Experimental Study of MRR, TWR, SR on SS 316 and AISI D2 steel using Aluminium Electrode on EDM


Master's Thesis, 2016
68 Pages

Excerpt

Contents

Acknowledgement

Abstract

List of Figures

List of Tables

Abbreviations Used

Chapter 1- Introduction
1.1 Introduction and History of EDM
1.2 Working Principle
1.3 EDM Process
1.4 Advantages of EDM
1.5 Disadvantages of EDM
1.6 Dielectric Fluid
1.7 Electrode Material Selection
1.7.1 Electrical Conductivity
1.7.2 Melting Point
1.7.3 Structural Integrity
1.7.4 Mechanical Properties
1.7.5 Low Wear Rate
1.7.6 Metallic Electrodes
1.8 EDM Parameters
1.8.1 Pulse On Time
1.8.2 Pulse Off Time
1.8.3 Peak Current
1.8.4 Voltage

Chapter 2- Literature Review
2.1 Introduction
2.2 Literature Survey
2.3 Gap in Literature
2.4 Objective of Present Study

Chapter 3- Methodology
3.1 Phasing of Work
3.2 Experimental Setup
3.3 Workpiece and Electrode used for experimental work
3.3.1 Workpiece Material
3.3.2 Electrode Material
3.4 Machine used for experiments
3.5 Specifications of EDM
3.6 Machine used to measure weight
3.7 Machine used to measure surface roughness
3.8 Taguchi Method
3.8.1 Input Parameters
3.8.2 Response Variables
3.9 Evaluation of MRR
3.10 Evaluation of EWR

Chapter 4 Analysis and Results
4.1 Analysis and results of MRR of AISI D2 steel
4.1.1 Analysis and results of MRR for machined surface
4.1.2 Observation table for MRR
4.1.3 Analysis of Variance for MRR
4.1.4 Confirmation Test
4.1.5 Main effect plots
4.2 Analysis and result of TWR of AISI D2 steel
4.2.1 Results and analysis of TWR for machined surface
4.2.2 Observation Table for TWR
4.2.3 Analysis of Variance for TWR
4.2.4 Confirmation Test
4.2.5 Main effects plot
4.3 Analysis and results of SR of AISI D2 steel
4.3.1 Results and analysis of SR for machined surface
4.3.2 Observation Table for SR
4.3.3 Analysis of Variance
4.3.4 Confirmation Test
4.3.5 Main effects plot
4.4 Analysis and results of MRR of SS316
4.4.1 Analysis and results of MRR for machined surface
4.4.2 Observation table for MRR
4.4.3 Analysis of Variance for MRR
4.4.4 Confirmation Test
4.4.5 Main effect plots
4.5 Analysis and result of TWR of SS316
4.5.1 Results and analysis of TWR for machined surface
4.5.2 Observation Table for TWR
4.5.3 Analysis of Variance for TWR
4.5.4 Confirmation Test
4.5.5 Main effects plot
4.6 Analysis and results of SR of SS316 steel
4.6.1 Results and analysis of SR for machined surface
4.6.2 Observation Table for SR
4.6.3 Analysis of Variance
4.6.4 Confirmation Test
4.6.5 Main effects plot

Chapter 5 - Conclusion and Scope for future work

References

ACKNOWLEDGEMENTS

Dissertation work is an important aspect in the field of engineering. I express my sincere gratitude to Ambala College of Engineering and Applied Research, Ambala and Kurukshetra University, Kurukshetra for giving me the opportunity to work on the Dissertation during my final year of M.Tech.

I would like to thank my guide Dr. S.K. Jain, H.O.D, ME Department, and co-guide Er. Gurpinder Singh for their valuable support and to the members of Departmental Research Committee for their valuable suggestions and healthy criticism during dissertation work. I would like to thank Dr. J.K. Sharma and Er. Manpreet Singh for their valuable support. I would also like to thank everyone who has knowingly & unknowingly helped me throughout my Dissertation.

I am also thankful for the authors of all those books and papers which I had consulted during my Dissertation work as well as for preparing the report.

At the end, thanks to the Almighty for Everything.

ABSTRACT

In present study, the effect of aluminium tool electrode has been studied on stainless steel 316 and AISI D2 steel. Dielectric used for the study was EDM oil. Experiments were conducted based on L9 orthogonal array. The experimental study on the effect of input parameters i.e. current, pulse on time and pulse off time on output parameters material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR). The workpiece materials selected were AISI D2 steel andß316. The tool electrode used was Aluminium and EDM oil as dielectric fluid. Taguchi design of experiments was used to design experiments, L9 orthogonal array was applied using MINITAB software. Signal to noise ratio and ANOVA were employed for parameter optimization and to achieve max MRR, min TWR and SR. The results indicate that the most influencing factor for MRR is Pulse off time. For TWR, the most influencing factor is current. For SR, the most influencing factor is pulse on time.

