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The increasing adoption of exotic and hard to cut materials in high-end applications makes electric discharge machining (EDM) process more relevant than ever. In particular, wire EDM variant (WEDM) deserves attention due to its ability to cut the workpiece's surroundings without completely evaporating the unused portion of the rare and expensive exotic materials. However, WEDM is a stochastic process that still lacks complete mathematical models and is driven by a myriad of parameters that will make its control a complex task. In WEDM, whenever the wire is fed too fast, the process will be interrupted not only by short circuits, but the wire electrode is most likely to break, jeopardising process efficiency in many ways. Currently, most of the literature has focused efficiency efforts in proposing a trade-off among parameters without a complete correlation with servo and control strategies. Therefore, this review aims to find and analyse the state-of-the-art approaches for controlling the Wire EDM process. A systematic literature review is conducted to identify and provide an adequate understanding of the best control strategies, fundamental parameters, and role. With no previous studies found, the present review focuses exclusively on servo control. First, it provides a comprehensive literature framework covering four decades, to next glimpse future developments of WEDM control strategies. Potential adoption of the findings can result in a deeper understanding of control variables and a broader and more efficient concept for WEDM servo feed control.

A micro rod machining method which can switch between electrical discharge machining (EDM) and electrochemical machining (ECM) by attaching/detaching a diode to/from a bipolar pulse generator in parallel to the working gap was newly developed using a wire electrode made of tungsten. The problem of the wire electrode wear was eliminated by the use of the wire electrochemical turning (WECT) method in which the tungsten wire electrode is continuously running. The ultra-short bipolar pulse current was generated by the electrostatic induction feeding method where a pulse voltage is coupled to the working gap through a feeding capacitance. The machining characteristics of three types of wire guide; disk-shaped WC guide, laminated wire guide and cylindrical acrylic guide, were studied. The experimental results showed that the cylindrical acrylic guide has the best machining characteristics without the influence of guide wear and with less stray current flowing through the working gap. Using the cylindrical acrylic guide, the influences of the feeding capacitance C1, and the total amplitude of the pulse voltage on the machining characteristics were studied. Finally, a stainless steel SUS 304 micro-rod with a high aspect ratio of 14 was fabricated efficiently by using the EDM and ECM modes for rough and finish machining in sequence with the same setup, pulse generator, and neutral electrolyte.

One advantage of a femtosecond laser is that it enables the processing of materials that are otherwise difficult to process via conventional methods such as cutting, grinding, electric discharge machining, etc. However, it is difficult to predict a three dimensional shape processed by the laser. To achieve required three-dimensional shapes using femtosecond lasers with high accuracy and efficiency, it is essential to develop a computer-aided manufacturing (CAM) system that generates processing data (NC data). In this paper, a simulation method is proposed for femtosecond laser processing, which is the basis for the development of a CAM system. A binderless nano-polycrystalline diamond is used as the workpiece material to test the proposed method. Based on a comparison with the experimental results, it is confirmed that the processing shape could be simulated at a high accuracy for fixed-point irradiation as well as scanning irradiation.

This paper proposes two new methods to observe discharge phenomena without interference from the plasma in electrical discharge machining. The first method uses a bandpass filter with a bandwidth of 800–820 nm and laser illumination with a wavelength of 800–820 nm. The second method also uses a bandpass filter with a bandwidth of 800–820 nm; however, in this method, the tungsten material is used not only as the tool electrode but also as the illumination source. First, the discharge process was observed using traditional methods to investigate the influence of the plasma on the observation of the discharge process. Then, the process of removing molten material from both the tool electrode and workpiece, as well as molten pool movement, was observed using the first method proposed in this paper. The material removed from the tool electrode was scattered upward along the end profile of the tool electrode, while the material removed from the workpiece was distributed along the horizontal direction. To explain these phenomena, the flow distribution in the gap was qualitatively analyzed using a fluid simulation. Finally, the discharge process was also observed using the second method proposed in this paper. A tungsten tool electrode can emit light with a wavelength of 800–820 nm, which shines on the observed region during the discharge process. The observation results verified the phenomenon of multiple explosions of the molten pool during the discharge process. Moreover, it was found that the material removed by the explosion of the molten pool was scattered in different directions and hardly influenced by the flow distribution in the gap.

