Plasma-enabled electrochemical jet micromachining of chemically inert and passivating material

Electrochemical jet machining(EJM)encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface,preventing the progress of electrochemical dissolution.This research demonstrates for the first time a jet-electrolytic plasma micromachining(Jet-EPM)method to overcome this problem.Specifically,an electrolytic plasma is intentionally induced at the jet-material contact area by applying a potential high enough to surmount the surface boundary layer(such as a passive film or gas bubble)and enable material removal.Compared to traditional EJM,introducing plasma in the electrochemical jet system leads to considerable differences in machining performance due to the inclusion of plasma reactions.In this work,the implementation of Jet-EPM for fabricating microstructures in the semiconductor material 4H-SiC is demonstrated,and the machining principle and characteristics of Jet-EPM,including critical parameters and process windows,are comprehensively investigated.Theoretical modeling and experiments have elucidated the mechanisms of plasma ignition/evolution and the corresponding material removal,showing the strong potential of Jet-EPM for micromachining chemically resistant materials.The present study considerably augments the range of materials available for processing by the electrochemical jet technique.

Improving performance of macro electrolyte jet machining of TC4 titanium alloy:Experimental and numerical studies

Electrolyte jet machining(EJM)is a promising method for shaping titanium alloys due to its lack of tool wear,thermal and residual stress,and cracks and burrs.Recently,macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or planes.However,macro-EJM generates large amounts of electrolytic products,thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface quality.Therefore,for enhanced product transport,a novel tool with a back inclined end face was proposed for macroEJM of TC4 titanium alloy.For comparison,also proposed were ones with a standard flat end face,a front inclined end face,and both front and back inclined end faces.The flow field distributions of all proposed tools were simulated numerically,and experiments were also conducted to validate the simulation results.The results show that one with a 5°back inclined end face can decrease the lowvelocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool,thereby promoting rapid product removal.A relatively smooth bright-white groove surface was obtained.The same tool also resulted in the highest machining depth and material removal rate among the tested ones.In addition,rapid product removal was beneficial to the subsequent processing.Because of its rapid product removal,the machining depth and material removal rate during deep groove machining using the tool with a 5°back inclined end face were respectively 7%and14%higher than those produced using a standard one.Moreover,the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm,and a plane with a depth of0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5°back inclined end face.

Theoretical and Experimental Investigation of Laser Milling Assisted with Jet Electrochemical Machining

In laser milling assisted with jet electrochemical machining(LMAJECM),the source of energy is a pulsed laser beam aligned coaxially with a jet of electrolyte,which focuses optical energy on the surface of workpiece.The impact of jet of electrolyte develops a state-of-art work to perform operations such as electrolytic etching,effective cooling,and transportation of debris.Therefore,a special jet cell is designed to obtain stable jet as to be a kind of noncontact tool,i.e.,electrode.According to the theoretical model of on-off pulse time process,laser machining and electrolytic anodization are simulated by finite element analysis(FEA)method.Grooves on a 0.5mm thick 321 stainless steel sheet produced by LMAJECM is performed with pulsed Nd:YAG laser at the second harmonic wavelength.Compared with laser milling under ambient atmosphere conditions,the recast layer and burrs are effectively diminished.And the accuracy of depth is dedicated to laser milling,whilst that of width is dominated by jet electrochemical machining.It is demonstrated that LMAJECM can be a highly potential approach for fabricating 3-D micro components.