Electrical Discharge Machining Performance Research Articles

AI-based modelling and optimisation of rotating magnetic force assisted powder mixed EDM

Though widely used to process newly developed materials, electrical discharge machining (EDM) possesses poor machining efficiency. Modifications/hybridisation of EDM can improve its performance with respect to different quality parameters. Mixing powder in dielectric and applying magnetic field near machining zone are few of EDM modifications. The present paper investigates the performance of EDM with above mentioned modifications applied simultaneously. The innovative setup was designed and fabricated to perform rotary magnetic field assisted powder mixed EDM (MFPMEDM). The experiments were conducted on aluminium titanium di-boride metal matrix composite to evaluate MRR by varying different process parameters including powder concentration under the influence of magnetic field. The performance of both EDM and MFPMEDM has been compared and latter has been found much better in terms of process efficiency. Further, hybrid evolutionary optimisation algorithm has been used for modelling and optimisation of MRR.

Investigating the effect of cryogenic treatment of workpieces and tools on electrical discharge machining performance

<abstract> <p>In this competitive world, manufacturers must embrace new technology in order to differentiate their products and capture market leadership. This can be achieved using advanced materials; however, these materials are difficult to machine by using traditional machining processes. A very viable and practical unconventional machining process is electrical discharge machining (EDM). EDM processes need proper selection of input parameters to get optimum productivity aspects, namely, the material removal rate and tool wear rate. Thus, the present study aims at investigating the effect of cryogenically treated work pieces and tools, gap currents, gap voltages, pulse on time and pulse off time on the material removal rate and tool wear rate during EDM of Nitinol (NiTi) alloy, Monel (NiCu) alloy and beryllium copper (BeCu) alloy. The experimental results showed that cryogenic treatment significantly improved the electrical conductivity of the workpieces and tool electrodes, which resulted in an enhanced material removal rate and reduced tool wear rate.</p> </abstract>

Study of the performance of Cu-Gr composite tool during EDM of AISI 1020 mild steel

Copper and graphite are the commonly used tool materials in Electric Discharge Machining (EDM). The use of copper as tool material increases the material removal rate (MRR) of workpiece during EDM. However, the tool wear rate (TWR) of graphite electrode is less as compare to copper electrode. In the current work, an attempt has been made to find the performance of Cu-Gr composite material as EDM tool. Four EDM tools of different copper-graphite composition have been used to machine AISI 1020 mild steel. Both MRR and TWR have been considered to measure the performance of EDM. The results reveal that the increase of graphite percentage in Cu-Gr composite tool reduces TWR up to 83 % by reducing MRR 73%.

Optimization of EDM process parameters for TWR on machining of Inconel 600 superalloy using Taguchi approach

Electrical discharge machining (EDM) is a non-traditional machining technique that is commonly employed on hard materials. The fact that EDM can cut any conductivematerial, independently of its hardness, has made it popular. EDM is extensively used to shape or create advanced technological materials which are used in extreme conditions. The effects of input parameters on the effective machining of Inconel 600 superalloy was investigated in this study. The tool electrode was made of Tungsten Carbide (WC), and the dielectric fluid was EDM oil. The Taguchi method was used to investigate the effects of control factors including pulse-on-time (Ton), peak current (Ip), and gap voltage (Vg) on the performance criterion TWR. Using an orthogonal array (OA) L9, the research were carried out at three levels. The EDM performance aspects were investigated using the signal-to-noise ratio and ANOVA. The Taguchi technique was used to optimize the input and output parameters using the statistical software MINITAB-17. During the EDM process, TWR grows somewhat linearly with increasing Ip. TWR reduces as Vg increases, then increases as Vg increases. TWR increases with increasing Ton and then drops with increasing Ton. The tool wear rate is lowest at the first level of Ip, the second level of Vg, and the third level of Ton. ANOVA revealed that Ip, Vg, and Ton all had a significant influence on TWR. Obtained optimum input variables value for tool wear rate are Ip (30 A), Vg (94 V), and Ton (150 s). The predicted ideal range of TWR at 95% confidence level was confirmed by conducting confirmation experiments, wherein the TWR was achieved as 0.551 mm3/min. To validate Taguchi's optimization approach, confirmation tests were performed using optimal values of input parameters.

