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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]

Abstract: A new micromachining method for the fabrication of micro-metal structures by using micro-reversible electrical discharge machining (EDM) was investigated. The reversible machining combines the micro-EDM deposition process with the selective removal process, which provides the ability of depositing or removing metal material using the same micro-EDM machining system. From the discharge mechanism of micro-EDM, the process conditions of micro-EDM deposition were analyzed firstly. Using the brass and steel materials as a tool electrode, the micro-cylinders with 200μm in diameter and height-to-diameter ratio of more than 5 were deposited on a high-speed steel surface. Then the machining procedure was transformed easily from deposition to selective removal process by switching the process conditions. Different removal strategies including micro-EDM drilling and micro-EDM milling were used in the machining. Micro-holes with 80μm in diameter are drilled successfully in the radial direction of the deposited micro-steel cylinder. Also, a brass square column with 70μm in side length and 750μm in height, and a micro-cylinder with 135μm in diameter and 1445μm in height are obtained by using micro-EDM milling. Finally, the characteristics of the deposited material were analyzed. The results show that the material components of a deposited micro-cylinder are almost the same as those of the tool electrode, and the metallurgical bonding has been formed on the interface. In addition, the Vickers-hardness of 454Hv of the steel deposited material is higher when compared to the hardness of 200Hv of the raw steel electrode. [Copyright &y& Elsevier]

C f -ZrB 2 -SiC is a new composite material with excellent properties for making the next-generation aerospace component. This material is extremely difficult to removal by mechanical machining, and there is a lack of research on feasible secondary processing methods of this composite at present. Micro-EDM is not limited by material hardness, so it is very suitable for machining this material. In this paper, the Material removal mechanisms and processing characteristics of C f -ZrB 2 -SiC by micro-EDM is analyzed. The removal mechanism of composite materials is explored though the discharge crater morphology, and the single-discharge experiments of each phase materials with different medium and different energies are also carried out as a reference. Electrical discharge milling experiments of C f -ZrB 2 -SiC are performed to explore the medium on processing index, and found that the best surface quality and maximum processing efficiency can be realized in kerosene. An experiment with four factors (pulse width, voltage, peak current, capacitance) and three indexes (surface roughness, MRR, TWR) is designed to analyze the C f -ZrB 2 -SiC process characteristics of micro-EDM and the response surface diagram and second-order regression equation are obtained. Milling the C f -ZrB 2 -SiC by electrical discharge according to the optimal combination of surface roughness parameters deduced above, the as-machined surface is analyzed including the surface morphology by SEM, element content by EDS and the surface phase by XRD. The feasibility and advantages of micro-EDM on machining C f -ZrB 2 -SiC are prove. [ABSTRACT FROM AUTHOR]

Abstract: In micro-wire electrical discharge machining (micro-WEDM), the machined kerf width varies with different machining parameters, which greatly influences the machining precision. In order to study the kerf variations in micro-WEDM, the mathematical model of wire lateral vibration in machining process is established and its analytical solution is obtained in this paper. The model is practically verified on a self-developed micro-WEDM machine. Under this model, a 30.8μm width slot is achieved on a stainless steel workpiece with ∅30μm wire-tool. [Copyright &y& Elsevier]