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(a) SEM images showing recast layers on workpiece after EDM (b) SEM images showing micro-cracks on workpiece after EDM
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Electric Discharge Machining is one of the most accurate unconventional manufacturing processes used for cutting or creating intricate shapes in very hard or difficult-to-cut, electrically conducting materials. The adoption of tool rotation methodology increases the material removal rate by increasing the spark efficiency and effective debris clear...
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Context 1
... the machining process is over. They comprise of the workpiece material, tool material and the decomposed carbon from the dielectric. Since it consists of tiny particles which are solidified on the surface of the material at high temperature, therefore, the hardness of these layers is more than the hardness of the base material. SEM images in Fig. 5 (a) clearly show the recast layer deposited over the AISI D3 steel surface after rotary and stationary tool EDM. It can be clearly seen from the figure that the rotary tool EDM has very thin recast layer as compared to the stationary tool EDM. The average recast layer thickness in the case of rotary EDM process is around 2 to 25 µm, ...
Context 2
... Surface Micro-cracks: These cracks are present on the primary surface of the workpiece after machining. They occur on the surface once the resettled material on the surface gets solidified and during the process get cracked at various places. SEM images of Fig. 5 (b) shows the micro-cracks for rotary and stationary tool EDM. We can observe that the surface obtained through rotary EDM has very fewer cracks as compared to the surface obtained through the stationary one. (a) Surface Roughness: The surface roughness was measured using the Optical Profilometer. The average surface finish (Ra value) ...
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Citations
... With regard to overcoming some shortcomings of traditional EDM method, some modifications have been introduced in tool electrodes e.g. using a rotating electrode. The rotary EDM is a hybrid EDM method to shows some prospectus in attaining higher MRR and better surface finish over conventional EDM process [6][7][8]. Some of the authors stated the advantages of Rotary EDM while machining difficult to cut materials such as En41b nitride steel [8], EN-8 steel [6]AISI D3 steel [7,9]. ...
... The rotary EDM is a hybrid EDM method to shows some prospectus in attaining higher MRR and better surface finish over conventional EDM process [6][7][8]. Some of the authors stated the advantages of Rotary EDM while machining difficult to cut materials such as En41b nitride steel [8], EN-8 steel [6]AISI D3 steel [7,9]. Dwivedi et al. reported that rotation of EDM tool while machining of AISI D3 steel improves the surface finish of machined surfaces [7]. ...
... Some of the authors stated the advantages of Rotary EDM while machining difficult to cut materials such as En41b nitride steel [8], EN-8 steel [6]AISI D3 steel [7,9]. Dwivedi et al. reported that rotation of EDM tool while machining of AISI D3 steel improves the surface finish of machined surfaces [7]. Further, Pandey et al. [9] proved through experimental work that rotary copper-tool tool yielded high MRR and surface finish and low TWR. ...
... The material is removed at a controlled rate as fine particles in the workpiece. The dielectric discharges material from the fusion cavity when the electrode is pushed upwards in due course [40]. a) During the procedure, the workpiece and instrument are never in contact, and a little gap between the electrodes isolates them. ...
In this world of advanced technology., unconventional Micro-EDM technology has shown extraordinary interest in the development of microstructure. This work presents the development of the Die Sink EDM machine and investigates the relation and effect of melting point of the electrode materials on Material Removal Rate (MRR) by machining on brass and steel. Unlike traditional Lathe and Milling Machines, the Die Sink EDM machine is an environmentally friendly thermal process that generates sparks to melt workpiece materials at high temperature. The removal of workpiece materials depends on the melting point of the electrodes. In addition, the Flow System was used to remove debris from the dielectric fluid and to act as an insulator to cool the workpiece. Overall, it is concluded that the materials with higher melting points took longer to process than materials with lower melting points. Moreover, electrode materials with high material removal rate (MRR) provided more Surface Roughness.
... The cost of the machine is the major cost of this process. (2) Electrical discharge coating is carried out on a well-established machine, the 'Electrical Discharge Machine', which is mostly used for drilling, machining complex shapes and hard materials, etc. [29,44]. Since this machine is available in most universities, further research on electrical discharge coating is possible, and it could lead to the standardization of the procedure. ...
