# Introduction t is clear that the past few years have seen an increasing interest in the novel applications of electrical discharge machining to see the potential of this technique for better process performances it is obvious that lot of work has been done to optimize the EDM process and the work related to finding the feasibility of harder material. The correct selection of manufacturing conditions is one of the most important aspects to take into consideration in the majority of manufacturing processes and, particularly, in processes related to Electrical Discharge Machining (EDM). It is a capable of machining geometrically complex or hard material components, that are precise and tool steels, composites, super alloys, ceramics, carbides, heat resistant steelspulse on time and diameter of tool of En-19 tool steel material. Parts of the experiment were conducted with the L18 orthogonal array based on the Taguchi method . And non-conventional machining. The Electric discharge machining process is finding out the effect of machining parameter such as discharge current, materials, posses greater strength and toughness are usually known to create major challenges during conventional forming tools. These steel are categorized as difficult to machine rang of application in Plastic moulds, frames for plastic pressure dies, hydro better polish ability, it has a grooving tempered condition. Good mach inability, hardened and as preferred particle size, sintering temperatures and pressures. Despite the promising results, electric discharge and nuclear industries. En-19 Plastic mould steel that is usually supplied in a making industries, aerospace, aeronautics etc. being widely used in die and mold. 1. To find feasibility of machining EN-19 tool steel using U-shaped tubular copper electrode and internal flushing. 2. To analyze the responses MRR, TWR, and over cut by using the machining parameter selected for discharge current, pulse on time, and diameter of the tool using Taguchi design approach. 3. To Find the influence of MRR With discharge current, pulse duration time, and diameter of the tool. To find the influence tool wear rate with discharge current, pulse on time and diameter of tool. 4. To find the influence on over cut with discharge current, diameter of the tool and, pulse on time. 5. To investigate the machining parameters for EDM using shaped electrode of EN-19 tool steel. # II. Parameters Affecting Performance of Edm # b) Peak Current Higher amperage is used in roughing operations and in cavities or details with large surface areas. Machined cavity is a replica of tool electrode and excessive wear will affect the accuracy of machining. # c) Pulse Duration and Pulse Interval Each cycle has an on-time and off-time that is expressed in units of microseconds. Since all the work is done during on-time, the duration of these pulses and the number of cycles per second (frequency) are important. Pulse on-time is commonly referred to as pulse duration and pulse off-time is called pulse interval. When the optimum pulse duration for each electrodework material combination is exceeded, material removal rate starts to decrease. # d) Polarity Polarity determines the direction of current flow relative to electrode; it can be either positive or negative depending on applications. In positive or normal polarity workpiece is positive and tool is negative and in reverse or negative polarity workpiece is negative and tool is positive. # Pulse waveform of controlled pulse generator e) Dielectric Basic characteristics necessary for a dielectric in EDM are high dielectric strength and quick recovery after breakdown, effective quenching and flushing ability. TWR and MRR are affected by the type of dielectric and the method of its flushing. Generally kerosene and deionized water is used as dielectric fluid in EDM. Tap water cannot be used as it ionizes too early and thus breakdown due to presence of salts as impurities occur. Dielectric medium is generally flushed around the spark zone. It is also applied through the tool to achieve efficient removal of molten material. # f) Pulse-on Time This is time period during which machining is performed. As the 'pulse on' time increases, machining will perform at faster rate and craters will be broader and deeper thereby resulting in poor surface finish and high MRR. Larger the pulse on times means larger is the recast layer and more are the heat affected zones. The 'pulse off' is the time during which reionization of the dielectric takes place. The more is the off time, the greater will be the machining time. The off The experimental set up consists of transparent container in which machining is performed called machining tank, placed in the work tank of EDM. Fixture assembly is used to hold the work piece. Dielectric (kerosene oil) fluid is filled in machining tank. A stirrer system