Honing processes require a systematic preparation and a regeneration of the honing tool to guarantee a sufficient cutting behaviour and prevent unintended wear of the tool. These dressing processes are particularly important for the regeneration of the macro- and microscopic topography of the honing stones. The established method of manual shaping subsequent to a cylindrical grinding process demands a high skill level, a great amount of non-productive time and is not reproducible. In this paper the preparation of honing stones by use of electrical discharge machining (EDM) is presented. The aim is to ensure an automatic, systematic and reproducible process of resetting the bond of honing stones. Different tool electrode materials were analysed systematically for two different bond specifications of the honing stones. EDM process parameters were studied within a design of experiments (DoE) strategy and a subsequent effect analysis to assure the identification of most appropriate EDM process parameters. After this procedure various cycles of long-stroke honing processes were carried out. As a result, the new approach makes it possible to prepare honing stones with reproducible sharpness and macroscopic topography within an automated process. The dressing time td was reduced by 88 % compared to the established method.

In electrical discharge machining, both the gas and liquid dielectric have unique advantages and inevitable disadvantages. The mist medium with a special property between gas with liquid is expected to have a better performance in EDM. In this paper, the performance of mist deionized water jet has been studied based on the disadvantages of deionized water in deep micro hole drilling: electrolysis action, electrophoresis action and gap-contamination by debris. Based on the analyzation on the advantages of mist jet, three projects of experiments have been done to verify its performance on the suppressing of electrolysis action and improving the debris exhaust. The results show that the micro EDM drilling with high machining speed and accuracy can be realized with mist jet. This method is particularly effective in deep micro hole drilling, since deeper holes can be obtained at faster machining speed with mist jet due to its significant improvement in debris exhaust.

Water-repellent surfaces have recently become an active area of research due to the desire to achieve self-cleaning, anti-sticking, and non-wetting properties on surfaces. These surfaces are required for different engineering applications. A superhydrophobic (SHP) surface achieves a water contact angle (CA) of 150° or greater. The physical understanding of the process by which surfaces attain superhydrophobicity is still limited, making it difficult to fabricate such surfaces by machining due to the hierarchical scale of the features involved. This work, therefore, aims to shed light on the physical understanding of the behaviour of a water droplet as it rests on a micro textured surface. In the first part of the work, a mathematical model is developed that follows a basic and novel approach of force balance considering a water drop sitting on a surface under static conditions. The various forces responsible for equilibrium are individually evaluated. The model used to describe a surface's interaction with water establishes the relationships between various parameters in the force balance system. From these relationships, the water contact angle (CA) required for superhydrophobicity was found through a simulation. In the second part of this work, arrays of projected micro-features were fabricated on different materials using deep X-Ray lithography (DXRL), micro wire EDM, and the wire wound method. The measured values of the CA on the fabricated surfaces were similar to the values obtained from the model. The proposed model, therefore, helps in designing SHP surfaces (SHSs) on large-scale arrayed micro-features based on several geometrical parameters.

In today's continuously growing demand for components with increasingly smaller dimensions and features, micro milling is gaining more significance. However, for the mass production of components with micro features, injection molding is still customary in order to keep target costs. Due to high requirements regarding lifetime and resistance to wear, the molds are made of hardened steel. The shaping of those molds involves electrical discharge machining (EDM), because the process is independent of the material hardness. As a work tool for EDM, electrodes made of pure copper (Cu) and tungsten reinforced copper (WCu) are commonly used. The quality and reliability of the eroded shapes are determined to a high extent by the quality of the electrode deployed. For this reason, micro milling is a crucial factor in the process chain and its impacts have to be evaluated. This paper explores the key factors which have to be considered in micro milling pure copper and tungsten reinforced copper for micro features of electrodes. Due to scaling effects, micro milling differs strongly from macro milling. For mastering this process, a new approach to identify cutting edge geometry and the influence of the common milling parameters and material properties is required. Two flute micro milling tools with diameters as low as 200 μm and a cutting edge as low as 3 μm are applied for examination. To generate suitable cutting conditions with such small tools, extremely high rotational speeds of the spindle are required. Here it is chosen to be 200.000 rpm. The size of the minimum uncut chip thickness for both materials is discussed. Optimal process parameters and conditions for micro machining both materials are derived concerning process forces as well as burr and wear formation.