Investigation on the Wire Electric Discharge Machining Performance of artificially aged Al6061/B4C composites by Response Surface Method

Present research work is focused on investigation of material removal rate in Wire-ED Machining (EDM) of artificially aged Al-6061/ B4C reinforced composites with 2-6 wt.% in peak aged condition. Combined effect of B4C and artificial aging at 100°C improved the hardness by 20 - 170% under as cast and artificially aged condition. Initially the wire EDM experiments are conducted on Al6061 alloy and then the process parameters such as current, pulse-on time (ton) and pulse-off time (toff) are optimized to obtain the high material removal rate (MRR). At optimized conditions test samples with various % of B4C are machined to study their influence on MRR. The study revealed that current and toff had a significant influence. MRR increased as current is increased and it decreased as toff is increased. Maximum MRR at optimum settings, current : 5.53 A, Toff: 10 µs and Ton: 36.46 µs is 2.45 mg/min. Considering the limitation of the experimental set up the modified optimum settings (Toff: 10 µs, Ton: 30 µs and current : 5 A) resulted in average MRR of 2.39 mg/min with deviation of 0.20 mg/min. The study showed that there is no significant difference in MRR and the morphology of the machined surface with respect to test samples of different % of B4C particles as reinforcement in Al6061 composite.

The outcome of dielectric fluids in electrical discharge machining performance: A review

Electrical discharge Machining is a non-traditional machining process in which the material is removed by electrical discharge at short intervals in presence of a dielectric medium. The electrode is moved towards the gap until it becomes so small that the dielectric is ionized due to the immersion of voltage. EDM is mostly used in the die sinking industry to machine hard materials, however, it has lately been utilised to machine light materials like Ti alloy. Dielectric fluid plays an important role in the rate of material removal and the qualities of the machined surface in EDM. This study includes a review of the literature on the usage of dielectric fluid and its influence on the features of electrical discharge machining. Dielectric fluids have properties such as viscosity, good wetting capacity. examples of gaseous dielectric are oxygen, helium, argon. As dielectric fluid performs a very great function in any electrical discharge machining operation, the choice of dielectric medium is an essential consideration for EDM performance. Material removal rate and surface finish is essential response in EDM process and dielectric fluids has effective role of them. That is why dielectric is very important in the EDM process.

Experimental analysis of the influence of discharge gap on EDM performance

In order to reduce the machining time and improve the surface quality of holes, a high speed self adjusting electrical discharge machining (EDM) approach is needed with independent flushing system that were able to remove the debris in the machining process. With the change in the gap distance and depth of the hole drilled, the electrode automatically adjusts the gap with the help of a linear actuator. For that, the optimum gap distance for getting maximum result is crucial. Taguchi L27 orthogonal array technique is used for the preliminary experimental analysis. The study revealed that discharge gap which is proportional to the gap voltage is the most influential parameter that affects the surface finish and material removal rate. The formation mechanism of the hole in the copper plate had found out, in order to get the optimum gap distance for the maximum MRR, TWR, and ROC. The results from the comparison experiment shows that the best result will be get at 0.5 mm gap distance and this can be taken as the optimum gap distance for the automatic feeding mechanism. In addition, low voltage and current would benefit for the EDM process working in micro level and for the removal of the recast layer.

Effects of hybrid Al2O3- SiO2 nanoparticles in deionized water on the removal rate and surface roughness during electrical discharge machining of Ti-6Al-4V

Nowadays, special attention is paid to the application of nanoparticles to improve the performance of Electrical Discharge Machining (EDM). In this paper, modeling and optimizing the process parameters of Nanopowder Mixed Electrical Discharge Machining (NPMEDM) is studied. In this study, the effect of aluminum oxide (Al2O3) and silicon oxide (SiO2) nanoparticles on the deionized water dielectric is investigated simultaneously in the process of electrical discharge machining of Ti-6Al-4V alloy. After analyzing the parameters, the discharge current, concentration, pulse on time, and relative composition are considered as input factors. Response Surface Methodology (RSM) using Design-Expert software is employed for the design of the experiments, analysis of the results, and optimization of the parameters. The results show that the best surface morphology is obtained by machining with the addition of nanoparticles in the relative composition of 50%. In this percentage of the composition, the surface of the workpiece has the least value of crack and recast layer. In addition, the maximum value of the material removal rate (MRR) and minimum value of tool wear rate (TWR) can be achieved in the discharge current of 12 A, pulse on-time of 100 μs, and relative composition of 75% Al2O3 – 25% SiO2.

Development and Investigation of an Inexpensive Low Frequency Vibration Platform for Enhancing the Performance of Electrical Discharge Machining Process.