is used to avoid particle setting. Small dielectric circulation pump is used. Pump and stirrer assembly are placed in same tank in which machining is performed. Magnetic forces were used to separate the debris from the dielectric fluid, for these two permanent magnets are placed at the bottom of machining tank. The spark gap is filled with powder particles. When voltage was applied an electric field was created. The powder particles get charged and act as conductors behaving in zigzag manner. # III. # Experimental Design Designing an experiment is the principle need of any experimentation plan. In present study Taguchi Method is used for preparing experimental design. Main steps of experiment plan are listed below. The main objective of this experimentation is to study the effect of current, powder concentration, type of powder and magnetic strength on tool behavior during macro and micro EDM, PMEDM during slot cutting to analyze output parameters dimensional and profile accuracy of tool. # b) Selecting an Appropriate OA The Taguchi method involves reducing the variation in a process through robust design of experiments by using a selected set of experimentation plan. Each factor is assigned column(s) depending on its DOF. Each level of a factor has an equal number of occurrences within each column; and for each level within one column, each level within any other column will occur an equal number of times as well. # c) Selection of Factors Selection of factors is an important task which is to be done carefully to prepare the most effective design of experiment. Brainstorming and pilot experimentations are conducted to decide factors and their levels. Factors and their levels for magnetic assisted PMEDM IV. # Experimental Set Up The experimentation work is performed on T-3822 M Electric Discharge Machine of Victory Electromech placed in non-traditional machining lab at Thapar University, Patiala. A separate arrangement is added for performing powder mixed EDM, a mild steel tank with inside dimensions as length 330 mm, breadth 180 mm, height 187 mm and plate thickness 3 mm. Capacity of the used tank is 9 L. A stirrer with the maximum speed of 1400 rpm is used to properly mix the powder in the dielectric medium. V. # Workpiece and Tool Electrode Details For experimentation, die steel material is used as workpiece. Before machining, workpiece is properly grinded from both the sides for maintain perfect alignment of workpiece with the tool electrode during machining. Three electrode materials used for machining purpose, namely copper, tungsten and C18000 (alloy (Copper, Chromium, Nickel, Silicon (beryllium free)), all with diameter 2.4mm and 30mm length. # Global # Results The effect of powder mixed in dielectric, concentration of powder, current, tool material and pulse-on duration is analyzed on MRR and TWR with and without using external magnetic field. Using Taguchi experimental design, L18 orthogonal array is used for the experiments using bar magnets of 0.1 T. Schematic representation of the tool and the workpiece Tool is made in contact with the workpiece up to 10 mm in length and machining duration is kept 10 minutes. The results are analyzed using ANOVA. It helps in identifying the important process parameters affecting the response. Results for mean of MRR calculated at 90% confidence level ANOVA table for MRR of EN-19 workpiece (Note: For 90% CI, Fcritical(2,6) = 3.46, Fcritical(1,6) = 3.78, PC= percentage contribution) The principle followed by F-test is that, greater is the F value for an input parameter the larger is its effect on output parameter. ANOVA shows the results of MRR of PMEDM with and without the use of magnetic strength. Under such experimental conditions the two factors i.e. tool material (F value 15.56) and current (F value 4.27) are found to be significant. The value of F is for the concentration 1.58 g/L. MRR is found to decrease with concentration because as the amount of powder suspended in the dielectric increases, the circulation of the powder particles is not enough also with increase in concentration above a certain level arcing occurs as the effective gap between the tool and the workpiece decreases with increase in concentration. # Material removal rate (g/min) # Main effects plot of MRR for EN-19 work piece The highest MRR is achieved on suspension of graphite powder as its density and electrical resistivity is least among the all three. The MRR obtained by titanium is slightly higher as compared to tungsten but less than graphite as the electrical resistivity and density of titanium is less than tungsten but higher than graphite. A concentration reaches an optimum level. The effect of pulse on duration and magnetic strength have not been found to be very significant and have been ranked as 5th and 6th respectively based on their F values. The MRR is found to increase on