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This paper aims to enhance the machining characteristics of sinking electrical discharge machining by superimposing an impulse current on a conventional rectangular pulse. The material removal was found to be more significant when the time point of superposition was set earlier after the dielectric breakdown, as the plasma diameter is smaller. However, superimposition immediately after the discharge ignition leads to a higher tool wear ratio. Through experimentation and simulation, it was determined that the optimal time point to increase material removal while keeping tool wear low is approximately 12.5 μs when the rectangular pulse duration was 50 μs. [ABSTRACT FROM AUTHOR]

In die-sinking electrical discharge machining (EDM), it is challenging to implement internal flushing, mainly because it is easy to produce residual material columns on the workpiece cavity's bottom surface, affecting the processing quality and efficiency. In order to solve this problem, the internal flushing slotted electrode EDM technology was proposed. The slotted electrode was designed, and its preparation method was described. The influence of pulse width, pulse interval, and flushing pressure on the performance of the internal flushing slotted electrode EDM was studied using single-factor experiments. The experimental results indicate that, with the increase in pulse width, the material removal rate (MRR) increases first and then decreases, while the electrode wear rate (EWR) and the relative electrode wear rate (REWR) decrease gradually; with the increase in pulse interval, the MRR decreases, while the EWR and the REWR increase gradually; with the increase in flushing pressure, the MRR increases first and then decreases, while the EWR and the REWR increase gradually. When the slotted electrode is used for continuous internal flushing EDM, the appropriate pulse width, flushing pressure, and smaller pulse interval can improve the MRR and reduce the EWR and the REWR. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is one of the most broadly used non-traditional machining processes. The introduction of the idea of sustainable production and the need to adjust the ISO norms are essential for the assessment of all production methods using the principles of sustainability. The traditional EDM uses kerosene as a dielectric with poor safety and unfriendly environmental consequences. To solve this issue, the substitution of hydrocarbon dielectric is the principal consideration in EDM investigation. This research offers an intensive review of the environment-friendly EDM processes, where the objective is to try dielectric liquids that can be replaced, bypassing traditionally used EDM oil. It is seen that water- and gas-based dielectrics could assume control over synthetic oil in the EDM process. Revolutionary sustainable technologies using water or bio-dielectric have been introduced to rectify sustainability issues and have benefited greatly from the evolution of the EDM operation in terms of efficiency and sustainability. Innovative environmental-friendly EDM processes, which have determined the step of advancement in the field of scientific and mechanical research, are briefly discussed in this article. A blueprint of the forthcoming trends of the research is indicated in the last segment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The demand for higher efficiency in aircraft propulsion engines leads to materials with increasing thermomechanical strengths and new designs inducing filigree geometries of blisks and disks. Because of new designs which induce tighter tolerances, the high mechanical process forces in conventional cutting processes like broaching cause inacceptable geometrical deviations and high tooling costs. Due to the electro-thermal material removal mechanism, electrical discharge machining (EDM) ensures a force free and thus precise machining. The manufacture of fir tree slots in nickel-based alloys by wire EDM has been investigated in the last few years and the process was verified as an alternative technology for broaching. To get a better competitive position, the productivity can be prospectively increased by using an additional indexing rotary axis which ensures a precise and automated production of rotationally symmetric components and reduce production times, e.g., for the manufacture of fir tree slots on a disk. Nevertheless, the application of these axes cause changed flushing conditions and can also affect the electrical contacting as well. Both influence the process performance and demand a technology development or adjustment of standard machining technologies. The influence of these changed machining conditions has not been investigated scientifically to date. In this paper, the surface integrity and process performance of fir tree slots machined by wire EDM on the machine table are compared with the manufacture by using an additional indexing rotary axis. [ABSTRACT FROM AUTHOR]

Multi-axis electrical discharging machining (EDM) is the main manufacture method for shrouded blisks, which are key components of aero and rocket engines. Involving both linear and rotational axes, a feeding path for machining a narrow and twisted channel consists of a large number of G-code lines. Accelerations and decelerations at junctions, which connect two neighboring G-code lines, can significantly reduce the machining efficiency. In this paper, a new simplification of feeding paths in roughing EDM for shrouded blisks is proposed in order to reduce the number of junctions on a feeding path. However, deviating from the original feeding path, a simplified feeding path can bring over contour errors which can cause geometrical errors of workpieces. Contour error can thus serve as a criterion for simplifying the original path. Eight vertices of a hexahedron, which contains the electrode, are used to represent all points inside and on an electrode. Forward kinematics of a six-axis EDM machine is used to calculate the contour errors of the eight vertices when the electrode feeds along a simplified path. A simplified feeding path can be found provided that the contour error constraint is respected. Machining tests show that the use of a simplified feeding path in roughing EDM machining can reduce the average total machining time by 26.5% without significant impact on surface roughness and white layer thickness. [ABSTRACT FROM AUTHOR]

