Effect Of Electrical Discharge Machining Research Articles

Surface integrity of Ti-6Al-4V alloy in hybrid electrical discharge machining processes

Titanium alloy is one of the difficult-to-machine materials. The final conditions of the machined surface of this alloy are influenced by electro-discharge machining. High temperatures and thermal cycles in machining operation induce undesirable alterations in the surface quality of Ti-6Al-4V. One of the ways to improve the negative effects of electrical discharge machining is to use hybrid methods. There is no comprehensive research on the effect of hybrid electrical discharge machining process on the surface integrity of the Ti-6Al-4V alloy. In this paper, hybrid electrical discharge machining techniques including ultrasonic-assisted electrical discharge machining, powder-mixed dielectric electrical discharge machining using Al2O3 nanopowders and powder-mixed dielectric combined with ultrasonic-assisted electrical discharge machining, were used for processing of this alloy. The hybrid electrical discharge machining processes were evaluated by basic specifications of surface integrity including surface cracks, heat affected area, residual stress, and corrosion resistance. It was found that in powder-mixed dielectric combined with ultrasonic-assisted electrical discharge machining process, developed microcracks were very low and this process developed a thinner heat-altered layer, compared to traditional electrical discharge machining process, which produced a thicker heat-altered layer. The findings also, demonstrated that ultrasonic waves have reduced residual stresses compared to other methods and its stress diagram was distinct in comparison with the other processes. The corrosion rate of samples machined by electrical discharge machining process was higher than other hybrid processes; in powder-mixed dielectric electrical discharge machining process, the machined samples had the highest corrosion resistance.

Investigation on the effects of electrical discharge machining on mild steel surface texture and its corrosion behaviour in NaCl solutions

Investigation on the effects of electrical discharge machining on mild steel surface texture and its corrosion behaviour in NaCl solutions

Effect of Electrical Discharge Machining on Surface Roughness of Cylindrical Shaped Parts

This paper introduces an experimental study on the influence of electrical discharge machining (EDM) cylindrical shaped parts made of 90CrSi tool steel. In this work, some experiments were designed and analysed based on Taguchi method. Also, four input parameters including the pulse on time, the pulse off time, the current, and the server voltage were investigated. The influence of these parameters on the surface roughness were estimated by analysing variance. In addition, the optimum input parameters were found for getting the minimum surface roughness.

The surface integrity of ultra-fine grain steel, Electrical discharge machined using Iso-pulse and resistance–capacitance-type generator

Ultra-fine grained materials with high strength and low weight are eventually considered to be used in industries. To produce ultra-fine grained materials, equal channel angular pressing is a functional method, imposing severe plastic deformation on the workpiece. Electrical discharge machining is an indispensable process in manufacturing industrial parts with high accuracy and precision. However, electrical discharge machining has thermo-physical consequences, damaging the surface layers of the workpiece. On the other hand, the ultra-fine grained materials are thermodynamically unstable and tend to microstructural evolution. Thus, electrical discharge machining process affects the ultra-fine grained materials more than coarse grain materials. In this study, the effects of electrical discharge machining on the ultra-fine grained steel were investigated and the undesirable influences of the electrical discharge machining were diminished by adjusting the electrical discharge machining parameters. The ultra-fine grained steel samples were electrical discharge machined in two methods including Iso-pulse (roughing mode and finishing mode) and with resistance–capacitance-type generator. The surface integrity parameters, including thickness and microstructure of the recast layer and heat-affected zone, the cracks density and hardness, which for all three types of samples, were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction technique, and micro-hardness tester. The results show that electrical discharge machining with resistance–capacitance-type generator has the minimum effects on the surface integrity of the ultra-fine grained samples because of the different material removal mechanism of resistance–capacitance-type electrical discharge machining.

MULTI-OBJECTIVE OPTIMIZATION OF EDM PROCESS PARAMETERS FOR MACHINING OF HYBRID ALUMINUM METAL MATRIX COMPOSITES (Al7075/TiC/B4C) USING GENETIC ALGORITHM

This study deals with the investigation on the effect of Electrical Discharge Machining (EDM) parameters during machining of hybrid composite (Al 7075/TiC/B4C). The optimum process parameters of die sinking EDM like pulse current, pulse duration and gap voltage on metal removal rate, tool wear rate and surface finish were investigated. Full factorial experimental design was selected for experiments. Analysis of variance was employed to study the influence of process parameters and their interactions on response variables. Among the process parameters considered, it was observed that the pulse current was found to be more influential in affecting MRR, TWR and SR. The other parameters have little effect on the response variable. Multi-objective optimization study was also performed using genetic algorithm to find the optimum parameter setting for controversial objective function combination such as high MRR and low SR and High MRR and low TWR. Scanning electron microscope study was performed to study the surface characteristics.