Micro electrical discharge machining (micro EDM) provides an alternative in generating complex 3-D micro features in difficult-to-machine materials. The micro EDM performance depends not only on machining parameters but also on the microstructures and micro-characteristics of materials. The effect of free surface layer of austenitic stainless steel on the micro EDM performance is investigated in this paper. Experiments are carried out by machining multilayer stainless steel workpieces without and with surface treatment (acid pickling and oxidation treatment). Surface layer model is built to demonstrate the increasing influence of surface layer on micro EDM performance when the size of workpiece is decreased. The surface free energies of AISI 304 workpieces are estimated by measuring the contact angles. The results show that the steel workpiece with oxidation treatment has the highest surface free energy and the highest material removal rate compared with those without treatment and with acid pickling treatment. The influence of surface layer of steel workpiece on micro EDM performance is more significant when the discharge energy is lower due to size effects. Taper ratio of machined holes on steel workpiece without treatment is much higher than those of holes on steel workpieces with acid pickling and oxidation treatment. As a conclusion, surface treatment of steel workpiece before machining is an effective method to improve the machining efficiency and machining precision of micro EDM, especially when involving the sub-micro or nano-machining where machining is conducted on the workpiece surface.

This paper studies influence of and optimizes pulse-on time, pulse-off time, servo voltage, and feed rate of wire on microgeometry and surface finish of stainless steel meso-helical gears (MHG) and meso-bevel gears (MBG) manufactured by wire spark erosion machining (WSEM) process. Microgeometry of MHG was evaluated in terms of error in total profile and total cumulative pitch and that of MBG in terms of error in single pitch and total cumulative pitch. Average and maximum surface roughness values were used to evaluate their surface finish. Twenty-nine experiments with two replicates were conducted using Box-Behnken approach of response surface methodology thus manufacturing 58 meso-helical gears and 58 meso-bevel gears. It was observed that higher pulse-on time and servo voltage, and lower pulse-off time and feed rate of wire yield poor microgeometry and surface finish of MHG and MBG. Desirability function analysis based multi-response optimization was used to identify optimum WSEM parameters to manufacture the best quality of MHG and MBG. The optimized values of the responses were validated experimentally. It was found that WSEM can attain up to DIN 6 quality in microgeometry of MHG and MBG. SEM micrographs of the best quality MHG and MBG revealed accurate and uniform bore, tooth profile, flank surfaces free from burrs and sharp edges and without any undercut at root. Microstructural examination of these gears showed flank surfaces free from cracks, globules and pores. This study proves that WSEM is economical and technically superior process for near net-shape manufacturing of high quality MHG and MBG.

In micro-electrical discharge machining (micro-EDM), the minimum machinable size is determined by the material removal per pulse discharge. In this study, two types of single-crystal silicon tool electrodes with high electrical resistivity were used to fabricate the micro-rod by minimizing the material removal per pulse discharge, and to reduce the machinable size for micro-EDM. The EDM characteristics of micro-rods using silicon tool electrodes with high electrical resistivity were investigated. Based on the experimental results, it is found that the peak discharge current decreases with an increase in the electrical resistivity of the tool electrode. Consequently, the average diameter of discharge craters generated on the micro-rods is reduced to approximately 0.4 μm. The silicon tool electrode has also disadvantage of their higher tool wear ratio compared with that of copper, which is probably due to the brittleness of the silicon. Moreover, the material removal rate is significantly lower for the silicon tool electrodes compared with that for the copper tool electrode. Because the average diameter of the discharge craters generated by the silicon tool electrodes is small, an attempt is made in this study to fabricate a cemented tungsten carbide micro-rod with a diameter less than 1 μm using the silicon tool electrode with an electrical resistivity of 1.2 × 10−3 Ω m. The result is indeed promising since the diameter of the micro-rod is 0.8 μm, indicating that it is possible to fabricate micro-rods with a diameter within the sub-micrometer range by only using silicon tool electrode with high electrical resistivity in micro-EDM.

In wire electrical discharge machining (WEDM), there are inevitable phenomena of wire deflection and vibration because wire electrode is slender and flexible, and these phenomena are closely related to workpiece surface quality and geometric accuracy. Besides, the phenomena of wire deflection and vibration have a direct relationship with wire tension. In this paper, a high-precision constant wire tension control system is built to restrain wire deflection and vibration so as to improve workpiece surface quality and geometric precision. Firstly, the factors resulting in wire tension fluctuation are briefly introduced. Additionally, the constant wire tension control system is designed on the basis of the structure improvements of wire winding system and closed-loop control. And then, the high-precision transfer function of this control system is deduced by the method of system identification, and three intelligent algorithms are utilized to tune the parameters of PID controller. Next, the wire tension control experiment and cutting experiment are carried out to evaluate the performance of this control system. Experiment data indicate that this control system has good ability of controlling wire tension without obvious overshoot. In addition, it is proved that this control system can obviously improve workpiece surface quality and geometric error, such as surface topography, cutting kerf width, corner error and taper cutting error. This proposed constant wire tension control system is worthy of popularization and application in practical manufacturing field.