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.

Novel carbon nanotubes reinforced copper composite electrode for improved performance of electric discharge machining

Composite electrode fabrication is an effective strategy to improve the performance of the Electric Discharge Machining (EDM) process. In this work, a new copper/carbon nanotube (Cu/CNT) metal matrix composite electrode at a different volume fraction of CNT (0.35%, 0.70% and 1.05%) is developed using a spark plasma sintering (SPS) method. The real-time functional performance of the developed electrode on the EDM machining is also examined by changing the EDM process parameters (discharge current, pulse-on time and voltage). The composite electrode characterization results indicated that as the percentage of CNT increases from 0.35 to 1.05 vol%, the density reduced and electrical resistivity increased due to the rise in porosity. Performance review of CNT-infused electrodes during EDM machining revealed a higher Material removal rate (MRR) and good surface finish than the Cu electrodes due to high discharge energy and enlargement in the spark gap. However, Cu/CNT electrodes wore out faster than Cu electrodes by 90%, possibly due to the reduction in thermal conductivity induced by porosity effects. Comprehensively, although the addition of CNT affected the mechanical attributes of the electrode, it offered significantly better output (MRR and Surface finish) than the Cu electrode with limitations on electrode wear.

A morphological and textural analysis of Inconel-718 aerospace alloy processed through electrical discharging machining

The Inconel 718 has captured global attention for its huge applications in the aerospace and defense field. However, a limited approach is noticed to investigate this material's responses and morphological features after electrical discharge machining operation. This study wants to offer a more detailed investigating approach, including the analysis of morphological features, recast layer, microhardness, elemental composition, and several textural defects and basic responses. Scanning electron microscopy is used to investigate several textural features, defects, cracks, and recast layers. The findings claim 538 nm–2.168 µm and 14–41 µm variations in crack width and recast thickness, respectively, which increase with pulse current and pulse on-time. However, the low discharge energy can provide better micro-hardness than higher discharge conditions due to having sufficient time for flushing and heat dissipations. The recast surface and the interfaces are, respectively, 7.58%–13.16% and 22.75%–32.74% harder with low discharge condition than the intermediate and higher discharge condition. Moreover, the Energy Dispersive X-ray analysis reported the emigration of 17.81% of carbon and 0.33% of copper from the dielectric and tool during the machining.

Investigation into the Electrical Discharge Machining Parameters of DIN 2767 Tool Steel Using Taguchi Method

Electrical discharge machining (EDM) is one of the most crucial non-traditional machining methods used in molds and dies manufacturing, and conductive materials machining, which are difficult to machine by traditional methods. The EDM performance is affected by several machining parameters with different contribution percentages. In this study, the experimental investigations were conducted on DIN 2767 tool steel using CuCrZr, Cu and CuCo1Ni1Be (CNB) electrodes. The most influential process parameters were focused on to improve the EDM performance. The value of the process parameters and their levels were discharge current (6, 12 and 25 A), pulse-on time (50, 200 and 800 μs) and pulse-off time (50, 200 and 800 μs). Optimal levels of machining process parameters were obtained by employing the Taguchi L27 orthogonal arrays. The experimental results showed that the optimal combination of the machining parameters for maximum material removal rate was A3B2C1 using a CNB electrode. For minimum tool wear rate, the optimal parametric combination was A1B3C1 and Cu electrode. The optimal parametric combination was A1B3C3 and CuCrZr electrode for minimum surface roughness. The study further revealed the relation and interaction effect between process parameters for the performance measures. Lastly, the process parameters affected and changed the DIN 2767 tool steel workpieces’ surface integrity as evidenced by the scanning electron microscopy images.

Performance evaluation of graphite and titanium oxide powder mixed dielectric for electric discharge machining of Ti\u20136Al\u20134V

