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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 the manufacture of micro-rotating structure combining micro reciprocated wire electrical discharge machining (wire-EDM) and multi-cutting strategy. A novel rotating spindle is developed to achieve the rotation of cylindrical workpiece and the multi-cutting strategy including rough, semi-finish, and finish machining is attempted to improve the machining removal rate (MRR) and reduce the surface roughness (SR) of micro-rotating structure. To determine proper parameters for multi-cutting process, the effects of machining parameters such as open voltage, discharge capacitance, and rotation rate on MRR and SR are studied by systematically performing experiments planed by single factor design and central composite design (CCD) of response surface methodology (RSM). Analysis of variance (ANOVA) is conducted to identify the significant factor and confirm the adequacy of the established models of MRR and SR. The mathematical models are used to predict MRR and SR within 8.18 and 8.74% prediction error compared with the additivity tests, respectively. Desirability method in RSM technique is used to determine three sets of parametric combinations for multi-cutting process, which are verified by confirmation experiments with 1.75~7.76% prediction error for MRR and 2.77~8.59% prediction error for SR. Finally, a typical microballoon probe is successfully machined with 0.435 Ra and 98.7-μm diameter by the proposed method, which provides a feasible approach for the fabrication of micro-rotating structure with high efficiency and smooth surface. [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]

Wire electric discharge machining (WEDM) and electrical discharge machining (EDM) promise to be effective and economical methods for the machining of metal matrix composites and conducting ceramic blanks. However, the machining process of Ni-AlO functionally graded materials (FGMs) is extremely difficult because the insulating ceramic layer cannot be machined directly by EDM. In this paper, the pure AlO layer has been machined by self-induced EDM, using the conductive layers of Ni-AlO FGMs to trigger the discharges in the insulating ceramic layer. Machining experiments have been performed to investigate the effects of discharge capacitance, pulse off-time, and charging resistance on the process performance of the pure AlO layer using RC-type pulse generator. From the experimental results, the discharge waveform of pure AlO layer includes long pulse discharge waveform, in addition to conventional normal discharge of conductive layers. The shape of long pulse discharge waveform can be changed by pulse off-time. The appropriate pulse off-time not only improves the stability of EDM but also increases the material removal rate (MRR). Moreover, it was observed that the MRR increases with increasing discharge capacitance and decreasing charging resistance. The surface roughness increases with increasing discharge capacitance. Finally, a small hole with a depth-diameter ratio of 5, little tapper is machined based on the experimental analysis. [ABSTRACT FROM AUTHOR]

Ni-AlO functionally graded materials (FGMs) have become important for high-temperature applications due to a continuous change in composition. However, the manufacturing of Ni-AlO FGMs with conventional machining methods is a long and costly process because of the insulating ceramic composition. This paper presents a new method of machining Ni-AlO FGMs by self-induced electrical discharge machining (EDM). Self-induced EDM uses the conductive compositions of Ni-AlO FGMs to trigger the discharges in the insulating composition. Machining characteristics of a four-layered Ni-AlO FGMs drilled by self-induced EDM have been investigated, which include the material removal mechanisms, discharge properties, surface characteristics, material removal rate, and electrode wear ratio. It has been found that graded layers, 70 % Ni-graded layer and 30 % Ni-graded layer, are removed by dislodgement of AlO particles, in addition to conventional melting and evaporation. Pure AlO layer is melted and evaporated by utilizing conductive layer-induced discharges. The discharge properties, surface characteristics, material removal rate, and electrode wear ratio are significantly influenced by the material removal mechanisms of graded compositions. These findings demonstrate that self-induced EDM is able to effectively machine Ni-AlO FGMs. [ABSTRACT FROM AUTHOR]

Although helical electrodes have been proven to improve the EDM (electrical discharge machining) speed of small holes, there are few studies on the morphological characteristics of the machined small holes and the influence of electrode structures. In this paper, the influence of the helical electrode structure on the machining effect is studied by the method of orthogonal experiment, and the internal mechanism of the influence of the helical electrode on the machining is explained by the method of CFD (computational fluid dynamics) simulation. The results show that the larger depth and width of the helical groove and the helix angle of 60° are beneficial to increase the machining speed and reduce the relative loss rate, and at the same time, avoid serious defects in the small hole morphology. These conclusions provide a valuable reference for future researchers to choose the reasonable structure of the helical electrode, which is of great significance. [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]

Network microstructure titanium matrix composites (NMTMCs), featuring Ti6Al4V as the matrix and network-distributed TiB whiskers (TiBw) as reinforcement, exhibit remarkable potential for diverse applications due to their superior physical properties. Due to the difficulty in machining titanium matrix composites, electrical discharge machining (EDM) stands as one of the preferred machining techniques for NMTMCs. Nevertheless, the compromised surface quality and the recast layer significantly impact the performance of the workpiece machined by EDM. Therefore, for the purpose of enhancing the surface quality and restraining the defects of NMTMCs, this study conducted comparative EDM milling experiments between NMTMCs and Ti6Al4V to analyze the effects of discharge capacitance, charging current, and pulse interval on the surface roughness, recast layer thickness, recast layer uniformity, and surface microcrack density of both materials. The results indicated that machining energy significantly influences workpiece surface quality. Furthermore, comparative experiments exploring the influence of network reinforcement on EDM milling revealed that NMTMCs have a higher melting point, leading to an accumulation phenomenon in low-energy machining where the reinforcement could not be completely removed. The residual reinforcement in the recasting layer had an adsorption effect on molten metal affecting the thermal conductivity and uniformity within the recasting layer. Finally, specific guidelines are put forward for optimizing the material's surface roughness, recast layer thickness, and uniformity, along with minimizing microcrack density, which attain a processing effect that features a roughness of Ra 0.9 μm, an average recast layer thickness of 6 μm with a range of 8 μm, and a surface microcrack density of 0.08 μm−1. [ABSTRACT FROM AUTHOR]

Micro-liquid floated gyroscopes are widely used in nuclear submarines, intercontinental missiles, and strategic bombers. The machining accuracy of micro-ball sockets determined the motion accuracy of the rotor. However, it was not easily fabricated by micro-cutting because of the excellent physical and chemical properties of beryllium copper alloy. Here, we presented a linear compensation of tool electrode and a proportional variable thickness method for milling micro-ball sockets in C17200 beryllium copper alloy by micro-electrical discharge machining. The machining parameters were systematically investigated and optimized to achieve high-precision micro-ball sockets when the k value was 0.98 and the initial layer thickness was 0.024 mm. Our method provided a new way to fabricate micro-ball sockets in C17200 with high efficiency for micro-liquid floated gyroscopes. [ABSTRACT FROM AUTHOR]

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]