Spark Gap Voltage Research Articles

Wire Electric Discharge Machining Induced Surface Integrity for Ni55.95Ti44.05 Shape Memory Alloy

The current study unveils the variation of surface integrity aspects (micro-hardness, surface crack density, and surface characteristics) for Ni55.95Ti44.05 shape memory alloy (SMA) with wire electric discharge machining (WEDM) process parameters, namely, pulse off time, wire tension, spark gap voltage, wire feed rate and pulse on time. The experimental results reveal that micro-hardness displays direct relationship with spark gap voltage, pulse on time, and pulse off time whereas surface crack density shows direct relationship with pulse on time and inverse trend with spark gap voltage and pulse off time. Wire tension and wire feed rate show trivial effect on both surface crack density and micro-hardness. Machined surface comprises crater, micro-cracks, micro-voids, pockmarks, and lumps of debris while inspecting through a scanning electron microscope (SEM). During energy-dispersive X-ray spectroscopy (EDS) analysis, the foreign elements namely carbon, oxygen, copper and zinc were also detected on the surface. The high energy density at higher pulse on time adversely affects the surface morphology. The formation of large size craters (deep and wide) with more cracks on the machined surface were observed at lower pulse off time as compared to higher pulse off time.

Empirical Investigations during WEDM of Ni-27Cu-3.15Al-2Fe-1.5Mn Based Superalloy for High Temperature Corrosion Resistance Applications.

Monel K-500, a nickel–copper based alloy, is a very hard and tough material. Machining of such hard and tough materials always becomes a challenge for industry and this has been resolved by wire electric discharge machining (WEDM), a popular non-conventional machining method used for machining tough and hard materials having complex shapes. For the first time reported in this present research work is an experimental investigation executed on Ni-27Cu-3.15Al-2Fe-1.5Mn based superalloy using WEDM to model cutting rate (CR) and surface roughness (SR) using response surface methodology (RSM). The process parameters have been selected as pulse-on time, pulse-off time, spark-gap voltage and wire-feed rate. Experiments have been planned according to the central composite design (CCD). The results show that pulse-on time has a direct effect on CR while the pulse-off time has a reverse effect. The CR increases as pulse-on time increases, and decreases as pulse-off time increases. SR increases as pulse-on time increases, and decreases as pulse-off time increases. Furthermore, increase in spark-gap voltage decreases CR and SR both. The wire feed-rate has a negligible effect for both the response parameters. The optimized values of CR and SR achieved through multi-response optimization are 2.48 mm/min and 2.12 µm, respectively.

Optimization of machine machining parameters in EDM of silicon nitride-titanium nitride based on RSM

EDM of silicon nitride–titanium nitride ceramic composites with copper electrode was carried out here. Input factors of outstanding significance like current (I), spark gap voltage (SV), pulse-on duration (T on ) and pulse-off duration (T off ) were selected to calculate listed technological characteristics. The output responses measured were material abrasion loss (MRR) and electrode abrasion rate (EWR). Also, the distinguishing face of the EDM technique is delved by RSM (Box-Benhken method) based on Design of Experiments (DOE) and experimental results are evaluated by Analysis of Variance (ANOVA). Furthermore, L 29 orthogonal array (OA) based on the DOE to carry a row of machining has been followed here. From experimental outcomes, it is apparent that the current is the highly significant parameter among other factors as it alters both material abrasion loss and electrode abrasion rate. On the other part, difference in the pulse-off duration did not affect the responses. The higher material abrasion loss is obtained when current and pulse-on duration is higher and the increased gap voltage and lower current reduces the EWR. The higher MRR is obtained for current – 6 amps, pulse-on duration – 7 µsec, pulse-off duration – 10 µsec and spark gap voltage – 35 V. Reduced EWR is obtained for current – 4 amps, pulse-on duration – 6 µsec, pulse-off duration – 10 µsec and spark gap voltage – 40 V.