Ti–6Al–4V is the most commonly used titanium alloy in aerospace, marine, and biomedical applications. Due to the properties of poor machinability in conventional machining, Electrical Discharge Machining (EDM) is considered a prospective alternative for machining this strategic material. This study aims at enhancing the performance of powder mixed EDM (PMEDM) in the machining of Ti–6Al–4V with the application of two different types of powders, namely Graphite (Gr) and Titanium Oxide (TiO2) powders, with different concentrations in dielectric—kerosene. The effect of these powers and their relative quantities are studied in terms of metal removal rate (MRR), tool wear rate, Surface Roughness, and surface integrity. Machining is performed using the copper electrode and kerosene as the dielectric medium. A separate container and a submersible pump are used to limit the quantity of powder and keep the powder in suspension, respectively. Design of experiments guided by Design-Expert software is employed to minimize the number of experimental runs and develop empirical models of response parameters in terms of the variable parameters—peak current, powder type, and powder concentration. Findings indicate that TiO2 powder has a much higher effect on MRR compared to graphite powder, as the maximum MRR in the case of TiO2 powder is recorded 41.01 mm3/min against 11.98 mm3/min for graphite powder, i.e., 3.42 times higher. Similarly, the tool wear ratio for TiO2 powder is 0.0704 against 0.1219 for graphite powder at the maximum MRR, which is 1.73 times lower compared to that of graphite powder. The same ratios at the minimum MRR for TiO2 is 0.0098, and for graphite power is 0.0282, which is again 2.88 times lower compared to that of graphite powder. In terms of average surface roughness, Ra, the performance of TiO2 is far better compared to graphite powder since the maximum surface roughness attained with TiO2 powder is 3.265 μm against 9.936 μm for graphite powder at the highest MRR and the same attained at the lowest MRR are 2.228 μm and 2.411 μm for TiO2 and graphite powders respectively. The mechanism of the effects of PMEDM on surface texture has also been observed using SEM images to study the influence of powder concentration on surface morphology.

Effect of Conductive, Semi-conductive and Non-conductive Powder-Mixed Media on Micro Electric Discharge Machining Performance of Ti-6Al-4V

Effect of Conductive, Semi-conductive and Non-conductive Powder-Mixed Media on Micro Electric Discharge Machining Performance of Ti-6Al-4V

Improving Machining Performance for Deep Hole Drilling in the Electrical Discharge Machining Process Using a Step Cylindrical 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.

Investigation on hole diameter non-uniformity of hole arrays by ultrasonic vibration-assisted EDM

Ultrasonic vibration-assisted electrical discharge machining (EDM) as an alternative advanced processing technology has been widely used to machine micro-hole arrays. However, there exists a concentration of debris particles in the discharge gap, which affects the machining accuracy of micro-hole arrays by ultrasonic vibration-assisted EDM with tool electrode arrays. In this study, a series of experiments of ultrasonic vibration-assisted EDM of micro-hole arrays with tool electrode arrays were performed, and the experimental results demonstrate that the hole diameter in the central holes of hole arrays is a little bigger than those in the peripheral holes of hole arrays. To illustrate the mechanism of hole diameter non-uniformity of micro-hole arrays by ultrasonic vibration-assisted EDM with tool electrode arrays, a three-dimensional gap flow field model for ultrasonic vibration-assisted EDM of micro-hole arrays was proposed based on computational fluid mechanics. In the flow field model, the laws of flow field velocity and debris particles distribution were simulated numerically under the effect of ultrasonic vibration. To investigate the rules of flow field velocity and debris particles distribution during ultrasonic vibration-assisted EDM of micro-hole arrays, the flow field model of 3 × 3 micro-hole arrays, 5 × 5 micro-hole arrays, and 10 × 10 micro-hole arrays were considered. The numerical simulation results show that in the flow field, the concentration degree of debris particles in the peripheral holes of micro-hole arrays is lower than those of the central holes of micro-hole arrays. The non-uniformity distribution of debris particles of the central holes and the peripheral holes of micro-hole arrays strength the local electric field and leads to non-uniformity of discharge breakdown probability, which causes the hole diameter non-uniformity of micro-hole arrays by ultrasonic vibration-assisted EDM. The experimental and numerical simulation results reveal the mechanism of hole diameter non-uniformity of micro-hole arrays by ultrasonic vibration-assisted EDM with tool electrode arrays and suggest that decreasing the concentration of debris particles is the effective way to improve the performance of EDM of micro-hole arrays.

Experimental investigation for sustainable electric discharge machining with Pongamia and Jatropha as dielectric medium

ABSTRACT This research work is a feasibility analysis for the newly developed dielectric based on non-edible vegetable oil, Pongamia (Pongamia pinnata) and Jatropha (Jatropha curcas) for electrical discharge machining (EDM). The traditional EDM uses kerosene as a dielectric with poor safety and unfriendly environmental consequences. In addition to eliminating the risks from kerosene to operator and atmosphere, bio-dielectric can also enhance the machining performance of traditional sinking EDM. As input parameters peak current, gap voltage, and pulse on time were selected and one variable at a time (OVAT) strategy was used to design experimental plans to investigate the application of the newly proposed bio-dielectric. In addition, the mechanism of material removal with Pongamia and Jatropha bio-dielectric is also discussed in detail. The results obtained have shown that the performance of the proposed Pongamia and Jatropha is better than commercially available kerosene oil for MRR, lower EWR and SR, and machined specimens with better surface integrity. It is proposed that dielectric based on Pongamia and Jatropha oil may be used as a hydrocarbon-based dielectric alternative to improve the sustainability of the EDM process.