... (5) Depth can be administered using the numerical controls available on an electrical discharge machine, whereas for other coating methods, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), etc., a special apparatus is required for control. For example, PVD coating needs a vacuum setup to control the machine surface [42,44]. ...
The electrical discharge machine (EDM) has been one of the most widely used non-traditional machines in recent decades, primarily used for machining hard materials into various complex shapes and different sizes and, nowadays, used for surface modifications/hard coatings. In this study, the SWOT (strengths, weaknesses, opportunities and threats) of electrical discharge coating was analyzed by conducting a case study. For the purpose of the case study, copper was deposited on the titanium alloy surface (Ti6Al4V). Three electrodes of different copper alloy materials, viz., brass,
bronze and copper, were selected for coating the Ti6Al4V surface. Input parameters such as current, pulse-on, pulse-off, flushing pressure and the electrode material were optimized to develop a uniform coating. Experiments were designed according to the L18 orthogonal array, and among them, the samples that showed proper coating, as seen with the naked eye, were selected for morphological and elemental analyses by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX. Further, the output responses, viz., the material deposition rate (MDR), electrode wear rate
(EWR), surface roughness (SR), elemental data (copper (Cu) and zinc (Zn)) and coating thickness (CT), were considered for the optimization of coatings. Implementing the Technique for Order Performance by Similarity to Ideal Solution, copper coating with a thickness of 20.43 µm, developed with an MDR with input parameters of 20 A current, 600 µs pulse-on, 120 µs pulse-off, 0.5 bar flushing pressure and the brass electrode, was selected as the optimum coating. The most influential parameters in this coating process were the current and pulse-on time. In this study, a SWOT table was developed to
depict the strengths, weaknesses, opportunities and threats of electrical discharge coating.
... Experimental results further revealed that maximizing the MRR while minimizing EWR and improving the surface roughness, cannot be achieved simultaneously at a particular combination of control parameters setting. Dwivedi & Choudhury [5] investigated the effect of tool rotation (0 & 1000 rpm) on AISI D3 steel during EDM. It shows that tool rotation significantly improves the MRR and surface finish by 41% & 12% respectively. ...
... GRA and TOPSIS have been chosen as optimization tools as these are capable of solving any complex and multi-criteria decision making problem in a very simple way by converting it into a single objective problem. Most of the studies on EDM are done for the tool rotation less than 1000 rpm in the literature [1,[3][4][5][6][7]. In this paper, we have used the higher tool rotation that is up to 1600 rpm starting with 900 rpm. ...
The present work investigates the optimization of process parameters of EDM for Al-2050 with different rotating tool electrodes (Cu, W & Cu-W alloy). Taguchi design of experiments linked with TOPSIS and GRA for prediction of optimizing output parameters has been developed. Five independent input parameters namely tool type, tool rotational speed, discharge current, pulse on time and pulse off time have been chosen as input variables to establish their influence on the output parameters such as MRR, TWR and Depth. Using MINITAB software, ANOVA has been determined to find the most significant parameters at a 95% confidence level. Estimated results are validated by the confirmatory test and it is found that improvement in the preference values are 0.880068 and 0.262154 using TOPSIS and GRA respectively with tool rotation. But the improvements in the preference values are 0.439190 and 0.115099 using TOPSIS and GRA respectively without tool rotation.
... They reported that the increase in the dielectric flow improved decontamination in the machining gap, flushing away gas bubbles and debris more rapidly, which improved the machining performance in the terms of material removal rate. Dwivedi et al. [41] improved machining performance of the EDM process using a rotating cylindrical electrode. They found that the rotating electrode increased the material removal rate by 41% and reduced surface roughness by 12% compared to using a stationary electrode. ...
The performance of electrical discharge machining for drilling holes decreases with machining depth because the conventional flushing and electrode cannot completely eliminate debris particles from the machining area. In this study, a modified electrode for self-flushing in the electrical discharge machining process with a step cylindrical shape was designed to improve machining performance for deep hole drilling. The experimental results of the step cylindrical electrode showed that the material removal rate increased by approximately 215.7%, 203.8%, and 130.4%, and the electrode wear ratio decreased by approximately 47.2%, 63.1%, and 37.3%, when compared with a conventional electrode for the diameters of 6, 9, and 12 mm, respectively. In addition, the gap clearance and concavity of the side wall of the drilled hole was reduced with the step cylindrical electrode. The limited high flank of the electrode led to an increase in the escape area of the debris that was partially removed from the machining area, and the limited secondary spark on the side wall of the electrode resulted in a reduction in machining time.
