Research On Key Processing Technology Of Vibration Assisted Micro Milling Of Thin Walled Microstructure

In this thesis,key technologies related to micro-machining are studied aiming at a new type of inertial sensor,of which part is a thin-wall micro-structure,and its characteristic size is only 10?m.The advantage of mechanical sensing part is its inherent immunity to electrical interferences.Micro milling technique is often used to manufacture these kinds of parts,but due to the small size of the milling tools,tool life is much shorter than conventional milling process.The worn cutting tool often leads to poor surface finish and significant deformation of the thin wall structure.In this paper,a vibration assisted micro milling process is introduced to solve such problems.A precision vibration assisted milling based on new vibration form device is designed.Due to the large mass of the milling spindle,the auxiliary vibration is selected to be applied onthe workpiece.The vibration device uses piezoelectric ceramics to drive a flexible hinge mechanism to achieve the vibration output.Different with traditional resonant mode vibration devices,this design adopts a pair of piezoceramics driven with 180-degree phase difference on oppsite side of the moving part.The pull-push working mode increased the input power of the vibration device and thus helps to achieve non-resonant mode vibration.Beacause of the non-resonant property,the vibration frequency and amplitude can be adjusted to suit different cutting conditions.At the same time,the vibration device developed in this paper can also be used to monitor the cutting force of the micro milling process.The monitoring function is achieved by using a pair of piezoceramics as sensing elements.By analyzing the spectrum of the detected signal,the wear status of the tool can be estimated to the intensity percentage of the fundemantal frequency signal.The development of the vibration assisted system has laid a foundation for the subsequent experimental research.The analysis of cutting force is an important approach to study the mechanism of vibration assisted micro-cutting.As the size of the micro milling cutter is comparable to the error motions of the milling spindle.Also with the introduction of assisted vibration,the variation of themicro milling force is quite different from the macro scale milling.Therefore a mathematical force model of vibration assisted milling is established by considering the influence of the tool eccentricity error,tool equivalent rake angle,vibration frequency and amplitude of the milling cutter.The accuracy of the model is verified by experimental milling process.Based on this model,the influence of assisted vibration on the material removal process is studied via cutting force analysis,and finally the theoretical basis for improving the micro milling condition by introduction of assisted vibration can be obtained.Effects of vibration assistance on surface roughness,profile accuracy and tool wear of thin-wall micro-structure are studied.Based on the orthogonal cutting experiment method,the influence of machining prameters such as the feed per tooth,depth of cut,frequency and amplitude of the vibration,on the resulted surface roughness Ra is studied.Also,the cutting burr size is found to be reduced through vibration assisted milling.Optimum process parameters are selected.The wear process of the micro milling tool is studied by applying vibration and the influence of added vibration on the wear process and wear pattern of the milling cutter is obtained.In order to directly verify the machenical performance of the flexible structured part,a thorough micro-tensile test is conducted.In this paper,the influence of assisted vibration on the elastic modulus,tensile strength,yield strength,elongation and fault area of the thin-walled micro part is studied by using an existing micro component mechanical property test device.Based on this,the regression model between surface quality and mechanical performance is established.Using this regression model,the mechanical properties of the thin-walled micro part can be predicted by the surface topography information only.This lays concrete foundation of the successful application of this type of thin-walled micro-component in aviation systems.