF vibration assisted micro-milling system is constructed.Taking aluminum alloy 6061 as the test object,the optimized non-resonant 2-DOF compliant vibration stage is used to provide excitation for the workpiece.And the non-resonant 2-DOF vibration assisted milling test is carried out with 2-flute flat-end milling cutter to analyze the influence rules of amplitude and frequency on cutting force,respectively.By comparing the cutting force curves of simulation and experiment,the correctness and feasibility of the proposed 2-DOF cutting force model for vibration assisted micro-milling are verified.