Electrical Discharge Machining Experiments Research Articles

Bi-objective optimization of an EDM process with Cu-MWCNT composite tool using single-valued neutrosophic grey relational analysis

Purpose In many of today’s manufacturing industries, such as automobile, aerospace, defence, die and mould making, medical and electrical discharge machining (EDM) has emerged as an effective material removal process. In this process, a series of discontinuous electric discharges is used for removing material from the workpiece in the form of craters generating a replica of the tool into the workpiece in a dielectric environment. Appropriate selection of the tool electrode material and combination of input parameters is an important requirement for performance enhancement of an EDM process. This paper aims to optimize an EDM process using single-valued neutrosophic grey relational analysis using Cu-multi-walled carbon nanotube (Cu-MWCNT) composite tool electrode. Design/methodology/approach This paper proposes the application of grey relational analysis (GRA) in a single-valued neutrosophic fuzzy environment to identify the optimal parametric intermix of an EDM process while considering Cu-MWCNT composite as the tool electrode material. Based on Taguchi’s L9 orthogonal array, nine experiments are conducted at varying combinations of four EDM parameters, i.e. pulse-on time, duty factor, discharge current and gap voltage, with subsequent measurement of two responses, i.e. material removal rate (MRR) and tool wear rate (TWR). The electrodeposition process is used to fabricate the Cu-MWCNT composite tool. Findings It is noticed that both the responses would be simultaneously optimized at higher levels of pulse-on time (38 µs) and duty factor (8), moderate level of discharge current (5 A) and lower level of gap voltage (30 V). During bi-objective optimization (maximization of MRR and minimization of TWR) of the said EDM process, the achieved values of MRR and TWR are 243.74 mm3/min and 0.001034 g/min, respectively. Originality/value Keeping in mind the type of response under consideration, their measured values for each of the EDM experiments are expressed in terms of linguistic variables which are subsequently converted into single-valued neutrosophic numbers. Integration of GRA with single-valued neutrosophic sets would help in optimizing the said EDM process with the Cu-MWCNT composite tool while simultaneously considering truth-membership, indeterminacy membership and falsity-membership degrees in a human-centric uncertain decision-making environment.

Optimization of process parameters and performance for machining Inconel 718 in renewable dielectrics

In this study, the optimization of processing parameters of Inconel 718 using electrical discharge machining (EDM) with three kinds of renewable dielectrics (soybean oil, sunflower seed oil, and rapeseed oil) was studied. As input process parameters, pulse current, pulse duration, duty ratio, and dielectric type were all utilized. The machining performance indices of EDM were material removal rate (MRR), surface roughness (Ra), energy pulse ratio per volume (EEV), and exhaust emission characteristics (EEC). The response surface method (RSM) was used to carry out the central composite design of the EDM experiment, and it looked into how process parameters affected machining performance. In addition, the extreme learning machine (ELM)-improved integrated beta-distribution cuckoo search (IBCS) algorithm was used to optimize the EDM process, and the optimization results were verified by experiments. The research results demonstrate that the predicted results are generally better than the experimental results, and the maximum and average deviations of the experimental results are within the acceptable range (maximum deviation <20%, average deviation <15%). The effectiveness of the optimization algorithm was proved, which was helpful in improving the performance of EDM, reducing energy consumption and emissions, and improving the sustainability of EDM.

Experimental Study on EDM SKD61 with Different Material Electrodes

The electrode is an essential tool in electrical discharge machining (EDM). The quality and efficiency of EDM are directly determined by the performance of electrode materials. Copper tungsten alloy (CuW50) and pure copper cuboid electrodes were fabricated by wire-cut electrical discharge machining (WEDM). The machining parameters of processing current, pulse width and machining efficiency were selected as test variables, and the single-factor EDM experiment was carried out on SKD61 die steel with the goal of processing speed v and machined surface Ra. The results show that the processing speed and machined surface obtained by using pure copper electrodes are better than those obtained by using the CuW50 electrode. The processing current, pulse width and machining efficiency parameters corresponding to the maximum processing speed and the optimal machined surface obtained using the two material electrodes are basically different.