A Multi Criteria Decision Making (MCDM) based on TOPSIS and RSM for process improvement in electrical discharge machining of silicon nitride–titanium nitride ceramic composites

This experiment is an attempt to choose the optimal machining parameters for electrical discharge machining (EDM) of silicon nitride–titanium nitride (Si3N4–TiN) ceramic composites based on MCDM approach. The electrical discharge machining have been conducted according to L21 orthogonal array with preferred input parameters like current (I), spark gap voltage (SV), pulse-on duration (Ton) and pulse-off duration (Toff). The response parameters measured are material eradication rate (MRR), electrode eradication rate (EWR) and surface roughness (Ra). The MCDM techniques namely Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and Response Surface Methodology (RSM) are used to find the optimal machining parameters which provide better value of all responses. Also, scanning electron microscopy (SEM) is employed for examining the surface defects like micro-cracks, micro-pores, droplets, surface craters, globules, etc.

Mathematical Modeling and Optimization of Wire Electric Discharge Machining Parameters on Inconel 825 Using Desirability Method

The present research work mainly emphases on experimentation, analysis and optimization of machining parameters during WEDM on Inconel 825. Based on Box-Behenken Design, 29 experimental runs were executed on WEDM using 0.25 mm dia half hard brass wire and de-ionized water as dielectric. Controllable parameters pulse on time (Ton), pulse off time (Toff), spark gap voltage (SV) and wire feed (WF) are varied up to three levels to study their influence on response measures cutting speed (CS) and gap current (Ig). Experimental models were developed by employing RSM. Design expert software 7.0.0 was considered for design of experiments and developing the mathematical model. Graphical model analysis has been done with the help of Analysis of Variance (ANOVA). Ton Toff and SV have major influencing factors on responses where, as wire Feed was insignificant. To achieve optimal parameter combination, multi-objective optimization of responses is performed using desirability method. Confirmation test is performed at optimal combination of parameters provided by desirability function to validate the study. Hence, predicted value lies in correspondence with the experimental findings.

Optimization of WEDM process parameters for machining Al 2219 alloy

Aluminum alloy characterized by superior material properties require non conventional machining methods before being put to use in aerospace and automobile applications. This paper details the influence of process parameters (control factors) namely pulse on time, pulse off time and spark gap voltage on the cutting speed (response) in wire-electrical discharge machining of Al 2219 alloy specimen by implementing Box-Behnken design (BBD) experimentation array adopted for Response Surface Methodology technique. Three levels for each of the control factors necessitated 17 experimental runs for subsequent analysis. It was established that cutting speed varied directly with pulse on time and spark gap voltage but inversely with pulse off time. Optimal cutting speed of 0.806 mm3/min was determined for a unique factor combination of pulse on time (Ton) of 124.27 µs, pulse off time (Ton) of 51.498 µs and spark gap voltage (SV) of 40.547 V.

Parametric optimization of WEDM for EN AW 7075 alloy processed by ECAP

This study discusses the experimental investigation on WEDM of EN AW 7075 alloy deformed severely plastically by Equal Channel Angular Extrusion (ECAP). Experimentation has been executed by varying pulse-on time (Ton), pulse-off time (Toff), peak current (IP) and spark gap voltage (SV). The influence of these parameters was studied on the kerf width (KW), machining speed (MS). The set of machining parameters for experiments were prepared using central composite design (CCD) followed by response surface methodology (RSM). Optimization was carried out using Genetic algorithm. From machining performance analysis it can be inferred that longer pulse-on time which causes greater discharge energy, affects the most on the response parameters, hence leading to a higher amount of material removal causes an increase in machining speed and kerf width.

Analysis of electrical discharge machining parameters for H13 steel using OVAT technique

Electrical discharge machining (EDM) is the most dominant innovation in the field of non-traditional machining for the processing of difficult-to-machine materials. This practice considerably improves the machining characteristics by increasing material removal rate, surface hardness together with the reduced surface roughness and tool wear rate. In the present study, one-variable-at-a-time (OVAT) approach was employed to investigate the input machining parameters for H13 steel with copper tool. The effectiveness of input parameters evaluated in terms of material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR), opted as output responses. It was observed experimentally that discharge current 9 A, pulse-on duration 250 μs and spark gap voltage of 50 V notably influence the machining characteristics of H13 steel with copper tool.