This paper shows that the radial flow caused by the collision of the metal vapor jets generated from the surfaces of the tool electrode and workpiece serves as one of the material removal mechanisms in electrical discharge machining (EDM). Material removal per single discharge of a steel workpiece was larger using the tool electrode made of materials with lower boiling point. Observation of the discharge gap using a high-speed video camera showed that molten material on the workpiece was swept away more significantly and larger amounts of debris was removed using the tool electrode materials with lower boiling point. The molecular dynamics simulation showed that the radial velocities of the vapor atoms removed from the workpiece were higher using the tool electrode with lower boiling point because the jets from the tool electrode were more intensive. Furthermore, the discharge reaction force acting on the wire electrode in a single pulse discharge in air was measured from the wire vibration. The results showed a larger discharge reaction force using a zinc coated brass wire compared with a non-coated wire. Thus, it can be concluded that the shear force caused by the jets serves as one of the material removal mechanisms in EDM. Furthermore, one of the reasons for the higher material removal rate obtained using zinc coated wire electrode in wire EDM is the ease of boiling of the zinc coating layer on the wire surface.

Using molecular dynamics simulation (MDS), investigation was carried out to understand the mechanism of material removal during the formation of overlapping craters on surfaces obtained by micro electrical discharge machining (MEDM) and their effect on the crater surface. Apart from overlapping craters, two other cases were also considered viz. craters separated by a finite distance and craters coinciding at the periphery since these two will mostly occur during initial phase of machining. In all cases, the material removal was due to melting and vaporisation; it was also observed that the amount of material removal by vaporisation increased from 36% (approx.) in 1st discharge to 44% (approx.) in the 2nd discharge due to ease of vaporising the amorphous layer formed after the 1st discharge. Moreover, final crater size viz. depth and diameter obtained in the 1st crater measured at the end of MDS was relatively less as compared to 2nd crater. The increase in crater depth and diameter increased with reduction in distance between discharges. The increase in diameter of 2nd crater with respect to 1st crater for all the three cases was observed both during MDS and on the actual surface generated by MEDM.

A new method, wire electrochemical grinding(WECG), is proposed for machining tungsten micro rods with neutral electrolyte and bipolar current. The inevitable problem of tool wear due to the bipolar current can be eliminated by using a running wire as the tool electrode with this method. In this study, three kinds of wire guides were used for feeding the workpiece rod in the axial direction: cylindrical cemented tungsten carbide (WC) guide, cylindrical zirconium oxide (ZrO2) guide, and disk-shaped cemented WC guide, to investigate the influence of materials and configurations of the guide on the machining characteristics. The experimental results showed that the disk-shaped WC wire guide can realize higher machining accuracy because of less influence of stray current flowing through the gap formed between the machined micro-rod and wire guide. Even if the ZrO2 material has a much lower electrical conductivity than that of the cemented WC, the machining process was still influenced by the stray current between the micro-rod and wire guide. Furthermore, micro-rods were also machined by feeding the rod workpiece in the radial direction. Compared to when the workpiece is fed in the axial direction, the current was higher, which was clarified by the simulation of the current density distribution. However, the machining time was much longer than that with the workpiece fed in the axial direction because more machining steps were necessary to obtain a smooth side surface. With the workpiece fed in the axial direction method, a tungsten micro-rod of 35 μm in diameter was machined to the length of 163 μm. The results confirmed that the new method is capable of miniaturization equivalent to micro electrical discharge machining (EDM).

Recently, a multi-wire electrical discharge slicing (EDS) process has been proposed for slicing SiC ingots into wafers. A significant reduction in kerf loss is expected with this method compared with the conventional multi-wire saw method. However, this process entails a high risk of wire breakage. Therefore, in the present study, a novel electrical discharge slicing process utilizing a running ultra-thin foil tool electrode is demonstrated for the slicing of SiC ingots. Relative to multi-wire EDS, the risk of tool breakage can be reduced with this new technique by increasing the tool cross-sectional area. A 25-mm (1-inch) SiC ingot was successfully sliced with the proposed method and a kerf loss of about 100 μm was achieved by utilizing a foil tool electrode with a thickness of 50 μm. This paper summarizes the specific characteristics and results of this process, including the machining stability, machining strategy, selection of foil tool material and multiple simultaneous slicing.