List of Figures

1.1 Schematics of EDM process

1.2 (a) Occurrence of spark at the closest point b/w Work piece and electrode
(b) Melting and vaporization of workpiece and Electrode during spark on time
(c) Vaporized cloud of materials suspended in 4 Dielectric fluid
(d) Removal of molten metal and occurrence of 4 Next spark

1.3 EDM process

3.1 Procedure of research work

3.2 Workpiece before machining, SS316

3.3 Workpiece after machining, SS316

3.4 Workpiece before machining, AISI D2

3.5 Workpiece after machining, AISI D2

3.6 Aluminium electrode used for experiments

3.7 Surface roughness tester

4.1 Main effects plot for SN ratio for MRR of AISI D2 steel

4.2 Main effects plot for Means for MRR of AISI D2 steel

4.3 Main effects plot for SN ratio for TWR of AISI D2 steel

4.4 Main effects plot for Means for TWR of AISI D2 steel

4.5 Main effects plot for SN ratio for SR of AISI D2 steel

4.6 Main effects plot for Means for SR of AISI D2 steel

4.7 Main effects plot for SN ratio for MRR of SS316

4.8 Main effects plot for Means for MRR of SS316

4.9 Main effects plot for SN ratio for TWR of SS316

4.10 Main effects plot for Means for TWR of SS316

4.11 Main effects plot for SN ratio for SR of SS316

4.12 Main effects plot for Means for SR of SS316

List of Tables

3.1ß316 Composition

3.2 AISI D2 steel Composition

3.3 Properties of Aluminium

3.4 EDM Specifications

3.5 SRT 6210 specifications

3.6 Input parameters and their levels

4.1 Observation table for MRR of AISI D2 steel

4.2 Response Table for S/N ratio for MRR of AISI D2 steel

4.3 Response table for means for MRR of AISI D2 steel

4.4 ANOVA table for S/N Ratio

4.5 ANOVA table for Means

4.6 Observation table for TWR of AISI D2 steel

4.7 Response table for S/N ratio for TWR of AISI D2 steel

4.8 Response Table for means for TWR of AISI D2 steel

4.9 ANOVA table for S/N Ratio

4.10 ANOVA table for Means

4.11 Observation table for SR of AISI D2 steel

4.12 Response Table for S/N ratio for SR of AISI D2 steel

4.13 Response table for means for SR of AISI D2 steel

4.14 ANOVA table for S/N Ratio

4.15 ANOVA table for Means

4.16 Observation Table for MRR ofß316

4.17 Response Table for S/N ratio for MRR ofß316

4.18 Response table for Means for MRR ofß316

4.19 ANOVA table for S/N Ratio

4.20 ANOVA table for Means

4.21 Observation Table for TWR ofß316

4.22 Response table for S/N ratio for TWR ofß316

4.23 Response table for Means for TWR ofß316

4.24 ANOVA table for S/N Ratio

4.25 ANOVA table for Means

4.26 Observation table for SR ofß316

4.27 Response table for S/N ratio for SR ofß316

4.28 Response table for Means for SR of SS316

4.29 ANOVA table for S/N Ratio

4.30 ANOVA table for Means

Abbreviations Used

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Chapter 1 - Introduction

1.1 Introduction and History of EDM:

When sparking takes place between two electrically conductive materials which are placed very close to each other, a small amount of material is removed from each of the material. It was first discovered by Joseph Priestly in 1770s. The Electric discharge machining started developing in mid 1970s. In mid 1980s, the EDM techniques were transferred to a machine tool. Today, it is the viable technique in the metal cutting industry with a wide number of applications and advantages.

The metal removal due to sparking was realized and attempts were made to harness and control the spark energy to employ it for useful purpose that is machining of metals. It was found that the spark of short duration and high frequency are needed for efficient machining. Further, it was also observed that if we submerge the discharge in dielectric, we can concentrate energy onto a small area.

A relaxation circuit that is RC circuit was proposed in which tool and workpiece i.e. electrodes are immersed into the dielectric like kerosene, and are connected to a capacitor. The capacitor is charged from a direct current source. Fig. 1.1 shows the RC circuit. As soon as the potential across the tool and the workpiece crosses the breakdown voltage, the sparking takes place at a point of least electrical resistance, which is usually the smallest inter-electrode gap (IEG). After every successive discharge capacitor recharges and spark will takes place at the next narrowest gap. Whenever a spark occurs heat is generated, which is shared in different modes by workpiece, tool, dielectric, debris and other parts of the system.