increasing the pulse on duration as more melting and vaporization of workpiece will take place when time for which the energy supplied increases. Magnetic strength has least effect on the MRR. The MRR obtained under the influence of magnetic field is slightly less than that obtained without the use of magnets but overall the effect of this factor is negligible. Optimal design In the experimental study, the mean effect plots is used to evaluate the mean MRR at optimal trial conditions considering higher F-value and corresponding percentage contribution two parameters are found to be significant tool material and current. The level of these factors which gives the maximum MRR are noted from main effect plot and the corresponding MRR for D_2,? E?_1 is directly obtained from Maximum value of these parameters is selected because MRR is the higher the better type of response variable. Desired mean in this case is estimated as: # Response table for MRR of EN-19 workpiece The workpiece samples from different views of H11 after each cut is shown in Figures shows top view The effect of powder mixed in dielectric, concentration of powder, current, tool material and pulse on duration on tool wear rate is analyzed with and without using external magnetic field on tool wear rate, using Taguchi experimental design. L18 orthogonal array is used for the experiments using bar magnets of 0.1 T. It is smaller the better type of response variable. TWR is calculated by measuring the initial and final weight of the tool using a weighing machine with least count of 0. # b) Results and analysis of TWR for EN-19 workpiece Based on this analysis conducted, most significant factor is tool material. The highest tool wear is observed with C18000 alloy followed by copper tool. Tungsten tool has been found to give the least tool wear. This is because of difference in the melting points of the tool materials. Thermal conductivity of copper at 100 ºC is about 400 W/m-K and of alloy C18000 is 208 W/m K and that of tungsten is 173 W/m-K although tool wear is found to decrease with increase in thermal conductivity but in this case it is not a dominating factor. Pulse on duration is the second factor affecting the tool wear rate after the tool material. The center line represents mean value of the levels. Main effect plots of TWR for EN-19 workpiece parameters is selected because TWR is the lower the better type of response variable. Desired mean in this case is estimated as: µ E 2 = ?? 2 + ?? 3 ? ?? = 0.000162 + 0.000555 -0.0010122 = -0.0002952 ? 0 The optimal calculation for population mean (µ) gives negative value. This situation may appear for responses which are lower the better type and where the optimum/target value is zero. For such case negative value of µ may not have any physical significance and is to be considered as zero. This experimental investigation was mainly aimed at comparing the tool wear behavior of the three tool material copper, C18000 and tungsten with and without using the external magnetic field. Different process parameters like current, pulse-on time, powder suspended in dielectric (tungsten, titanium and graphite) was varied at three levels with and without using magnetic field. Different output parameters measured are MRR, TWR, geometrical tool wear characteristics (corner wear, side wear), overcut. Some significant conclusions drawn on the basis of analysis of results ? Tool material is found to be the most significant factor in case of all the response variables measured with copper giving the highest MRR and TWR followed by C18000 alloy and tungsten. ? Besides tool material current is found to be the significant factor in affecting MRR for EN-19 workpiece materials, type of powder suspended in dielectric is found to affect the MRR for EN-19 workpiece materials. ? Including the tool material factor TWR is affected by pulse-on duration for EN-19 workpiece, by magnetic strength for EN-19 workpiece. ? EN-19 workpiece material is found to have maximum MRR and Graphite powder has reported better MRR compared to the two other powders used. ? Trials conducted in the presence of external magnetic field have reported to show better MRR and less TWR. ? Maximum MRR is achieved at the powder concentration of 2g/L. ? Maximum corner wear is reported in tool material C18000 alloy while maximum side wear is shown in tungsten tool. ? Overcut is found to decrease with increase in pulseon duration, presence of magnetic strength is also found to decrease the overcut. ? Maximum depth of cuts is achieved using copper as a tool material and using 4 A of current setting. ![a) Discharge VoltageDischarge voltage in EDM is related to the spark gap and breakdown strength of the dielectric.Before current flows, open gap voltage increases until it creates an ionization path through the dielectric. Once the current starts flowing, voltage drops