Microstructural analysis and multi response optimization of WEDM of Inconel 825 using RSM based desirability approach

AbstractIncreasing demand of aerospace industry for more heat resistant and tough material have open up the possibility of the use of Inconel 825 for making of combustor casing and turbine blades. Because of its robust nature, Inconel 825 is a difficult-to-cut material with conventional methods. Wire-cut electrical discharge machining (WEDM), a non traditional method uses thermoelectric erosion principle to produce intricate shape and profiles of such difficult-to-cut material. In this study, various operating parameters of WEDM are optimized using desirability approach and microstructural behavior at optimum combinations was studied. Input parameters viz. pulse-on time, pulse-off time, peak current, spark gap voltage, wire tension, wire feed and performance has been measured in term of material removal rate, surface roughness and wire wear ratio. It has been observed that at 110 machine unit pulse-on time (Ton), 35 machine unit pulse-off time (Toff), 46 volt gap voltage (SV), 120 ampere peak current (IP), 11 machine unit wire tension (WT) and 5 m/min wire feed (WF), the values obtained for material removal rate (MRR), surface roughness (SR) and wire wear ratio (WWR) were 27.691mm2/min, 2.721 μmand 0.117 respectively. Scanning electron microscopy, energy dispersive spectrograph and X-ray diffraction analysis has also been carried out to study the surface characterization. Comparatively less numbers of cracks, pockmarks, craters, and pulled out material were found on work specimen surface and wire electrode surface under standardized conditions, thus maintaining the surface integrity of the machined surface.

Multi-Objective Optimization of Machining Process Parameters in Wire-Cut Electric Discharge Machining of Inconel X750 Alloy by Combinatorial Approach

Difficult-to-cut materials, generally high hardness, strength and toughness, are generally difficult to machine in conventional machining. Also tool wear is high in conventional machining processes. Wire Cut Electric Discharge (WEDM) machining is particularly used for machining complex profiles, demanding very high accuracy. The current work focuses on the optimization of roughness of a surface that is machined using WEDM; the process parameters considered for optimization are pulse-on-time (Pon), pulse-off time (Poff), wire feedrate (WFR) and spark gap voltage (SGV). One of the surface integrity aspect is considered as surface roughness (SR) and other related to machining output considered as material removal rate (MRR) for the output responses. The paper presents, a multi-criteria decision making technique, with Grey Relational Analysis (GRA) integrated with Particle Swarm Optimization (PSO) for optimizing the process parameters. Further, confirmation tests that were conducted also validated the improvement in SR and MRR.

Investigation of dimensional deviation in wire EDM of M42 HSS using cryogenically treated brass wire

High speed steel is self-hardening steel which has excellent fracture toughness, and resistance to shock. Therefore, an attempt has been made to study the dimensional deviation in wire EDM of M42 HSS using cryogenically treated brass wire. The ANOVA test was also conducted to reveal the significant factors of the process. The ANOVA test for dimensional deviation revealed pulse-off-time, pulse-on-time, and spark gap voltage as the crucial variables for the response studied. The DD's optimized parameter setting is as; pulse off time – 49 mu, pulse on time – 113 mu, wire feed – 6 m/min, and spark gap voltage – 60 V. The confirmatory result showed that the variation of around 3.15% from the predicted value.

Parametric Optimization of WEDM Characteristics on Inconel 825 using Desirability Research

The present research focuses on the optimization of wire-cut electric discharge machining (WEDM) parameters. In this study, RSM based multi-response desirability method is used to optimize the WEDM characteristics for single and multiple responses. Input parameters of WEDM viz. pulse-on time, pulse-off time, spark gap voltage, wire tension, peak current, wire feed and performance was measured in terms of material removal rate (MRR) and surface roughness (SR). WEDM is a nontraditional method uses the spark erosion principle to produce the intricate shape and profiles of difficult-to-cut material. Inconel 825 is increasing in demand in the aerospace industry for more heat resistant and tough material. Because of its robust nature, it is difficult to be machined with conventional methods. WEDM is best alternate to overcome this problem. It has been observed that at Ton 111 MU, Toff 35 MU, SV 46V, IP 140A, WT 9 MU and WF 6 m/min, the values obtained for MRR and SR are 32.015mm2/min and 2.528 μm respectively.