Enhancement the Thermal Effects Produce by EDM Using Hybrid Machining

The present work is aimed to improve the thermal effects of electrical discharge machining (EDM) by EDM/ECM hybrid process. A hybrid method of EDM-ECM combined processing involve EDM shaping as well as electrochemical machining (ECM) finishing, also, they are conducted in sequence one same machine tool, same electrode, yet on the different dielectric. Concerning the process of EDM, the material will be removed via the vaporization and melting throughout all electric discharges. Thus, thermally damaged layers make the machined surface. In this study, the used workpiece material is the A2-Tool Steel material, while the electrode material is copper. The influence of controllable parameters could be identified via RSM, which is an abbreviation for Response surface methodology, these controllable effects include: pulse current, pulse on time, pulse off time, gap, voltage, and electrolyte concentration on white layer thickness (WLT) and Surface Roughness (SR). It has been noticed that model adequacy is acceptable because the coefficient of determination is closest to one for WLT and SR, in addition to that, the generated surface doesn’t have thermally affected layers as the SR and recast layers which have been generated via EDM are removed entirely through ECM finishing.

Effect of Electrical Discharge Machining and Shot Blast Peening Parameters on Fatigue Life of AISI D2 Die Steel

The present paper deals with studying the effect of electrical discharge machining (EDM) and shot blast peening parameters on work piece fatigue lives using copper and graphite electrodes. Response surface methodology (RSM) and the design of experiment (DOE) were used to plan and design the experimental work matrices for two EDM groups of experiments using kerosene dielectric alone, while the second was treated by the shot blast peening processes after EDM machining. To verify the experimental results, the analysis of variance (ANOVA) was used to predict the EDM models for high carbon high chromium AISI D2 die steel. The work piece fatigue lives in terms of safety factors after EDM models were developed by FEM using ANSYS 15.0 software. The results appeared that the experimental fatigue safety factors (at 106 cycles) decreased by (11 %) after EDM using copper electrodes compared with as-received material and this value is higher by (3.35 %) when using graphite electrodes. The fatigue strength at the same number of cycles was (0.88) and (0.84) times the fatigue strength of as-received material for copper and graphite electrodes respectively. While fatigue strength and safety factors increased after EDM when increasing shot peening time, at the higher shot peening time is by (19.1 %) when using copper electrodes and by (23.26 %) when using graphite electrodes.

Effect of electrical discharge machining on dental Y-TZP ceramic-resin bonding

PurposeThe study determined (i) the effects of electrical discharge machining (EDM) on the shear-bond strength (SBS) of the bond between luting resin and zirconia ceramic and (ii) zirconia ceramic's flexural strength with the three-point bending (TPB) test. MethodsSixty 4.8mm×4.8mm×3.2mm zirconia specimens were fabricated and divided into four groups (n=15): SBG: sandblasted+silane, TSCG: tribochemical silica coated+silane, LTG: Er:YAG laser treated+silane, EDMG: EDM+silane. The specimens were then bonded to a composite block with a dual-cure resin cement and thermal cycled (6000 times) prior to SBS testing. The SBS tests were performed in a universal testing machine. The SBS values were statistically analyzed using ANOVA and Tukey's test. To determine flexural strength, sixty zirconia specimens were prepared and assigned to the same groups (n=15) mentioned earlier. After surface treatment TPB tests were performed in a universal testing machine (ISO 6872). The flexural strength values were statistically analyzed using ANOVA and Tukey's test (α=0.05). ResultsThe bond strengths for the four test groups (mean±SD; MPa) were as follows: SBG (Control), 12.73±3.41, TSCG, 14.99±3.14, LTG, 7.93±2.07, EDMG, 17.05±2.71. The bond strength of the EDMG was significantly higher than those of the SBG and LTG (p<0.01). The average flexural strength values for the groups SBG (Control), TSCG, LTG and EDMG were 809.47, 800.47, 679.19 and 695.71MPa, respectively (p>0.05). ConclusionsThe EDM process improved the SBS. In addition, there was no significant adverse effect of EDM on the flexural strength of zirconia.