and gets stabilized at the working gap level. Higher is the voltage, more is the gap, that improves the flushing conditions and helps to stabilize the cut. MRR, tool wear rate (TWR) and surface roughness increases, by increasing open circuit voltage, because electric field strength increases[Fuller, 1996].](image-2.png "") ![Journals Inc. (US) a) Objective of the present work g) Pulse-off Time](image-3.png "") ![Defining objective function ? Selecting an appropriate OA ? Selection of factors ? Pilot Experimentation ? Finalizing the factors and their levels a) Defining Objective Function](image-4.png "?") ![d) Calculation of DOF DOF denotes the number of the independent comparisons that can be made in any experiment. The number of factors considered for experimentation, their respective levels determine the total degree of freedom required for designing OA. Mathematically, DOF for each factor is calculated as, DOF= n-1, where n is the level of each factor e) Selection of OA for PMEDM Different factors considered for PEDM experiments and their levels are listed in](image-5.png "") ![which indicates the length of cut shows the side views where depth till which machining has been completed can be seen. Journals Inc. (US) µ D 2 ,E 1 = ?? 2 + ?? 1 ? ?? = 0.031552 + 0.040553 -0.0231456 = 0.0489594 g/min Confidence interval ???? = ? ?? ?? ,?? 1 ,?? 2 ?? ?? ?? ?????? Where ?? ??,? 1, ? 2 = F ratio ? = 0.1 (risk) Confidence = 1? ?? 1 = DOF for mean (always 1) ?? 2 = Total DOF (=17) ?? = Average of all experimental trials ?? ?????? = Number of tests under that condition using the participating factors ± 0.00966 Thus the optimum value of MRR is given by (0.0489594 ± 0.00966) g/min.](image-6.png "=") ![and Analysis of TWR](image-7.png "") 3Factors (unit)LevelsLevel 1Level 2Level 3Current (A)246Magnetic field0.1No-(T)Tool materialCopperC18000TungstenPowder typeTungstenCopperTitaniumConcentration246(g/L)Pulse-on time50100200(µs) Selection of workpieceS. NoParameterValue1Voltage135±5% V2PolarityPositive3Machining time8min4Pulse-off time57µs5DielectricEDM oilmediumEN-19 tool steel is very hard having the following Mechanical properties.Year 2015Mechanical properties of EN-19 steel Tensile strength 1150N/mm2Year 201530Yield stress850N/mm229III Version I e XV Issue ( ) Volum A Global Journal of Researches in EngineeringExp. No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18Elongation Modulus elasticity Density Magnetic strength Powder Concentration (g/L) With W 2 With W 4 With W 6 With Ti 2 With Ti 4 With Ti 6 With Gr 2 With Gr 4 With Gr 6 Without W 2 Without W 4 Without W 6 Without Ti 2 Without Ti 4 Without Ti 6 Without Gr 2 Without Gr 4 Without Gr 6 VI.14-17% 210000N/mm2 7.8Kg/m3 Current (A) Tool material Pulse-on of (µs) 2 Cu 50 4 W 100 6 C18000 200 2 W 100 4 C18000 200 6 Cu 50 4 Cu 200 6 W 50 2 C18000 100 6 C18000 100 2 Cu 200 4 W 50 4 C18000 50 6 Cu 100 2 W 200 6 W 200 2 C18000 50 4 Cu 100MRR (g/min) 0.05200 0.00533 0.01333 0.01200 0.02733 0.02000 0.06000 0.00800 0.01000 0.01733 0.02533 0.00666 0.03133 0.02733 0.01200 0.00533 0.02466 0.05866Journal of Researches in Engineering ( ) Volume XV Issue III Version I© 2015 Global Journals Inc. (US) ParameterSymbolDOFSSVariance F-value p-valuePCMagnetic strength (T)A10.000000.000000.00.9890PowderB20.0002010.0001010.910.4523.822Concentration (g/L)C20.0003830.0001921.730.2557.284Current (A)D20.0008020.0004013.630.09315.252Tool materialE20.0031920.00159614.440.00560.707Pulse-on time (µs)F20.0000170.0000080.080.9270.323Residual error Total6 170.000663 0.0052580.00011112.60Year 201531XV Issue III Version I( ) Volumeof Researches in EngineeringGlobal Journal© 20 15 Global Journals Inc. (US) © 20 15 Global Journals Inc. (US) Experimental Investigation Of Magnetic Field Assisted On Edm Process By using Taguchi Method On En-19Tool Steel t = Machining time (min) © 20 15 Global Journals Inc. (US) © 2015 Global Journals Inc. (US) ## Optimal Design In the experimental study, the mean effect plots. are used to evaluate the mean TWR at optimal trial conditions. From Table considering higher F-value and corresponding percentage contribution three parameters are found to be significant tool material followed by current and type of powder. The level of these factors which gives the minimum TWR are noted from main effect and the corresponding TWR for E_2 and F_3 is directly obtained. Minimum value of these * Anil and Paramjit singh, jully-sept. 2010some study of electric discharge machining of hastelloy using powder metallurgy electrode NaveenVijay Kumar Beri International journal of advanced engineering technology 0976-3945 * Mechanism of Material Deposition from Powder ,Electrode and Dielectric for Surface Modification of H11 and H13 die steels in EDM Process ABatish ABhattacharya Material Science Forum 701 2012 * Surface Modification of Carbon High Chromium ABhattacharya ABatish 2012 31