Processing of curved profiles on Ni-rich nickel–titanium shape memory alloy by WEDM

ABSTRACTIn wire electrical discharge machining (WEDM) process, to the machine, sharp corner without error is an extremely challenging issue which is vital for precision machining. Owing to the presence of huge wire deflection, the accuracy of the machined corner is undesirably affected. The aim of this study is to explore the effect of process parameters namely, spark on time, spark off time, wire tension, wire feed rate, and spark gap voltage on corner error for acute angle (60°), right angle (90°) and obtuse angle (120°) triangular profiles during WEDM of Ni50.89Ti49.11 shape memory alloy (SMA). Owing to the effect of discharge concentration, corner error for acute angle profile is predominantly affected by spark on time, spark off time, and spark gap voltage. Wire tension was the most influencing parameter for corner error of obtuse and right angle profile due to the effect of wire deflection and wire vibration, whereas wire feed rate has trivial effect for all type of profile. In order to reduce the corner error, pulse modification technique was utilized. At low pulse parameters, corner error for 60°, 90°, and 120° profile was reduced by 43.38%, 31.12%, and 29.04%, respectively, as compared to high pulse parameters.

Study on crater depth during material removal in WEDC of Ni-rich nickel–titanium shape memory alloy

The objective of this experimental investigation is to reveal the individual effect of wire electrical discharge cutting (WEDC) process parameters, namely discharge energy density, wire feed rate, spark frequency, wire tension, and spark gap voltage on average crater depth, material removal rate (MRR), and metallographic changes of Ni55.95Ti44.05 shape memory alloy (SMA). The analysis of crater size during material removal in WEDC has been also discussed in this study. The three-dimensional surface topography at higher discharge energy density divulges the formation of deeper and wider craters with high surface roughness on the machined surface compared to lower discharge energy density. MRR and average crater depth increase with the increase in discharge energy density and decrease with the increase in spark frequency and spark gap voltage, whereas wire feed rate and wire tension have the trivial effect. The analysis of X-ray diffraction peaks of the machined surface shows the presence of various compounds such as NiTi, TiO, TiO2, Ni4Ti3, CuZn, Cu2NiZn, NiTiO3, and NiZn and tensile residual stress.

Modelling of surface characteristics of wire-electro discharge machined combustor material specimens

Current research discusses the experimentation on WEDM of combustor material (i.e. nimonic 263) with varying pulse-on time (Ton), pulse-off time (Toff), peak current (Ip) and spark gap voltage (Sv). The influence of parameters is evaluated on the basis of material removal rate (MRR) and surface roughness (SR). Experimental runs are designed according to user-defined RSM. 81 experiments are executed under different parametric conditions. RSM based desirability approach is applied to find out the optimal parameters for maximizing MRR and minimize Sr After that, experimental results are utilized to train the neural network. Furthermore, microstructure changes and composition of WEDMed surface is assessed by FE-SEM. It is observed that WEDMed surfaces contain micro-cracks, craters, spherical droplets and lump of debris. In addition, the mechanism of recast layer formation and microhardness of machined surfaces are critically evaluated to apprehend better understanding of the technique. Furthermore, polishing was considered as a post-processing technique for removing the RLT. The key features of experimental procedure are also highlighted in this paper.

Surface finish analysis of wire electric discharge machined specimens by RSM and ANN modeling

This study discusses the experimental investigation on WEDM of combustor material (i.e. nimonic 263). Experimentation has been executed by varying pulse-on time (Ton), pulse-off time (Toff), peak current (Ip) and spark gap voltage (Sv). The influence of these parameters was studied on the Surface roughness parameters (i.e., average: Ra and ten-point mean: Rz), recast layer thickness (RLT), and changes in the machined surface. Experiments are designed as per Box-Behnken design technique. Parametric optimization has also been performed using response surface methodology. The results of proposed algorithm show that the BPNN is effective tool for the prediction of responses. The BPNN predicted results are 99% in agreement with the experimental results. Furthermore, microstructure and composition of WEDMed surface was assessed by FE-SEM. It was observed that WEDMed surfaces contain micro-cracks, craters, spherical droplets and lump of debris. Longer pulse-on time causes greater discharge energy, hence leading to higher material removal rate, surface roughness, and recast layer thickness. In addition, the mechanism of recast layer formation and microhardness of machined surfaces have been critically evaluated to apprehend better understanding of the technique. Furthermore, polishing was considered as a post-processing technique for removing the RLT. The key features of experimental procedure are also highlighted.

