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To meet the increasing demand for wire electrical discharge machining (WEDM) under extreme conditions such as ultra-high thickness cutting, micro-wire cutting, micro-energy finishing, and ceramic composites machining, a concept of multichannel discharge WEDM under semiconductor characteristics was proposed. The essence of this conception is that under these extreme machining conditions, the electrode wire or workpiece — or even both of the two electrodes — cannot be treated as electrically conductive materials of the conventional WEDM due to their high electrical resistance. However, they can exhibit electrical discharge behavior like semiconductors, which is defined as semiconductor characteristics. The conventional WEDM theory and related technologies cannot be applied to extreme WEDM because conventional WEDM only has one discharge channel per pulse, whereas multiple discharge channels can be generated by each pulse in extreme WEDM. Therefore, a suitable theory needs to be developed for extreme WEDM under semiconductor characteristics. Based on the multichannel discharge behavior of semiconductors, experiments were conducted on high-efficiency machining with multichannel discharge by stacking several workpieces as an assembly with semiconductor characteristics. It was proved that the multichannel discharge WEDM is capable of achieving high machining efficiency, as well as enhanced surface quality and lower wear of electrode wire. The proposed multichannel discharge WEDM sets up the foundation for the establishment of the theoretical system of EDM under semiconductor characteristics.

Wire electrical discharge machining (EDM) is the most important approach to cutting difficult-to-machine materials and components with complex shapes in the manufacturing industry. However, the multiple demands for high material removal rate, high surface quality, and low energy consumption require contradictory working conditions and restrict the further improvement of the performance of WEDM. This paper introduced a novel powder-mixed multi-channel WEDM method using the multi-channel discharge effect to meet the conflicting requirements. The multi-channel discharge effect utilizes the equipotential characteristics of the semiconductor powder mixed in the dielectric to disperse discharge energy and therefore provides a feasible solution to resolve the above contradictions. New working principles and machining mechanisms were discovered and verified by the simulation and experimental results. Comparative experiments show that the new powder-mixed multi-channel discharge WEDM method significantly reduced surface roughness and thermal defects while maintained a similar material removal rate as conventional WEDM.

This paper proposes a combined milling process of electrical discharge ablation machining (EDAM) and electrochemical machining (ECM) as an alternative to the low efficiency problem of less efficient electrical discharge machining (EDM) and to reduce the recast layer of EDAM. The working medium was a mixed aerosol of NaCl solution and oxygen, which has electrolytic and dielectric characteristics. The mechanism was analyzed: the combined milling process was a mixed process of EDAM, ECM, and EDAM-ECM combined machining. The EDAM-ECM combined machining can be divided into three stages: the electrolysis stage, discharge channel formation stage, and rapid ablative removal stage of metal substrate. Experiments were performed to compare conventional EDM milling, EDAM milling, and combined milling of EDAM and ECM. Results showed that the material removal rate (MRR) of the combined milling was 11.5 times that of EDM milling, and it increased by 18.7% compared with EDAM milling. The relative tool wear ratio (RTWR) decreased by 46.6%, and the thicknesses of the recast layer on the bottom and side were reduced by 61.2% and 49.2%, respectively, compared with EDAM milling.

Titanium alloy is widely used in aerospace and other industry fields because of its excellent physical and chemical properties. However, the fabrication process is still a challenge for the traditional machining processes due to the ultra hardness and chemical reactivity properties of titanium alloy. Electrical discharge machining (EDM) is a significant processing approach to machine titanium alloy regardless of hardness, while accompanied by disadvantages such as electrode wear and low machining efficiency. This paper proposed a novel mixed-gas atomization discharge ablation process (MA-DAP) method for high-efficiency machining titanium alloy with low tool wear. An atomized dielectric formed by a mixed gas, which mainly composed of oxygen and supplemented by nitrogen, and water medium was used in the machining process. The exothermic oxidation between the oxygen component in the atomized dielectric and high-temperature molten material activated by spark discharges could multiply accelerate material removal of workpiece. The explosive effect generated by the vaporization expansion of the water component in the dielectric would improve the machining quality and the processing capability of large depth-to-diameter ratio holes. To investigate the machining characteristics of the new approach, comparative experiments were conducted in terms of material removal rate, electrode relative wear rate, machining accuracy, surface morphology, and recast layer. The experimental results showed that, compared with traditional EDM, the material removal rate of MA-DAP was dramatically increased by more than an order of magnitude, and other technological indexes are greatly improved simultaneously. A deep-shaped blind hole with a depth-to-diameter ratio greater than 12 was obtained by the MA-DAP.

