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This paper develops a new combined technology to fabricate complex 3D microstructure based on micro milling and micro sinking electro-discharge machining (micro-SEDM). Graphite microform electrode is in-situ prepared by micro milling and subsequently used for micro-SEDM, integrating the advantages of two processes. Material removal rate (MRR) and electrode wear ratio (EWR) are experimentally investigated to determine proper parameters for different micro-SEDM performances. Three different machining strategies including single, double and treble micro-SEDM are adopted to fabricate 3D microstructure. The surface roughness, size accuracy, machining duration and cost of micro-cavities, and electrode wear under different strategies have been compared. The results show that treble micro-SEDM produces superior surface quality with 0.83 μm Ra and size accuracy with ≤ 28.05 μm tolerance. The proposed method broadens the machining flexibility and capability of micro-fabrication techniques. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid process combine micro reciprocated wire-EDM which uses reciprocated travelling wire with 50 μm diameter as tool electrode, with the precision forging, achieving the economical and high-efficiency sustainable production of micro gears. A micro gear mold with 0.1 mm module and 10 tooth number is devised, and the 14.5 μm mold fit clearance is determined by analyzing the established mold matching model and conducting the numerical simulation of precision forging. During the micro reciprocated wire-EDM of micro gear mold from SKD11, the basic experiments are performed to study the effect of the main parameters on machining accuracy and productivity, and whilst the proper machining parameters are obtained. The micro gear punch and die are successfully fabricated by micro reciprocated wire-EDM, showing good surface quality with 0.90 μm and 0.83 μm Ra respectively, and low dimensional deviations of ≤1.3 μm and 2.1 μm respectively. Finally, the precision forging of the micro gears are conducted on ultrafine grained (UFG) high purity copper by the machined micro gear mold. The forged micro gears have high forming precision with ≤4.1 μm deviation from the micro gear mold and smooth surface with 0.86 μm copied from the micro gear die cavity, verifying the feasibility of the proposed method for the sustainable production of micro gears. [ABSTRACT FROM AUTHOR]

Tool electrode wear varying with different materials in electrical discharge machining (EDM) is unavoidable, thus inevitably reducing the machining quality and accuracy of microstructures. To convert this disadvantageous phenomenon into a beneficial process, the paper proposed a wear-variation EDM (WV-EDM) approach to fabricate a laminated disc electrode (LDE) with stable-shape micro channels on the outer edge surface; this electrode was subsequently used to machine micro grooves on workpieces by EDM. The WV-EDM formation of the LDE, the relationship between relative volume wear rate of the disc foils and the machining depth, and flow field distribution in the machining gap of the LDE during processing were investigated. The results show that the method proposed herein could reliably produce LDEs with stable micro channels on the outer edge surfaces that could subsequently be employed to continuously machine micro groove arrays with the same machining depth on the same material workpiece by EDM, and especially LDE reshaping was unnecessary. Additionally, the "pump effect" of the vortex, located in the flow field between micro channels on the LDE and workpiece, was beneficial for debris removal. Using the proposed method, micro groove arrays and columnar microstructures were successfully fabricated on Ti–6Al–4V alloy workpieces. [ABSTRACT FROM AUTHOR]

With three-dimensional (3D) microelectrodes used to machine microcavities in microelectrical discharge machining (micro-EDM), the processing efficiency can be greatly improved. However, the surfaces of a laminated 3D microelectrode always have stair steps, which will be further copied to the machined surfaces of the microcavities, reducing the processed surface quality. To solve the problems, the paper proposed using layer-by-layer scanning microelectrochemical machining (micro-ECM) to eliminate the stair-stepping effect of the laminated 3D microelectrodes. First, wire electrical discharge machining (WEDM) was chosen to cut Cu foils for obtaining multilayer two-dimensional (2D) microstructures. Second, the multilayer 2D microstructures were applied to thermal diffusion bonding to form 3D microelectrode blanks. Then, the 3D microelectrode blanks were processed via layer-by-layer scanning micro-ECM to eliminate the stair steps on the surfaces. The influences of applied voltage, offset distance, and layer thickness on the elimination of the stair-stepping effect were investigated in details. Experimental results show that the stair steps on the laminated 3D microelectrode surfaces were eliminated obviously under 4.0 V applied voltage, 200 μm offset distance, and 20 μm layer thickness. Finally, the laminated 3D microelectrodes without stair steps on the surfaces were applied to micro-EDM to process microcavities. Two typical microcavities without the stair steps were obtained. [ABSTRACT FROM AUTHOR]