Study On Micro Electrochemical Milling Of 304 Stainless Steel Micro Groove

Micro groove structure is a common structure in micro components and is widely used in MEMS.Due to the small size of micro groove structure and the machining of difficult-to-cut metal,its high precision machining is a challenge.Micro electrochemical milling technology has the advantages of good surface quality,no cutting force,no heat affected zone and no limitation of mechanical properties of machined materials.It is very suitable for machining the micro structure of metal materials that are difficult to machine.However,there are some problems in micro electrochemical milling,such as complexity of parameter control,being prone to stray corrosion,and difficulty in discharging electrolytic products in machining gap,which lead to poor machining accuracy.Therefore,this dissertation proposed a high precision machining method of micro electrochemical milling micro groove,which can reduce stray corrosion,improve machining stability and obtain a better combination of process parameters.The main work of this dissertation is as follows:（1）According to the electrochemical principle of electrochemical machining,the characteristics of electrochemical machining and micro electrochemical milling were analyzed.It was found that the pulse power supply with ultra short pulse width can reduce the stray corrosion and improve the localization of electrochemical machining.The influence of different factors on machining performance was analyzed,and an experimental equipment for micro electrochemical milling was developed based on the characteristics of micro groove machining.（2）The influence of electric field and flow field in machining gap on machining was studied by simulation.The electric field simulation results showed that the section shape is stable after a certain time and the milling speed should not be too small.The flow field simulation results showed that the overall flow velocity at the bottom of the micro groove section decreases with the increase of the milling depth,and the layered milling method should be adopted in the machining experiment.（3）When using H₂SO₄ solution as the electrolyte,the electrochemical dissolution characteristics of 304 stainless steel workpiece were studied by polarization curve experiment.The influence of different machining paths and sulfuric acid concentration on micro groove machining was compared and analyzed,then selected more number of layered depth,small feed milling way as machining path and 0.2 mol/L H₂SO₄ solution as electrolyte.（4）In order to reduce the stray current generated in electrochemical machining and improve the fluidity of electrolyte,C₂H₅OH solution was added into H₂SO₄ solution.The addition of C₂H₅OH significantly improved the machining stability and localization.The polarization curves of the workpiece were measured in the condition of H₂SO₄-C₂H₅OH compound electrolyte.It was found that the addition of C₂H₅OH did not change the electrochemical dissolution characteristics of the stainless steel workpiece.The effects of C₂H₅OH volume content in electrolyte,machining voltage,power frequency,power duty ratio and milling speed on micro groove machining were studied by single factor experiment.A set of better machining parameters were obtained by considering the machining accuracy and efficiency comprehensively.Under the better combination of parameters,the micro groove with length of 260μm,width of 93μm,depth of 42μm,cross section angle of 114°,surface roughness of Ra 0.39μm,and the material volume removal rate of 376.9μm³/s was machined,which had good surface quality and high shape accuracy.