... The rotational motion of the tool electrode imparts a centrifugal force on the debris particles, which assists in the removal of debris particles [6]. It is a well-known fact that the imparted centrifugal force increases with an increase in the rotational speed of the tool electrode [29]. Due to this increased centrifugal force at higher rpm, the removal of debris particles from the IEG is faster in comparison with that at lower rpm [21,30], which enhances the stability of spark discharges and uniformity in spark distribution. ...
The performance enhancement of the rotary tool near-dry electrical discharge machining (RT-ND-EDM) process by modifying the tool electrode geometry was explored in the present work. The experiments were performed using the tubular tool, slotted tools, and helical tools. The number of slots in slotted tool electrodes and the number of starts in the helical tool electrodes were selected based on the experimental results. Also, the performance of the selected tool electrodes was compared with that of the basic tubular tool electrode. The effects of input parameters (tool rotation speed, current, pulse on time, gas pressure, and the LFR) on the performance of the RT-ND-EDM process are assessed for selected tool electrodes. This research established the efficacy of introducing slotted and helical features into rotating cylindrical tools to enhance the performance of the RT-ND-EDM process. The flushing of the inter-electrode gap is of decisive importance with respect to material removal rate, geometric accuracy, and surface quality of work material during the RT-ND-EDM process. The results revealed that a double-start helical-shaped tool electrode resulted in better process performance among all the selected shape electrodes.
... Rotation of tool electrodes during machining can improve the fluidity of dielectrics and the debris evacuation, so as to improve the performance of electrical discharge machining (EDM) [17]. Dwivedi et al. [16,18] found that the adoption of tool rotation can increase the material removal rate (MRR) by improving spark efficiency and effectively removing debris. The results show that the average MRR are improved by 41% and the tool wear rate (TWR) is increased by 13.5%. ...
Rotating electrodes can effectively improve the processing performance of micro-electrical discharge machining (micro-EDM), but there is still a lack of systematic research on the specific effects of electrode rotation and rotational speed changes. In this paper, the effects of electrode rotation and rotational speed on the discharge channel, debris stress, and debris motion in micro-EDM were analyzed theoretically. An AISI304 sheet was used as the workpiece and helical tungsten carbide alloy as the electrode. The through-hole drilling experiments of micro-EDM were carried out at low and high discharge energy and different electrode rotational speeds. In terms of processing efficiency, the effects of electrode rotation and rotational speed on material removal rate (MRR), relative tool wear ratio (RTWR), and short circuit number were analyzed. The results show that MRR increases first and then decreases, RTWR and short circuit number decrease first and then increase. In the aspect of processing precision, the impacts of electrode rotation and rotational speed on taper angle and overcut were analyzed. The results show that the electrode rotational speed has little effect on the change of the taper angle. In addition, when the electrode rotational speed is small, there is no obvious change in overcut. When the speed is too high, the overcut increases obviously and shows a trend of continuous increase. Finally, by comparing the experimental results, the optimal electrode rotational speeds of micro-EDM with two kinds of discharge energy were determined. The final experimental results also verify the correctness of the previous theoretical analysis.
... Another method is to use a rotating electrode to remove debris. Dwivedi and Choudhury [31] investigated both theoretically and experimentally the machining of high chromium and high carbon AISI D3 steel using rotating cylindrical electrodes. This technique resulted in a higher MRR because of the improved debris clearance and spark quality. ...
... An X-ray fluorescence system (model S8 Tiger from Bruker, Billerica, MA, USA) was utilized to identify the chemical compositions of the Ti6Al4V workpiece (see Table 1), and the physical properties of the workpiece material are shown in Table 2. During these tests, 30-mm-deep vertical blind holes with a 14 mm diameter were machined using the graphite electrodes as one of the most common electrode materials for Ti6Al4V [31]. The generic discharge conditions used for these tests are summarized in Table 3 as recommended by the EDM machine manufacturer for EDM drilling with graphite electrode and Ti6Al4V titanium alloy. ...