Difficulty in debris removal and the transport of fresh dielectric into discharge gap hinders the process performance of electrical discharge machining (EDM) process. Therefore, in this work, an economical low frequency vibration platform was developed to improve the performance of EDM through vibration assistance. The developed vibratory platform functions on an eccentric weight principle and generates a low frequency vibration in the range of 0–100 Hz. The performance of EDM was evaluated in terms of the average surface roughness (Ra), material removal rate (MRR), and tool wear rate (TWR) whilst varying the input machining parameters viz. the pulse-on-time (Ton), peak current (Ip), vibration frequency (VF), and tool rotational speed (TRS). The peak current was found to be the most significant parameter and contributed by 78.16%, 65.86%, and 59.52% to the Ra, MRR, and TWR, respectively. The low frequency work piece vibration contributed to an enhanced surface finish owing to an improved flushing at the discharge gap and debris removal. However, VF range below 100 Hz was not found to be suitable for the satisfactory improvement of the MRR and reduction of the TWR in an electrical discharge drilling operation at selected machining conditions. [ABSTRACT FROM AUTHOR]

Electrical discharge machining became a commercial process after the discovery of the importance of the dielectric fluid, which affects factors such as productivity and quality. Health, safety and environment are also important factors, particularly when oil-based fluids are used. This paper presents a literature survey on the use of dielectric fluids that provide an alternative to hydrocarbon oil. It has been reported that water-based dielectrics may replace oil-based fluids in die sink applications. Gaseous dielectrics such as oxygen may also be the alternative. Nonetheless, these need further research in order to be commercially viable. [Copyright &y& Elsevier]

In order to achieve high removal rate and low electrode wear in sinking electrical discharge machining (EDM) a stable machining process is required. The process stability is partly influenced by the contamination of the gap between the workpiece and the electrode. Additionally, it also depends on the size of the eroding surface at the given machining regime. When the eroding surface size varies with the depth of machining, the roughing regime has to be selected on-line. The work presented in this paper shows that the average discharge voltage depends on the eroding surface size. Through sets of experiments at constant machining parameters, varying size of the eroding surface and varying geometry of engaged surface were investigated. The average discharge voltages were calculated on the acquired electric voltage signals in the gap. The average discharge voltage is simple for on-line monitoring and it enables on-line detection of the eroding surface size as well as the on-line selection of the rough machining parameters. Thus the average discharge voltage depends on the geometry of the engaged surface, the prototype of the engaged surface has to be presented to the model for successful selection of the roughing regime as well. [Copyright &y& Elsevier]

In this paper, the machining phenomena in the electrical discharge machining (EDM) process are investigated through a new method of in-process measurement of gap distance. The aim of this study is to understand the cause of short-circuiting and to improve the machining rate. A pipe electrode is used and the working fluid is supplied to the gap space though a fixed restrictor and the pipe electrode. Since the pressure between the fixed restrictor and the tip of the pipe electrode (fluid pressure) depends on the gap distance, the absolute value of the gap distance can be determined in-process by measuring the fluid pressure. It is found that the gap distance at the moment when the short-circuiting occurs is more than several micrometers. This result indicates that the cause of the short-circuiting is the bridging of the gap space by collected debris. Based on these results, a new gap control method in which the gap distance is kept constant even when short-circuiting occurs is examined. [Copyright &y& Elsevier]

This research investigates the effect of machining parameters on material removal rate, electrode wear ratio, and gap clearance of macro deep holes with a depth-to-diameter ratio over four. The experiments were carried out using electrical discharge machining with side flushing and multi-aperture flushing to improve the machining performance and surface integrity. The machining parameters were pulse on-time, pulse off-time, current, and electrode rotation. Response surface methodology and the desirability function were used to optimize the electrical discharge machining parameters. The results showed that pulse on-time, current, and electrode rotation were positively correlated with the material removal rate. The electrode wear ratio was inversely correlated with pulse on-time and electrode rotation but positively correlated with current. Gap clearance was positively correlated with pulse on-time but inversely correlated with pulse off-time, current, and electrode rotation. The optimal machining condition of electrical discharge machining with side flushing was 100 µs pulse on-time, 20 µs pulse off-time, 15 A current, and 70 rpm electrode rotation; and that of electrical discharge machining with multi-aperture flushing was 130 µs, 2 µs, 15 A, and 70 rpm. The novelty of this research lies in the use of multi-aperture flushing to improve the machining performance, enable a more uniform GC profile, and minimize the incidence of recast layer. [ABSTRACT FROM AUTHOR]