Relationship between energy consumption and surface integrity aspects in electrical discharge machining of hot work die steel

The present work deals with the relationship between energy consumption and surface integrity aspects in electrical discharge machining (EDM) of hot work die steel. Initially, the non-conventional machining experiments were performed with 1.2344 hot work die steel material and the surface integrity aspects such as surface topography, power spectral density analysis, surface roughness etc. were measured with high end instruments. Then, the energy consumption data during machining was analyzed with Labview software. Finally, the relationship between two technological contributors were established and the results were compared with different process parameters. The results demonstrated that there is a direct relationship between the energy and surface integrity aspects while performing EDM experiments. The lowest Sa and Sz values were reached for the highest tested pulse voltage values (U = 200 V) and were respectively lower by 34% and 44% than ones reached during EDM with the lowest pulse voltage U = 80 V.

Performance analysis of electrode materials in electro discharge machining of monel K-500

The present work focusses on the electrical discharge machining (EDM) of Monel K 500 super alloy with different electrodes. The study’s objective is to examine the effects of process parameters and electrode materials (Cu, W-Cu, and graphite) in terms of surface quality, material removal rateand electrode wear. In this context, EDM experiments have been designed and performed using the L27 standard orthogonal array of the Taguchi method with a statistical approach. The outcomes of this study reveal that the current plays an important role to improve the EDM machining performance of Monel K 500. The surface quality is approximately 11.62% and 55.52%, respectively better when Monel K-500 alloy is machined with copper electrodes compared to those in W-Cu and graphite electrodes. Moreover, The W-Cu electrode’s wear is approximately 15.73% and 21.05%, respectively less than those of graphite and Cu electrodes in optimum processing conditions. Graphite electrodes are better than Cu and W-Cu electrodes in terms of material removal rate. The statistical results also show that the estimation equations developed to select the optimum production conditions to give high accuracy results.

Evaluation of the Performance of Atomic Diffusion Additive Manufacturing Electrodes in Electrical Discharge Machining

Atomic Diffusion Additive Manufacturing (ADAM) is an innovative Additive Manufacturing process that allows the manufacture of complex parts in metallic material, such as copper among others, which provides new opportunities in Rapid Tooling. This work presents the development of a copper electrode manufactured with ADAM technology for Electrical Discharge Machining (EDM) and its performance compared to a conventional electrolytic copper. Density, electrical conductivity and energy-dispersive X-ray spectroscopy were performed for an initial analysis of both ADAM and electrolytic electrodes. Previously designed EDM experiments and optimizations using genetic algorithms were carried out to establish a comparative framework for both electrodes. Subsequently, the final EDM tests were carried out to evaluate the electrode wear rate, the roughness of the workpiece and the rate of material removal for both electrodes. The EDM results show that ADAM technology enables the manufacturing of functional EDM electrodes with similar material removal rates and rough workpiece finishes to conventional electrodes, but with greater electrode wear, mainly due to internal porosity, voids and other defects observed with field emission scanning electron microscopy.

Direct Observation of Discharge Phenomena in Vibration-Assisted Micro EDM of Array Structures.

The batch mode electrical discharge machining (EDM) method has been developed to improve the throughput and accuracy in fabricating array structures, but the process suffers from insufficient debris removal caused by the complex electrode geometry. Tool vibration has been used to improve flushing conditions, but to date the underlying mechanism of the tool vibration on the micro EDM of array structures remains unclear. This study aimed to investigate the effect of tool vibration on the machining process by direct observation of the discharge phenomena in the discharge gap by using a high-speed camera. Micro EDM experiments using 9 and 25 array electrodes were performed, and the effect of tool vibration on the discharge uniformity and tool wear was evaluated. It was found that tool vibration improved the uniformity of the discharge distribution, increased the machining efficiency, and suppressed the tool wear. The discharges occurred in periodic intervals, and the intensity increased with the amplitude of tool vibration. The results of this study indicate that the vibration parameters determine the discharge period duration and intensity to achieve optimum stability and efficiency of the machining process.

The Existence of Autonomous Chaos in EDM Process

The dynamical evolution of electrical discharge machining (EDM) has drawn immense research interest. Previous research on mechanism analysis has discussed the deterministic nonlinearity of gap states at pulse-on discharging duration, while describing the pulse-off deionization process separately as a stochastic evolutionary process. In this case, the precise model describing a complete machining process, as well as the optimum performance parameters of EDM, can hardly be determined. The main purpose of this paper is to clarify whether the EDM system can maintain consistency in dynamic characteristics within a discharge interval. A nonlinear self-maintained equivalent model is first established, and two threshold conditions are obtained by the Shilnikov theory. The theoretical results prove that the EDM system could lead to chaos without external excitation. The time series of the deionization process recorded in the EDM experiments are then analyzed to further validate this theoretical conclusion. Qualitative chaotic analyses verify that the autonomous EDM process has chaotic characteristics. Quantitative methods are used to estimate the chaotic feature of the autonomous EDM process. By comparing the quantitative results of the autonomous EDM process with the non-autonomous EDM process, a deduction is further made that the EDM system will evolve towards steady chaos under an autonomous state.