Surface Alloying by Powder Metallurgy Tool Electrode Using EDM Process

In this study, electrical discharge alloying (EDA) is used to modify the surface of high carbon steel En31 with the help of tool electrode (Copper-Chromium-Nickel) manufactured by powder metallurgy (PM) process. The effect of Electrical Discharge Machining (EDM) parameters on micro-hardness during surface alloying is studied. Design of experiment (DOE) using Taguchi method and L18 orthogonal array is used to find the best level of process parameters in order to achieve high micro-hardness. Six processing parameters; including tool polarity, percentage of alloying element in tool, peak current, pulse on-time, duty factor, and voltage, are considered and their significance is investigated by analysis of variance (ANOVA). Experimental results show the increase in micro-hardness of the machined surface by 139.7% as compared to the base material. Additionally, techniques like Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) are used to analyze the change in composition of alloying elements and phases of the machined surface. It is concluded that the increase in micro-hardness is due to the formation of carbides containing chromium in the alloyed layer.

Effect of Electrical Discharge Machining on strength and reliability of WC–30%Co composite

Tungsten carbide/Cobalt (WC–Co) composite is one of the important composite materials, which is used for manufacturing of cutting tools, dies and other special tools. It has very high hardness and excellent resistance to shock and wear. It is not possible to machine this material easily with conventional machining techniques. Due to the good electrical conductivity of WC–Co, it is usually machined by Electrical Discharge Machining (EDM). EDM process often results in the surface damage of bulk WC–Co, and the influence of the damage would affect the reliability. It is important to investigate the effect of electric discharge machining process on the properties of WC–Co cemented carbides before applying its engineering application. For these composites, maintenance of proper fracture strength is an important concern and is to be controlled. In this work, an attempt has been made to investigate the fracture strength and the reliability of EDMed WC–Co composite using the Weibull distribution analysis. The comparison of results between the machined composites and un-machined composites is carried out and presented in this study.

Optimization of Machining Parameters in Electrical Discharge Machining (EDM) of 304 Stainless Steel

In this investigation, the effect of electrical discharge machining (EDM) parameters such as pulse-on time (TON), pulse-off time (TOFF), Voltage (V) and Current (I) on material removal rate (MRR) in 304 Stainless steel was studied. The experiments are carried out as per design of experiments approach using L9 orthogonal array. The results were analyzed using analysis of variance and response graphs. From this study, it is found that different combinations of EDM process parameters are required to achieve higher MRR for 304 Stainless steel. Signal to noise ratio (S/N) and analysis of variance (ANOVA) is used to analyze the effect of the parameters on MRR and also to identify the optimum cutting parameters. The contribution of each cutting parameters towards the MRR is also identified. The results from this study will be useful for manufacturing engineers to select appropriate EDM process parameters to machine Stainless steel 304.

Adopting Three-Level Inverter to Solve the Bearing Fault of Roll Forming

During the roll forming factory, the front bearing of AC motor was always malfunction. The problem was that there was large axial vibration and the deterioration was in the trend of rapid development. In order to make early preparations for repairs and maintenance to determine the basis for decision-making, the motor bearings were under monitoring when running. In AC drive systems, bearings are more likely to be damaged from the highly accelerated/decelerated operation and the effects of electrical discharge machining resulting from high dv/dt, which are introduced by PWM input voltage. Multi-level inverters offer better sinusoidal voltage waveform than 2-level inverters due the fact that output voltage can be formed using more than two voltage level. This causes the THD to be lower. Switching losses are reduced because switching frequency can be lower than in 2-level inverter. According the testing data analysis, bearing had been replaced with 3-level AC inverter and maintenance of the response had been decided.

A19 放電加工成形された微細軸の強度評価とその極小径切削工具製作への応用(OS8 放電加工(2))

Few studies have been carried out on the effect of electrical discharge machining (EDM) conditions on the strength of workpieces processed by micro-EDM. The bending strength of cemented tungsten carbide 5-μm-diameter micropins fabricated by micro-EDM was therefore investigated. Although the bending strength increased with a decrease in the electrical discharge energy at the finish machining of micropins, it decreased at smaller discharge energy. The result of the bending strength test was then applied for the EDM fabrication of cemented tungsten carbide ultrasmall-diameter cutting tools. Tools with a long tool life were successfully fabricated.