Severe uneven wire tension occurs during super-high-thickness (more than 1000 mm) cutting in high-speed wire electrical discharge machining, resulting in different discharge regularities between electrodes when the wire electrode is in the positive and negative traveling directions. Regarding the specific performance, a certain proportion of no-load pulses will appear between electrodes when the wire electrode is in the positive traveling direction, resulting in the feeding of the machine tool; when the wire electrode is in a negative traveling direction after feeding, a large number of short-circuit pulses will be formed, which seriously affect the continuous and stable feeding and the cutting speed. According to these different regularities, this work proposes the use of different reference objects as the basis of servo feeding in the positive and negative traveling directions. A pulse probability detection servo control method based on the discharge peak current is designed, and different control objects for the positive and negative traveling direction are used as the target probabilities of the proportional integral derivative algorithm. The results of experiments demonstrate that the proposed servo control method can significantly improve the cutting stability and cutting speed for super-high-thickness cutting. When cutting a workpiece with a thickness of 1000 mm, the surface machined by the average voltage detection-based servo method with the fixed threshold and the conventional pulse probability-based servo control method was found to exhibit obvious streaks, and the cutting speed was respectively 53.75 mm 2 /min and 63.6 mm 2 /min. Finally, the surface machined by the proposed servo control method was even, and the cutting speed was 77.78 mm 2 /min, thereby exhibiting an improvement of 44.71% as compared to that of the average voltage detection method with a fixed threshold, and the surface evenness was greatly improved. Thus, the proposed servo control method for super-high- thickness cutting was found to achieve a faster cutting speed and higher surface quality.

The electrical resistance of wire electrode increases with the decrease of the wire diameter. It is difficult to use the voltage threshold method to distinguish the spark and short-circuit states according to the discharge voltage, so it cannot meet the requirements of normal machining. In this study, a gap discharge state identification and servo control method based on discharge current are proposed in high-speed reciprocating microwire-EDM. The synchronous pulse can improve the stability of the system by reducing the disturbance of the discharge frequency and deionization. The experimental results show that a high wire speed is beneficial to the introduction of dielectric and the removal of erosion particles. When the target probability is set at 90%, the processing stability is higher. By using Φ 0.08 mm molybdenum wire electrode, the stable cutting of a 1250 height-diameter ratio (the ratio of cutting height to electrode wire diameter) workpiece is realized with an average cutting efficiency of 32.08 mm 2 /min. This study is a useful exploration of the machining of high height-diameter ratio workpieces by using a microwire electrode in high-speed wire-cut electrical discharge machining (HSWEDM).

Surface machined by high-speed wire electrical discharge machining (HS-WEDM) at super-high thickness (more than 1000 mm) cutting suffers from uneven surface, a major problem that has been investigated in this paper. According to the analysis, as wire frame span increases, the rigidity of the wire electrode decreases, and under the action of discharge explosive force, wire electrode vibration intensifies. As a result, the machining stability inevitably decreases. However, the core problem is whether there is enough working fluid in the slit to dampen and absorb the vibration of the wire electrode so as to ensure the positional stability of the wire electrode. To verify the above point of view: first, the wire guide and gravity take-up with bidirectional tension in the wire feeding system were installed to improve the positional accuracy of the wire electrode; second, to improve the flow of the working fluid into the slit, the slit width was increased by improving the working fluid and a medium carrier with a higher melting point and vaporization point can reduce the vaporization of the working fluid in the slit as much as possible. The experiment showed that the outlet flow of the improved working fluid is 56.72% higher than that of the original working fluid when cutting a 750-mm thick workpiece, which increases the damping and vibration absorption effect of the working fluid on the wire electrode in the long and narrow gap. After the above measures were implemented, super-high thickness cutting can be carried out continuously and steadily, the surface evenness was significantly improved, and the workpiece with a thickness of 2000 mm was cut successfully.