The application of integral shrouded blisks improves the aerodynamic efficiency and reliability of aerospace engines, while their semi-closed geometrical structures, high blade profile accuracy and difficult-to-cut material properties bring great challenges to their manufacturing. Electrical discharge machining (EDM) is regarded as an effective way to produce this kind of parts. In this paper, an electrode design method for EDM machining of integral shrouded blisks from a primitive electrode by electrode size reduction and electrode division was described. A new electrode feeding planning method named maximum free distance was presented, in which the position and attitude of a new electrode feeding path node was optimized by maximizing the distance that the electrode is able to move along a predefined reference direction before it interferes with the blisk. The feeding path sparsification was conducted to improve the workpiece debris evacuation and to save the machining time. The example of EDM machining an integral shrouded impeller with 1 in 2 out flow channels was given to validate the proposed electrode feeding path planning method.

Machining of high-aspect ratio slots is a common operation in industry, particularly in the mold and die and aerospace sectors. Electrical Discharge Machining (EDM) is a competitive technology for this operation, since it does not depend on material hardness and can fulfill strict geometrical requirements. However, due to debris accumulation in the narrow gap, the machining depth for stable machining is limited. The present work includes original findings about the influence of machined holes on flushing efficiency. Different configurations for this basic approach have been proposed and their performance discussed in terms of machining time and electrode wear. A remarkable and original finding is that continuous pockets or open holes are much better than the separated or closed holes. Furthermore, the paper shows that a sudden change in material removal rate occurs when the vacant spaces of the holes are sunk in the slot. A deeper insight into the EDM phenomena has been achieved through a study of discharge parameters, by analyzing discharge frequency, duty factor, discharge delay time and discharge off-time. In this study, using the proposed electrode reduced the process time by as much as 65% in the machining of 10 mm depth slots. Moreover, machining stability can be guaranteed if the flushing pockets machined on the electrode go through the whole depth of the machine.

Dielectric, such as kerosene-based oil, deionized water or air, is an essential part of electrical discharge machining (EDM). It directly influences machining performance of the EDM process. While there is large tool electrode wear during machining in liquid dielectric, micro EDM in gas dielectric exhibits almost no tool electrode wear. However, small discharge energy, low dynamic viscosity and low debris concentration of micro EDM in gas creates narrow discharge gap, causing frequent occurrence of abnormal discharge. In this paper, nitrogen plasma jet (NPJ) is used as a dielectric to increase the discharge gap of micro EDM in gas. The machining characteristics of micro EDM in NPJ are investigated and compared with those in other dielectrics. It was found that the discharge distance, machining efficiency and surface quality are significantly improved in NPJ, compared to those in gas under the same conditions. The coaxial high-velocity air jet is helpful to reduce short circuits. Experimental results reveal that NPJ is a viable dielectric in micro EDM.

Micro electric discharge machining (μ-EDM) is a widely used process for machining of difficult to machine materials. The occurrence of arcing and short circuiting in micro electric discharge drilling (EDD) is a common problem which limits the aspect ratio achieved during the process. The present study is focused on the improvement in response characteristics by eliminating the occurrence of arcing and short circuiting. These problems can be addressed by modifying the tool electrode geometry. Although, EDD using shaped tool electrodes improve response characteristics as proven by the previous studies, but time spent in electrode fabrication must also be considered as it affects the overall productivity. Considering the literature related to EDD using shaped tool electrodes, the proposed electrode has been found to have minimum electrode fabrication time i.e. 9 min for an electrode length of 3.2 mm. Therefore, the proposed electrode is capable of producing holes of high aspect ratio with minimum electrode fabrication time. The proposed electrode was also found to be effective in eliminating the accumulation of debris in the machining zone. Moreover, the need of flushing during the process has been totally eliminated making it a self-flushing electrode. The mechanism of removal of debris is well explained based on the images captured using a high speed camera. The performance of the proposed electrode was evaluated with respect to response characteristics such as material removal rate, tool wear rate, aspect ratio, taper angle and corner radius of the drilled hole. A substantial increase of 300% in aspect ratio was recorded using the designed electrode as compared to the solid cylindrical electrode for the hole diameter of 0.8 mm.