Investigation on the geometric evolution of microstructures in EDM with a composite laminated electrode

Based on the difference in the wear rate of different materials in electrical discharge machining (EDM), wear-variation EDM (WV-EDM) takes full advantage of the electrode wear, which has always been considered as a headache in past research work, to continuously mass fabricate surface microstructures. However, the mechanism of the electrode wear in WV-EDM is not clear, which means that the optimization of the processing parameters and the law of the electrode wear are based on large numbers of experiments, resulting in a lot of waste of experimental materials, equipment, and human resources. In order to achieve green, healthy production and save resources, it is urgent to minimize the amount of EDM experiments on the premises of ensuring research quality and production demand. In view of the variety of electrode materials, this paper studies differences in material removal by single-pulse EDM and proposes a discharge erosion strategy of EDM with composite laminated electrodes (CLEs). After that, a two-dimensional simulation model was established to investigate and predict the geometric evolution of the electrode and workpiece during EDM. Finally, the accuracy of the model was evaluated by comparing profiles derived from simulations and experiments. The statistically relative error of the simulation model was less than 5%, indicating that the simulation model could provide theoretical guidance for the sustainable mass production of surface microstructures by WV-EDM, thereby greatly reducing the number of experiments, saving resources, and improving the experimental efficiency.

Experimental investigation on electrical discharge machining of steel H13

Abstract Electrical Discharge Machining (EDM) is being used to machine components made out of hard alloys and are geometrically complex in shapes. Different types of materials like tool steels, composites, carbides and super alloys are difficult to machine by conventional machining process can be machined by EDM. But this process still has some limitations during machining of hard alloys like tool steel (H13). This material finds application in various types of industries such as tool and die, nuclear and aerospace etc. In this research paper, simultaneous optimization of output parameters over cut and material removal rate is done using desirability approach. Orthogonal array (L18) design was used to perform the EDM experiment on H 13 steel.

Influence of Electrode Material and EDM Parameters on Electrode Wear of AISI H13 Steel

Abstract: Electrical discharge machining (EDM) is a non-traditional process that uses the electrical spark discharge to machine electrically conducting materials for geometrically complex shapes or hard materials. In the current work, cupper and brass were used as the electrode material, and AISI H13 steel as the workpiece. Different input parameters were investigated namely: 20, 30, 40 A current, 50, 100, 150 μs pulse on time, and 1, 3, 6 mm gap. The workpiece thickness was fixed to 4 mm and the pulse off time was 25 μs. All EDM experiments were carried out in diesel oil and the voltage was 140 V. The results showed that the electrode wear decreased with increasing the pulse on time and gap and increased with increasing current for copper and brass electrode. The optimal conditions for minimum tool wear were: pulse on time 150 μs, current 20 A, and gap 6 mm for copper and brass electrodes. Electrode wear is minimum for copper at all parameter values compared to brass electrode.

The effect of alumina powder in dielectric on electrical discharge machining parameters of aluminum composite A413-Al2O3 by the Taguchi method, the signal-to-noise analysis and the total normalized quality loss

The machining capability of metal composites is different compared to other materials because of their specific physical and mechanical properties. The aluminum composite A413 reinforced with Alumina powder is one of the materials which causes rapid erosion of the tool if traditional machining methods are employed. In this research, the electrical discharge machining experiments were conducted using the Taguchi method. After analysis of variance (ANOVA) using simultaneous analysis of total normalized quality loss (TNQL), and signal-to-noise ratio (S/N) of outputs, the effect of each parameter such as current intensity, voltage, pulse on-time and pulse off-time have been investigated. These parameters are influential on material removal rates, surface roughness, and tool wear ratio of electric discharge machining in two cases of with alumina powder and without alumina powder in dielectric. The outcomes of this research indicate that the use of Alumina powder 3 g/L in kerosene dielectric averagely reduces the material removal rate by 7.8%, increases the surface roughness by 8.8%, and decreases the tool wear ratio by 1.3%. Also, the results of analysis of total normalized quality loss and signal-to-noise ratio of the experiment have been shown as the first level of voltage (A1), the first level of current intensity (B1), the first level of pulse on time (C1), and the third level of pulse off time (D3).