Modeling and optimization of Wire-EDM parameters for machining of Ni55.8Ti shape memory alloy using hybrid approach of Taguchi and NSGA-II

In the present research, Ni55.8Ti shape memory alloy has been machined by wire electric discharge machining (wire-EDM) process. The effects of input parameters such as spark gap voltage, pulse on-time, pulse off-time, and wire feed on productivity, i.e., metal removal rate (MRR) and surface quality, i.e., mean roughness depth (Rz), have been investigated. Empirical modeling and ANOVA study have been done after conducting 16 experiments based on Taguchi’s L16 design of experiment technique. Ranking and crowding distance–based non-dominated sorting algorithm-II (NSGA-II) is used for process optimization. The error percentage varies within ± 6% between experimental results and the predicted results developed by NSGA-II. It has been observed that the wire-EDM machining of Ni55.8Ti alloy at optimum parameters resulted in improved MRR —0.021 g/min—and surface quality with good surface finish (Rz—6.2 μm) and integrity as significant reduction in the formation of cracks, lumps, and deposited layers.

Modelling and analysis for the machinability evaluation of Udimet-L605 in wire-cut electric discharge machining

The intention of this research is to examine and analyse the machinability of Udimet-L605 in wire-cut electric discharge machining. The pulse-on time, pulse-off time, peak current, wire tension, spark gap voltage, wire feed have been considered as input variables and two response variables as material removal rate and surface roughness. The four models, such as support vector machine using two different kernels, nonlinear regression and multi-linear regression have been proposed to check the variation among the experimental and predicted consequences. In addition to this, the sensitivity analyses test has been performed on prominent model to examine the influence of input variables on the material removal rate and surface roughness in wire electric discharge machining and epitomised that pulse-on time is the momentous parameter for both material removal rate and surface roughness. The support vector regression based on the polynomial kernel model has conferred enhanced resulting in a contest with other models.

Modeling and desirability approach-based multi-response optimization of WEDM parameters in machining of aluminum metal matrix composite

The study presents machining aspects of particulate silicon carbide reinforced aluminium metal matrix composite (Al/SiCp-MMC) using wire-cut electric discharge machining process. The influences of process parameters such as pulse on time, pulse off time, spark gap voltage, peak current, wire tension and wire feed rate on response variables such as workpiece cutting speed, surface roughness (Ra) and spark gap have been investigated. The Box–Behnken’s design has been utilized to plan the experiments, and response surface methodology is employed for developing quadratic regression models for selected response variables. Desirability function approach has been used to solve the multi-response optimization problem by assigning the weightages to the selected responses as per the user’s requirement of quality or productivity. The study recommends optimal process conditions such as pulse on time 0.75 µs, pulse off time 16 µs, spark gap voltage 35 V, peak current 120 A, wire tension 1200 g, and wire feed rate 10 m/min for effective machining of Al/SiCp-MMC, which has been validated by conducting confirmation experiments. The developed regression models for selected responses revealed compatible results, thereby justifying their acceptability.

Parametric study on the recast layer during EDWC of a Ni-rich NiTi shape memory alloy

Shape memory alloys (SMAs) have exceptional properties, namely, shape memory effect, superelasticity and other enriched physical and mechanical properties. The conventional machining of these alloys is associated with several severe difficulties. Electric discharge wire cutting (EDWC), an advanced machining process, is utilized to machine Ni50.89Ti49.11 SMA under this investigation. The aim of this investigation was to reveal the effect of EDWC variable parameters such as pulse on time ( TON), wire feed (WF) rate, spark gap voltage (SV), wire tension (WT) and pulse off time ( TOFF) on recast-layer thickness (RLT) and a foreign element atomic content (FEAC) using the one-factor-at-a-time approach. Scanning electron microscope equipped with energy dispersive X-ray spectroscopy facility was utilized to analyse RLT and FEAC. RLT and FEAC are varied linearly and nonlinearly respectively with TON, TOFF and SV. A thick recast layer with a high percentage of FEAC was formed on the machined surface of Ni50.89Ti49.11 SMA at a higher TON and a lower TOFF and SV. However, RLT and FEAC are slightly varied with WF and WT.