Nano-finishing of a material surface is one of the most required properties in industry. There is high need of nano-finishing of diamagnetic materials such as copper and its alloys in electronic industries and electrode of electric discharge machining. Some industries like laser, aerospace, dentistry and metal optics etc. widely use highly finished copper mirrors. As copper is soft and chemically reactive material, its surface finishing at nano level is a difficult tasked. To fulfill this need, a new magnetorheological technique for precise surface finishing of diamagnetic materials has been conceptualized. Two cylindrical permanent magnets along with magnetorheological polishing fluid have been used to finish the diamagnetic copper alloy workpiece. The cylindrical permanent magnets tool with magnetorheological polishing fluid at its tip surface is rotated over the copper alloy workpiece surface and performs finishing by the stiffened magnetorheological polishing fluid. The permanent magnets finishing tool along with magnetorheological polishing fluid at its tip surface and diamagnetic copper workpiece have been modeled as well as simulated in Maxwell Ansoft V13 (student version) software. Distribution of magnetic flux density in the working gap is obtained and analyzed. Experiments are performed on the copper alloy workpiece and least Ra value of 28.8 nm is achieved in finishing time of 7.5 min from its initial value of 273.6 nm. Surface characteristics of both polished and unpolished workpiece are analyzed with the scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results obtained from finite element analysis and experimentation assures that the new design of magnetorheological finishing tool using permanent magnets is capable to nano-finish of diamagnetic materials such as copper alloy etc.

The friction force developed in the demolding phase of the micro injection molding process is mainly determined by mold surface finish, which affects the tribological phenomena occurring at the polymer–tool interface. In this work, the effects on the ejection force of two cavity surfaces machined with different technologies (viz. micro milling and micro electro discharge machining), but with similar value of Ra , were investigated. The relations between different surface topography parameters and the ejection force were then analyzed, in order to identify the parameters that most appropriately describe the friction at the polymer–tool interface. The experimental results showed the strong interactions between the mold surface texture and the micro injection molding process parameters that promote the replication, such as mold temperature and holding pressure. The different machining technologies generated two mold textures that have a similar value of Ra , but their influence on friction can be properly described only using several other surface topography parameters.

Electrical discharge machining by foil electrode serves as an alternative method for SiC slicing. This technology uses a highly tensioned thin foil as the tool electrode. The main advantages over wire EDM are that the foil thickness can be made smaller than the wire diameter, vibrations can be avoided by applying high tension, and higher current can be supplied since there is less risk of tool breakage. However, due to the large side surface area of the foil electrode, there is a high occurrence probability of side surface discharges and high concentration of debris, which affects kerf width accuracy and machining stability. In the aim to overcome both problems, this study proposes two foil electrode designs: a foil electrode in which holes are machined and the insulation of the side surface areas by a resin coating layer of 5 μm thickness. The influences of both foil electrodes were tested with three different slicing strategies: no strategy, applying jump motion of the tool electrode, and applying reciprocating motion. From machining experiments and comparative studies of the discharge delay time, it was found that with both foil tools, the occurrence probability of side surface discharges can be reduced. In addition, the chip pocketing effect of the holes enhance the flushing conditions, resulting in a higher cutting speed.

A serious limitation of sink electrical discharge machining is the rapid geometric degeneration of sharp features due to localized wear. Electro-erosion edge honing is a novel process that creatively exploits this phenomenon for the edge preparation of cutting tools. This paper presents a geometric model of the process that can accurately predict the profiles of both symmetric and asymmetric edges that are prepared in the process. Numerical simulation of the model quantifies the concept of relative duty in the context of the process, and offers unique insights into process mechanisms. In particular, the critical influence of the wear ratio in determining the prepared edge being either rounded or chamfered is clarified, in consideration of the trajectory of successive discharge trains. The work further enables an understanding of the influence of initial edge defects on the processed edge, and presents guidelines for optimizing edge quality.