The vaporization of dielectric fluid between electrodes is very significant in high speed–wire cut electrical discharge machining (HS-WEDM) under high-energy conditions. Inter-polar corrosion products cannot be expelled in time, resulting in serious burn on the surface of the workpiece. To solve this problem, a certain proportion of kerosene is added to the dielectric fluid. The heat absorbed by kerosene chemical decomposition can effectively reduce the gasification of inter-electrode dielectric fluid. This ensures that there is sufficient dielectric fluid between the poles, and guarantees that the corrosion products produced between electrodes can be expelled in time, reducing the burn on the workpiece surface. Through theoretical calculation and comparative analysis, it is concluded that the heat absorbed by kerosene chemical decomposition is 24 to 211 times that absorbed by dielectric fluid gasification under the same volume condition. In this research, two cooling modes, kerosene chemical decomposition endothermic cooling and physical gasification endothermic cooling, are proposed. The important role of chemical decomposition endothermic cooling in inter-pole cooling is proved. The optimum proportion of kerosene in dielectric fluid is about 1%, as determined by experimentation. When the kerosene content exceeds 1%, carbon deposition will occur. When the kerosene content is around 1%, the cutting efficiency is 23% higher than that when kerosene is not added, and the burn area of the workpiece surface is reduced by 91%.

This paper analyzes the high-performance efficiency of atomized electric discharge machining (EDM) ablation using quantitative analysis of discharge and combustion erosion. Using an argon-atomizing medium and an oxygen-atomizing medium, a comparative experiment is performed to calculate the amount of material erosion generated by discharge and combustion during EDM ablation. Then, by collecting the single-pulse discharge waveform and the discharge rate, comparative experiments are carried out between EDM and EDM ablation to study the influence of electrical parameters on the ratio of discharge to combustion erosion in EDM ablation process. The reasons for the efficiency of EDM ablation are determined to be the higher discharge probability when compared to conventional EDM and the introduced oxygen which reacts with the activated material, increasing combustion effectiveness. The results show that under different pulse width, pulse interval, and average current experimental conditions, the combustion erosion in the atomization ablation process accounts for 67–78% of the total erosion, and the efficiency of atomization EDM ablation is over 8 times that of traditional EDM.

Tool wear inevitably occurs during electrical discharge milling (ED milling), adversely affecting the form precision of machined features. Specifically, radial tool wear negatively influences copying precision. In this study, electrical discharge ablation milling (EDA milling) with a microcutting depth was investigated to improve the machining precision of discharge milling. In the proposed method, the cutting depth of a single layer was kept at the micron level, which is smaller than the discharge gap, and the electrode was set to a fast feeding rate at a constant speed. The microcutting depth of a single layer made the discharge concentrate at the end of the electrode while avoiding the side. Under this method, radial tool wear is prevented to realize high-precision discharge milling. The discharge state and high-precision mechanism of the proposed method were analyzed. Contrast experiments were conducted to compare conventional electrical discharge milling (ED milling), conventional electrical discharge ablation milling with a large cutting depth (EDA milling with a large cutting depth), and EDA milling with a microcutting depth. Results indicated that when peak current was 30A (pulse duration was 150 μs and pulse interval was 120 μs), the machining efficiency of the proposed method (18.8 mm 3 /min) was 9.5 times that of ED milling (1.97 mm 3 /min) and was 62% higher than that of EDA milling with a large cutting depth (11.6 mm 3 /min). Besides, the surface quality and cross-sectional shape precision of the straight groove were significantly improved compared with EDA milling with a large cutting depth.