The effect of process parameters on machining of magnesium nano alumina composites through EDM

The effects of electrical discharge machining (EDM) parameters on drilled-hole quality such as taper and surface finish are evaluated. Microwave-sintered magnesium nano composites (reinforced with 0.8 and 1.2 wt.% of nano alumina) are used as work materials. Experiments were conducted using Taguchi methodology to ascertain the effects of EDM process parameter. The process parameters such as pulse-on time, pulse-off time, voltage gap, and servo speed were optimized to get better surface finish and reduced taper. ANOVA analyses were carried out to identify the significant factors that affect the hole accuracy and the surface roughness. Confirmation tests were performed on the predicted optimum process parameters. Pulse-on time and the servo speed are identified as major response variables. Micro structural changes and the effects of nano particle reinforcement in the drilled hole were studied through SEM micrographs.

Effect of electrical discharge machining process on crack susceptibility of nickel based heat resistant alloy

The objective of this study was to investigate the effects of electrical discharge machining (EDM) process conditions on the crack susceptibility of a nickel-based superalloy. Because sequential processes are inevitable in the manufacturing industry, the effects of EDM and post-EDM processes on the crack propagation behaviour of the components need to be clearly understood. The altered material zone (AMZ) of EDM processed Hastelloy X revealed different morphology before and after solution heat treatment. Depending on the EDM dielectric fluid and the post-EDM process such as solution heat treatment, it was found that cracks existing in the recast layer could propagate into substrate when a 20% strain tensile force was applied at room temperature. In the case of the kerosene electrical discharge (ED) machined specimens, it was observed that carburisation and sharp crack propagation along the grain boundary occurred after the heat treatment. However, the deionised water ED machined specimens after heat treatment underwent oxidation and showed no crack propagation behaviour. A metallurgical evaluation of the microstructure of the AMZ was also conducted.

Effect of electrical discharge machining on surface characteristics and machining damage of AISI D2 tool steel

In this work the electrical discharge machining (EDM) of AISI D2 tool steel was investigated. The surface characteristics and machining damage caused by EDM were studied in terms of machining parameters. Based on the experimental data, an empirical model of the tool steel was also proposed. A new damage variable was used to study the EDM damage. The workpiece surface and re-solidified layers were examined by a scanning electron microscopy. Surface roughness was determined with a surface profilometer. The residual stress acting on the EDM specimen was measured by the X-ray diffraction technique. Experimental results indicate that the thickness of the recast layer, and surface roughness are proportional to the power input. The EDM process introduces tensile residual stress on the machined surface. The EDM damage leads to strength degradation.

EDM surface effects on the fatigue strength of a 15 vol% SiC p/Al metal matrix composite material

The effects of electrical discharge machining (EDM) on the surface quality and subsequent performance of a 15 vol% SiC particulate reinforced A356 Al under monotonic and fatigue loading conditions are investigated. Surface and subsurface conditions after EDM surface sparking of the material were compared with the same material after careful surface polishing. Tensile tests were performed on the as-received material and the EDM surface sparked material to ascertain effects of EDM processing on basic monotonic properties. High cycle constant stress amplitude fatigue tests were conducted on the polished material and on the sparked material, and fractographic analysis was performed to study the mechanisms of fatigue fracture. EDM sparking was found to dramatically increase surface roughness and cause slight subsurface softening in the microstructure below the outer recast layer. Fatigue strength is notably reduced by EDM processing, with greater degradation resulting from higher material removal rates (MRRs).

Effect of electrical discharge machining on the characteristics of carbon fiber reinforced carbon composites

This work investigated electrical discharge machining (EDM) of carbon fiber reinforced carbon composite material. The characteristics of composites machined by EDM were studied in terms of machining parameters. An empirical model of the composites was also proposed based on the experimental data. The composite material was produced by an electrical discharge sinker using a graphite electrode. The workpiece surface and resolidified layers were examined by scanning electron microscopy (SEM). Moreover, surface roughness was determined with a surface profilometer. Experimental results indicate that the extent of delamination, thickness of the recast layer, and surface roughness are proportional to the power input. The EDM process effectively produces excellent surface characteristics and high quality holes in composites under low discharge energy conditions.