In micro electrical discharge machining (EDM), because the material removal per single pulse discharge mainly determines the minimum machinable size of a micro EDM, decreasing the material removal per single pulse discharge is important. In this study, in order to decrease the material removal per single pulse discharge, high electric resistance materials such as single-crystal silicon are used for electrodes. Analytical results show that when the electrode resistance increases, the peak value of the discharge current decreases, whereas the pulse duration increases. In addition, the discharge energy decreases when increasing the resistance. Silicon is used as a tool electrode, and the effect of resistivity of the silicon tool electrode on the diameter of discharge craters generated on the stainless steel workpiece is examined. Experimental results reveal that with increasing silicon electrode resistivity, the diameter of discharge craters decreases. Because the diameter of discharge craters can be decreased to 0.5 μm, improved finished surfaces of R z 0.03 μm are obtained.

The tool electrode has a significant role in electrical discharge machining (EDM) performance, as it affects machining efficiency, surface quality and the geometrical accuracy of the machined component. This study presents a new approach for developing a pure copper electrode using severe plastic deformation (SPD) to enhance the machining characteristics during EDM. Equal channel angular pressing (ECAP) is selected because it is the most successful SPD method of processing bulk materials. Finite element analysis, microstructural assessment as well as nanoindentation tests are carried out to determine the behavior of pure copper after one and two ECAP passes. The effectiveness of EDM when using ECAP-treated electrodes is evaluated by introducing new techniques of measuring the volumetric overcut (VOC) and corner sharpness. In addition, tool wear rate (TWR), material removal rate (MRR), electrode wear ratio, surface roughness, surface crack density and the critical crack zone are studied. The results emphasize that an electrode subjected to one pass of ECAP can enhance the workpiece accuracy by decreasing the VOC and increasing corner sharpness by 13 and 66%, respectively. It is also revealed that the nanohardness enhancement following ECAP leads to lower TWR and electrode wear ratio. An investigation of the surface characteristics indicates a thinner recast layer is achieved when using one ECAP pass-treated electrode, which leads to 26% lower surface crack density.

Electrical discharge machining (EDM) is a non-conventional machining technique for removing material based on the thermal impact of a series of repetitive sparks occurring between the tool and workpiece in the presence of dielectric fluid. Since the machining characteristics are highly dependent on the dielectric’s performance, significant attention has been directed to modifying the hydrocarbon oil properties or introducing alternative dielectrics to achieve higher productivity. This article provides a review of dielectric modifications through adding powder to dielectric. Utilizing powder mixed dielectric in the process is called powder mixed EDM (PMEDM). In order to select an appropriate host dielectric for enhancing machining characteristics by adding powder, a brief background is initially provided on the performance of pure dielectrics and their selection criteria for PMEDM application follow by powder mixed dielectric thoroughly review. Research shows that PMEDM facilitates producing parts with predominantly high surface quality. Additionally, some studies indicate that appropriate powder selection increases machining efficiency in terms of material removal rate. Therefore, the role of powder addition in the discharge characteristics and its influence on machining output parameters are explained in detail. Furthermore, by considering the influence of the main thermo-physical properties and concentration of powder particles, the performance of various powder materials is discussed extensively. Since suitable powder selection depends on many factors, such as variations in EDM, machining scale and electrical and non-electrical parameter settings, a thorough comparative review of powder materials is presented to facilitate a deeper insight into powder selection parameters for future studies. Finally, PMEDM research trends, findings, gaps and industrialization difficulties are discussed extensively.

The concept of electrochemical discharge machining (ECDM), also known as electrochemical spark machining (ECSM), was presented for the first time in 1968. Since then, this technology remains as research topic and was never explained seriously for industrial applications. The ECDM is a non-traditional machining technology used for machining of electrically non-conducting materials like glass, ceramics, quartz, etc. The literature reveals that the concept of mechanism of material removal in this machining process is not yet understood well. However, phenomena involved in the material removal needs to be investigated well in order to improve the process. In this paper, the concept of mechanism of material removal in ECDM is reviewed till date; scopes for further research have been identified. Possible future efforts to enhance the material removal rate in ECDM are also discussed.

In this investigation, response surface method was used to predict and optimize the material removal rate and tool wear ratio during electrical discharge machining of AISI D6 tool steel. Pulse on time, pulse current, and voltage were considered as input process parameters. Furthermore, the analysis of variance was employed for checking the developed model results. The results revealed that higher values of pulse on time resulted in higher values of material removal rate and lower amounts of tool wear ratio. In addition, increasing the pulse current caused to higher amounts of both material removal rate and tool wear ratio. Moreover, the higher the input voltage, the lower the both material removal rate and tool wear ratio. The optimal condition to obtain a maximum of material removal rate and a minimum of tool wear rate was 40 μs, 14 A and 150 V, respectively for the pulse on time, pulse current and input voltage.