Stirring tank design for powder-mixed EDM SiC/Al and solid-liquid suspension uniformity research

In order to solve the problem of non-uniform powder concentration in electrical discharge machining (EDM) working fluid, a mathematical model of powder particle movement in stirred tank was established, and the flow field and solid-liquid suspension uniformity were simulated in this paper. The factors of slot shape, depth-diameter ratio, blade angle, blade installation height, and solid particle volume fraction which affected flow field distribution, solid suspension particle uniformity, and power consumption were researched, and the stirred tank structure was optimized. When the ratio of spherical stirred tank depth to diameter is 0.8, the blade design angle is 45°, and the installation height of impeller blade is 120 mm, the suspension uniformity of solid particles is the best and the power consumption is the smallest. Under the conditions of Al powder concentration 4 g/L, pulse width 175 μs, and pulse interval 75 μs, the powder-mixed EDM experiment of SiC/Al functionally gradient material was carried out with this optimized stirring device. The results show that the material removal rate of powder-mixed EDM increased by 24.82% and the surface roughness decreased by 27.28% than that of the conventional EDM.

Electrical discharge machinable (Y, Nd) co-stabilized zirconia – Niobium carbide ceramics

Electrical discharge machining (EDM) of electrically conductive ceramics offers the possibility to manufacture customized ceramic components from sintered blanks. In this study two different yttria neodymia co-stabilized TZP materials containing 28 vol% niobium carbide were manufactured by hot pressing at 1275 °C–1400 °C and axial pressure of 60 MPa and compared to a 3Y-TZP based reference. The co-stabilized ceramics offer a strength up to 1250 MPa and a hardness of 14 GPa. The fracture resistance can be tailored between 7.4–9.7 MPa√m by variation of the yttria/neodymia ratio and the sintering temperature. These composites, however, require an exact setup of machining parameters. Die sinking EDM experiments revealed that the dominant material removal mechanism is melting. Machined surfaces can achieve low roughness Ra =0.3 μm combined with material removal rates of 1.5 mm³/min. The choice of excessively high energy parameters in EDM may lead to crack formation, spallation and phase accumulation during re-solidification.

Research on the combined electrochemical machining and electrical discharge machining technology for closed integer impeller

In order to improve the machining efficiency of engine closed integral impeller, the electrochemical machining (ECM) and electrical discharge machining (EDM) combined technology was proposed. ECM was used to remove the large machining allowance with high efficiency, and then the precision processing was accomplished by EDM. Because the two ends of the vortex channel are large and the middle is narrow, so the special-shaped vortex channel was divided into internal and external flow channels. First of all, based on the problem of flow field diverge and non-uniform in ECM S-03 special stainless steel material, the method of reverse flow ECM external flow channel was proposed. The ECM fixture design of internal and external flow channels was carried out, and the composite electrolyte composition of 5%NaCl+16%NaNO3+4%NaClO3 was obtained. Secondly, the EDM rough and precision machining electrodes were designed and the EDM experiment has done. Finally, the combined ECM and EDM experiment was finished. The experiment result showed that the combined method is feasible for machining closed integral impeller; the machining efficiency is 30% higher than that of EDM alone.

Assessment Of Surface Integrity During Electrical Discharge Machining Of Titanium Grade 5 Alloys (Ti-6Al-4V)

Abstract Machining induced surface integrity is studied in the context of Electrical Discharge Machining (EDM) of Grade 5 Ti-alloy (Ti-6Al-4V). Experiments are conducted using copper electrode submerged in kerosene (as dielectric media). Different settings of peak discharge current, and pulse-on duration are utilized for conducting EDM experiments. Surface integrity of the EDMed specimen is assessed in purview of surface morphology, and topographical characteristics like surface roughness, surface crack density, white layer thickness, metallographic features, material migration, and micro-indentation hardness. Effects of peak current, and pulse-on duration are observed on influencing surface integrity of the end product. Additionally, data in regards of material removal efficiency, and tool wear rate are presented to support root causes behind surface and sub-surface damages.