The dielectric serves some important functions like cools down the tool and workpiece, cleans the IEG, and concentrating the spark energy on a small cross sectional area.

EDM spark erosion is the same as having an electrical short that burns a small hole in a piece of metal it contacts. For a successful EDM process both the workpiece and tool must be electrically conductive.

The EDM process can be used in two different ways:

1. A pre-shaped electrode or tool usually made from copper or graphite or other conductive material is shaped in the same shape of the cavity required on the workpiece.

This tool is fed vertically down and the reverse shape of the tool is eroded into the solid workpiece.

2. A continuous travelling vertical wire electrode, the dia. of a small needle or less, is controlled by the computer to follow a path which is programmed to erode or to cut a slot or a narrow slot through the workpiece to produce the required shape

One of the most important factor in EDM operation is the removal of the metal particles that is chips from the working gap. This is known as flushing. Flushing these particles out of the gap between the workpiece to prevent them from forming bridges that cause short circuits.

Electric Discharge Machining is classified as Non-conventional machining process because the tool and the workpiece are not in direct contact, for the purpose of material removal.

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Fig 1.1 Schematics of EDM process

1.2 Working principle of EDM

Electric discharge machining (EDM) is a controlled metal removal process which is used to remove metals by electric spark erosion. In this process, electric spark is utilized as the cutting tool to cut the workpiece to produce the finished part of the desired shape. The metal removal process is carried out by applying a pulsating on/off electrical charge of high frequency current through the electrode of the workpiece. This removes very tiny pieces of metal from the workpiece at a controlled rate.

EDM is a thermo-electric process because heat energy of a spark is used to remove material from the workpiece. The workpiece and the tool should me electrically conductive materials. A spark is produced between the tool and the workpiece and the location of spark is determined by the narrowest gap between the two. Each spark is of very short duration. The time of the entire cycle is very few micro-seconds (μs). The frequency of the sparking may be as high as thousands of sparks per second. The spark is effective on a very small area. But the temperature of the spark area is very high. So the spark energy is capable of partly melting and partly vaporizing the material from the localized area of both tool and the workpiece.

The cavity produced on the workpiece is approximately the replica of the tool. But in order to achieve the exact replica of the tool, the tool wear must be zero. So to minimize the tool wear the operating parameters and polarity should be selected carefully. Particles eroded from the surface of electrodes are known as debris. Analysis of debris has revealed that it is a mixture of irregular shaped particles as well as hollow shaped particles.

A very small gap (of the order of hundredth of millimeter or even smaller) between the two electrodes is maintained in order to have a spark to occur. During EDM, pulsed DC of 80-100 V is passed through the electrodes. It results in the intense electrical field at the location where surface irregularity provides the smallest gap. Electrons break loose from the cathode surface and move towards the anode under the influence of electric field forces.

During this, the electrons collides with the neutral molecules of the dielectric and due to this electrons are also detached from these neutral molecules of the dielectric resulting in still more ionization. The ionization becomes so intense that a very narrow channel of continuous conductivity is established. In this continuous flow, considerable amount of electrons moves towards anode and that of ions moves towards cathode. Their kinetic energy is converted into heat energy hence heating of anode takes place due to bombardment of electrons and heating of cathode takes place due to bombardment of ions.

Thus it ends up in a momentary current impulse resulting in a discharge which is a spark. The spark energy raises the localized temperature of the electrodes to such a high value that it results in the melting, or melting as well as vaporization of material from the surface of both electrodes at the point of spark contact takes place in a very small amount.

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Figure No. 1.2(a) Occurrence of spark at the closest point between work piece and electrode, 1.2(b) melting and vaporization of work piece and electrode materials during spark on-time, 1.2(c) Vaporized cloud of materials suspended in dielectric fluid, and 1.2(d) Removal of molten metal and occurrence of next spark.

In fact, dielectric gets evaporated and the pressure in the plasma channel rises to a very high value and it does not let the evaporation of superheated metal. As soon as the off time of a pulse starts, the pressure drops instantaneously which allows the evaporation of superheated metal. The amount of material eroded from the workpiece and the tool will depend upon the contributions of K.E. of electrons and ions respectively. The polarity normally used is straight in which tool is negative and workpiece is positive while in reverse polarity vice versa. Movement of tool towards the workpiece is controlled by a servo mechanism. The sparking takes place over the entire surface of the workpiece hence the replica of the tool is produced. Usually a component made by EDM process is machined in two stages:

1. Rough machining at high MRR with poor surface finish,
2. Finish machining at low MRR with high surface finish.

1.3 EDM process

Among the thermal modes of machining, electrical discharge machining is mainly a technique used for the manufacture of a multitude of ever changing geometries very often produced as unit jobs or in small batches. After the pioneering investigations of Larezenko, the EDM process has attracted worldwide attention as a technique for metal machining and since then considerable research and development have been carried out.