Enhancement of material removal rate in Electric Discharge Machining of Inconel 718 using cryo-treated graphite electrodes

Recent advancements witnessed the growth of many Nickel based super alloys like Inconel 718 which has very high strength and corrosion resistance. However, non-conventional machining processes are required for these super alloys due to its poor machinability. Electric Discharge Machining (EDM) is one such non-conventional machining operation where we can machine the materials irrespective of their hardness & strength. One of the limitations of EDM is the low Material Removal Rate (MRR). This paper discusses the effects of cryogenically (cryo) treated graphite electrodes on the MRR of Inconel 718 during EDM operation. Experimental results showed that MRR is improved by using the cryo-treated graphite electrodes.

Comparative study of parametric effects on the performance of simple and powder mixed EDM using aluminium and graphite powder on Inconel X750 alloy

In the present scenario, Electrical Discharge Machining (EDM) is one of the most entrenched non-conventional machining processes which are widely used in different manufacturing sectors worldwide. Generally, the conductive materials, which having geometrically complex shape and extremely difficult to machine by conventional machining processes are machined by EDM. The further improvement of the machining efficiency of this EDM process may be enhanced by using powder suspended dielectric fluid which is called Powder Mixed EDM (PMEDM) process. In this research work, an attempt has been made to analyze the comparative study of parametric effects on the performance characteristics like material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) in terms of average value of roughness parameter (Ra) of simple (without powder) and powder mixed EDM using Aluminium (Al) and Graphite powder on Inconel X750 alloy by experimental investigation. Here, in our study, Peak current (Ip) pulse on time (Ton) and pulse off time (Toff) have been taken as the variable process parameters and concentration of powder (Cp) is taken as 6 g/l in all cases throughout the experimentation. From the experimental results, it has been observed that PMEDM gives lower MRR but better surface finish in comparison with conventional EDM technique (without powder). Also, it has been noticed that graphite powder mixed EDM is more effective for getting better surface finish of Inconel X750 alloy compared to Al mixed PMEDM process.

EDM performance characteristics and electrochemical corrosion analysis of Co-Cr alloy and duplex stainless steel: A comparative study

Cobalt-chromium alloy (F-90) and duplex stainless steel (DSS-2205) belong to the family of metallic biomaterials, which are frequently used for the manufacture of dental prosthetics, artificial implants including knee and hip joints. This article addresses the investigation highlights of electrical discharge machining (EDM) of Co-Cr alloy and duplex stainless steel using different electrode materials for the evaluation of optimum machining parameters. The samples with superior machining performance and surface integrity were analyzed by electrochemical corrosion testing and found that the EDM treated samples portrayed a notable improvement in the corrosion resistance compared to bare metal. Our results demonstrated that both the substrates i.e. Co-Cr alloy and DSS-2205 were dominantly affected by the intensity of the applied current, and participated in the material removal rate with a contribution of 93.81% (23.37 mm3/min., Co-Cr alloy) and 87.32% (39.76 mm3/min., DSS-2205) respectively. However, the surface roughness of the machined Co-Cr alloy (1.080 µm) was majorly influenced by the current (contribution: 67.24%) and electrode (contribution: 28.27%). Whereas, pulse-on (contribution: 58.37%) and electrode (contribution: 30.52%) were significant for the surface roughness (1.150 µm) of the machined DSS-2205. Moreover, the machined surface also demonstrates the porosity (∼3 to ∼5 µm) and formation of intermetallic oxides, carbon phases on the samples machined at a higher value of current i.e. 16 Ampere. Field emission scanning electron microscopy and X-ray diffractometer were used to scrutinize the surface topography and compositional analysis of the machined substrates. The alternation of the substrate surface observed helpful in enhancing the corrosion resistance of Co-Cr alloy and duplex stainless steel by 80.88% (corrosion rate: 0.00029 mm/year) and 96% (corrosion rate: 0.00763 mm/year), comparative to their respective untreated samples.