Energy distribution in cool electrode of electrical discharge machining based on wave-particle dualism

This paper studies the energy distribution in cool electrode of electrical discharge machining (EDM) on the basis of the wave-particle duality of matter. First, the movement of electrons and ions in the discharge channel was investigated in this article through the wavelength calculation of particles in a discharge channel. The main characteristic of electrons is wave and the moving form is prioritized for diffraction. Ions are mainly characterized by particles. These ions continuously vibrate in the mean free path. Second, a numerical calculation model is proposed on the basis of particle movement. The temperature field in the discharge channel of the cool electrode in the EDM to the titanium alloy is examined using the ANSYS software and simulation result is validated experimentally. Experimental results show that the diameter of the electric corrosion pit on the cool electrode surface is 355 μm, which is less than the electric corrosion pit diameter of 470 μm on a conventional electrode surface. Eventually, the EDM experiment was carried out under the same processing conditions with the cool electrode and the conventional electrode, respectively. The result shows that using cool electrodes in EDM can reduce electrode wear and increase machining efficiency.

Intelligent approach for process modelling and optimization on electrical discharge machining of polycrystalline diamond

Polycrystalline diamond (PCD) is increasingly becomes an important material used in the industry for cutting tools of difficult-to-machine materials due to its excellent characteristics such as hardness, toughness and wear resistance. However, its applications are restricted because of the PCD material is difficult to machine. Therefore, electrical discharge machining (EDM) is an ideal method suitable for PCD materials due to its non-contact process nature. The performance of EDM, however, is significantly influenced by its process parameters and type of electrode. In this study, soft computing technique was utilized to optimize the performance of the EDM in roughing condition for eroding PCD with copper tungsten or copper nickel electrode. Central composite design with five levels of three machining parameters viz. peak current, pulse interval and pulse duration has been used to design the experimental matrix. The EDM experiment was conducted based on the design experimental matrix. Subsequently, the effectiveness of EDM on shaping PCD with copper tungsten and copper nickel was evaluated in terms of material removal rate (MRR) and electrode wear rate (EWR). It was found that copper tungsten electrode gave lower EWR, in comparison with the copper nickel electrode. The predictive model of radial basis function neural network (RBFNN) was developed to predict the MRR and EWR of the EDM process. The prominent predictive ability of RBFNN was confirmed as the prediction errors in terms of mean-squared error were found within the range of 6.47E−05 to 7.29E−06. Response surface plot was drawn to study the influences of machining parameters of EDM for shaping PCD with copper tungsten and copper nickel. Subsequently, moth search algorithm (MSA) was used to determine the optimal machining parameters, such that the MRR was maximized and EWR was minimized. Based on the obtained optimal parameters, confirmation test with the absolute error within the range of 1.41E−06 to 5.10E−05 validated the optimization capability of MSA.

Comparative study of expert predictive models based on adaptive neuro fuzzy inference system, nonlinear autoregressive exogenous and Hammerstein–Wiener approaches for electrical discharge machining performance: Material removal rate and surface roughness

In this study, material removal rate (MRR) and surface roughness (Ra) in electrical discharge machining process have been modeled to make the process more efficient and reliable. First, adaptive neuro fuzzy inference system as one of the most used methods has been applied for prediction of material removal rate and Ra. Also a proposed method, that is, nonlinear modeling by system identification, has been applied to predict material removal rate and Ra. A group of electrical discharge machining experiments considering four input variables was conducted to collect dataset for training the predictive models. At the end, the comparison of predicted results from both approaches with experimental data shows that the new method has a much better performance than the adaptive neuro fuzzy inference system approach.

Study on the Effect of External Hydrostatic Pressure on Electrical Discharge Machining

This paper describes the influence of external hydrostatic pressure on material removal rate of electrical discharge machining (EDM). In EDM, because electrode materials and dielectric liquid are evaporated by arc plasma, gas bubbles are generated in the working gap. The machining gap is mostly occupied with gas bubbles during the machining process. In this study, machining was conducted under some external hydrostatic pressure from below to above atmospheric pressure in order to investigate the influence of gas bubbles on the material removal rate. EDM experiments were conducted on drilled holes. Machining results shows that the material removal per pulse in consecutive pulse discharges slightly decreased as the external pressure increased. This is probably because under the lower pressure, the boiling point of the electrode materials decreases. In addition, under optimal pressure, the feed of tool electrode was stable and the material removal rate was largest. This is because the sufficient large bubbles enhance the flushing of the dielectric liquid contaminated with debris particles and gas bubbles in the machining gap.