... (2) Figure 12 shows the resultant MRR for the eight different electrode geometries. In these EDM trials, as previously explained, a shaped electrode simultaneously rotates and retracts, which promotes self-pumping of the dielectric fluid [26,31]. This evacuates debris along the helical paths generated between the moving shaped electrode and the machined hole (see Figure 3b) and, thus, induces self-flushing of the debris through the gap at the top surface. ...
This article reports an experimental investigation of the efficacy of self-flushing in the Electrical Discharge Machining (EDM) process in terms of tool wear rate (TWR), hole taper angle and material removal rate (MRR). In addition to a plain cylindrical shape, electrodes of different cross sections (slotted cylindrical, sharp-cornered triangular, round-cornered triangular, sharp-cornered square, round-cornered square, sharp-cornered hexagonal and round-cornered hexagonal) were designed as a means of inducing debris egress and then fabricated in graphite. EDM drilling trials using the rotating shaped electrodes were carried out on a Ti6Al4V workpiece. The results revealed that, although a low TWR and minimum hole taper angle were achieved using a plain cylindrical electrode, the usage of rotating shaped electrodes provided self-flushing of the dielectric fluid during the EDM process, which led to an improvement in MRR compared to that achieved with a plain cylindrical electrode. Besides, in general, the electrodes with rounded corners are associated with a lower TWR, a lower hole taper angle and a higher MRR when compared to the electrodes with sharp corners. Considering these results, it was concluded that different process attributes, i.e., TWR, hole taper angle and MRR, are all greatly affected by the electrode shape, and thus, the proper selection of the electrode shape is a precondition to attain a specific response from the EDM process.
... The special rotary chuck has been fabricated for EDM deep hole process and mounted to the EDM machine. The tool rotation helps in improving the flushing ability and removal of debris from the machining gap during EDM of deep hole process [10]. During the EDM deep hole process the flow rate of dielectric flushing was set on a constant value. ...
In conventional flushing, when increasing the machining depth, the flushing ability becomes insufficient for ejection of the debris from machining gap. Debris concentration in the gap spark causes a process instability, low performance and high machining time etc. This paper proposes an innovative method of flushing technique for electrical discharge machining (EDM) of deep hole process. Tool electrode was specifically fabricated for flushing on the efficiency and stability of machining to promote the ejection of debris from machining gap. The performance of the deep hole process by electrical discharge machining under different flushing condition are presented. The results showed that the flushing through the tool electrode and multi-hole interior flushing are more preferred than side flushing. The result include 26.10% reduction in machining time (50 mm. in depth) when using multi-hole interior flushing electrode. In addition, the application of electrode multi-hole interior flushing electrode with electrode rotation improves the material removal rate (MRR) by 35.28% with 58.04% higher surface roughness (Ra).
... The need for microfeatures, components, and products is rapidly increasing in diverse industries such as electronics, medical and aviation [3]. Electrical Discharge Machining (EDM) is one of the most accurate nonconventional manufacturing processes used for cutting or creating intricate shapes in very hard or difficult-to-cut with electrically conducting materials [4][5][6]. EDM is a process of electric conductive material removal that filled with dielectric fluid between an electrode and a workpiece by using an accurately controlled electrical discharge (spark) through a small gap (approximately 10 to 50 microns) [7][8][9]. In EDM, the two electrodes that called electrode and workpiece are separated by the dielectric fluid [4,9]. ...
... EDM is a process of electric conductive material removal that filled with dielectric fluid between an electrode and a workpiece by using an accurately controlled electrical discharge (spark) through a small gap (approximately 10 to 50 microns) [7][8][9]. In EDM, the two electrodes that called electrode and workpiece are separated by the dielectric fluid [4,9]. The electrode and workpiece are connected to a DC power supply [10,11]. ...
Electrical Discharge Machining (EDM) is a non-conventional manufacturing process where the removal of the unwanted materials is performed without a direct contact between the electrode and workpiece. This paper reports the mathematical model of EDM pulses that focuses on open circuit and normal discharge of circuit condition. The model is based on the equivalent electrical model of voltage and current control where the normal discharge model employs ignition delay of 4µs, 10µs and 16µs. By applying Kirchhoff's voltage law, the voltage gap of an open circuit can be expressed according to a closed-loop network with zero current flow. As a result, the developed mathematical model capables to represent the pulse profile in EDM machining process.