Electrical discharge machining (EDM) is one of the most promising non-traditional micro-scale machining methods. Because several operating parameters that are insignificant in macro EDM cannot be neglected during micro EDM process, models derived from the macro EDM process may be inappropriate at the micro scale. This paper contains a comprehensive review of size effects in traditional micro-machining and characteristics specific to micro EDM compared to macro EDM techniques. The very concept of size effects in micro EDM is thoroughly defined and three categories of effects are presented: material microstructure, processing parameter and thermal conduction size effects. Future potential research directions on the subject are also summarized. We assert that careful research and precise attention must be given to size effects in micro EDM. Size effect information especially benefits the machining speed and machining precision of micro EDM.

The present article describes a method for enhanced accuracy in machining components produced on CNC wire-cut electrical discharge machines. In this method, machining programs are generated on the basis of nominal geometric models of the produced objects, developed in CAD/CAM systems. After the initial machining, coordinate measurements are performed. On the basis of these measurement results, the values and distribution of the machining deviations are determined. The obtained information is then used to modify the nominal geometric models of the produced objects and to correct the machining programs. After that, the machining process and measurements are repeated. The method described in the present article was verified using the example of a curvilinear profile, produced with the use of a wire-cut electrical discharge machine.

A turn-milling machine, which is a device having two spindles that rotate a tool and workpiece, can be used to fabricate various shapes by cutting. However, little progress has been made in microcutting using a turn-milling machine. Therefore, a micro turn-milling machine designed especially for microtools was developed and used to fabricate micropins with various cross sections. Cemented tungsten carbide microtools, which are useful both as a milling cutter and as a turning tool, were processed by electrical discharge machining and employed for microcutting. As a result, various micropins were successfully fabricated, including not only cylindrical pins but also those with cross sections having square, triangle, and cross shapes. These noncylindrical micropins have the smallest reported cross-section dimensions for pins fabricated by cutting to the best of our knowledge. Furthermore, cutting characteristics such as the machined shape and surface quality were investigated, which showed that better micropin shapes were obtained by up-cut turn-milling than by down-cut turn-milling or by turning. In contrast, turning was superior to turn-milling in terms of the surface quality.

This paper presents a new approach for the recording of the total quantity of energy exchanged during the micro electrical discharge machining (EDM) process. In particular, this approach allows for the estimation of the percentage of energy absorbed by the two electrodes (tool and workpiece) using a combination of theoretical models and experimental results, thanks to an advanced discharges measuring approach. An experimental campaign was executed on a Sarix SX200 micro-EDM machine with a tungsten carbide tool electrode. In particular, the process was analyzed for two different electrode shapes, a triangular and a rectangular based parallelepipeds, and two sets of machining parameters. After the execution of the experimental campaign it estimate the total amount of energy that occurred during the entire die sinking process. The energy effectively lost into the tool, into the workpiece and into the dielectric was estimated from the measurement of the volume of material actually removed both from the tool and from the workpiece. The preliminary results appears to fit those presented in the literature and the validity of several theoretical crater models was then assessed. The validation of the presented acquisition method could enable the use of information related to energy repartition in the simulation of the micro-EDM process. The reported research was partly funded by the Engineering and Physical Sciences Research Council (EPSRC) under the grant EP/J004901/1.

The most used processes for generation of high aspect ratio microchannels are Nd: YAG laser technology on silica substrate and ultra violate lithography (UV-LIGA) process on metals. There are a few micromachining technologies such as micro mechanical milling, micro electro discharge machining (EDM) and electrochemical micromachining (EMM) for production of high-aspect-ratio micro features on highly stressed and anticorrosive metal like stainless steel. This paper discusses the micro fabrication of high aspect ratio micro features at the intended location on high strength stainless steel sheet of very small thickness to high thickness with highest average aspect ratio 14.33 achieved during microchannel generation by EMM with the help of coated microtool. Mathematical model relating aspect ratio with various parameters and machining conditions is derived to explore the ways to increase the aspect ratio of micro features. Experimental investigations were carried out to know the effect of vibration of microtool, frequency of pulsed voltage, microtool tip shape, thickness of work piece and non-conducting layer coated microtool on high aspect ratio micro features. Vibration of microtool with very small amplitude improved the stability of micromachining due to improved flow of electrolyte.