The basic concepts of EDM process is crating out of metals affected by the sudden stoppage of the electron beam by the solid metal surface of anode. The portion of the anode facing the direct electrical pulse reaches the boiling point. Even in the case of medium long pulse the rate of temperature increase in tens of millions of degree per second which means dealing with an explosion process. The shock wave produced spreads from the center of the explosion to the inside the metal and on its way crushes the metal and deform crystal structure. In a very small duration of process the entire energy can only be expended in the surface layer of the anode. In reality, the mechanism of thermal conductivity has no time to start before the violet process of energy transfer is completed.

When a suitable unipolar (pulsed) voltage is applied across two electrodes by a dielectric fluid the latter breaks down. The electrons so liberated, are accelerated in presence of the electric field collide with the dielectric molecules, causing them to be robbed off their one or two electrons each and immunize.

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Fig 1.3 EDM process

The process grows and multiplies with secondary emission followed by an avalanche of electrons and ions. Dielectric layer’s resistance drops as it is ionized resulting into ultimate breakdown. The electric energy is concentrated onto the gap and multifarious action takes place. Electro dynamic waves set in and travel at high speed high speed causing shock-impact and high temperature rise at the electrode surfaces. The instantaneous temperature may reach as high as 10,000 0 C causing localized vaporization of the electrodes.

1.4 Advantages of EDM

To machine some of the hardest materials, EDM process has following important advantages which make it widely used in practice:

1. The process can be applied, in general, to any electrically conductive material. Other properties like strength, brittleness, etc. do not impose any restrictions to the application of the process.
2. The process provides a simple and straightforward method of form producing drop- forging, drawing and extruding dies and complex cavities in moulds and dies for plastics, die casting, glass and ceramic manufacturing.
3. Though the process involves temperature rise at the local spots to about 10,000 0 C which can vaporize the localized material to machine, there is no heating of the bulk materials. However, the ‘heat affected zone’ (HAZ) surrounding the local points extends in the bulk to a depth of about few microns.
4. The high rates of heating and cooling at the treated surface renders some extra hardness (case-hardening) to the surface and this becomes a point of advantage in favour of the process.
5. Simple geometrical shape configurations can easily be produced by piercing or die- sinking in hardened die plates with required accuracy and surface finish. Thus, elimination of much complicated grinding and lapping is possible.
6. No mechanical stress is developed in the work material as there in no physical contact between the tool and work piece. This permits machining fragile and slender work pieces.
7. The process reduces time of machining in comparison with conventional grinding, honing or contour grinding etc.
8. The crater type non-directional (layless) surface pattern is said to retain lubricants, rendering the process particularly suitable for the finishing operation.
9. The surface finish produced by EDM process can be controlled to the required extent, minimizing the extra cost involved in additional operation for achieving improved surface finish.
10. Complex shapes which are difficult to produce with conventional machining methods can be produced on EDM
11. Extremely hard metals can be machined on EDM,
12. Very small work pieces which may get damaged from conventional cutting tool can be machined on EDM safely.
13. No direct contact between tool and the work pieces hence no mechanical stresses therefore delicate and weak materials can be machined without distortion.
14. Good surface finish can be achieved.

1.5 Disadvantages

1. The machining rate is very slow.
2. Potential fire hazard due to use of inflammable dielectrics use.
3. Very high power consumption.
4. Electrically non-conductive materials cannot be machined.
5. Overcut is formed.
6. Not capable to produce extreme sharp corners.
7. Size of the work piece is a constraint and depends on the machine set up. But generally large workpieces cannot be machined.

1.6 Dielectric Fluid

Since the process of removal of materials (both from work and tool) mainly depends upon thermal evaporation and melting, the presence of oxygen in atmosphere surrounding the spark would lead to formation of metal oxides which adversely affect the continuation or generation of repetitive sparks (most of metal oxides are bad conductor). Hence it is pertinent to use a dielectric fluid which contains no oxygen for liberation during the process, to help ionization, without disturbing the process.

But the performance of the dielectric to suit the purpose is extremely important. The failure of dielectric under electric stress, termed as breakdown, is found to spread over a wide range of applied stresses, depending upon its environment and mode of use.

1.7 Electrode material selection

1.7.1 Electrical Conductivity

The cutting tool in EDM is electric current, higher conductivity (or conversely, lower resistivity) promotes more efficient cutting.

1.7.2 Melting Point

We know that EDM is a thermal process, so we can assume that the higher the melting point of the electrode material, the better will be the wear ratio between electrode and workpiece.

1.7.3 Structural Integrity

EDM is thought of as a zero force process often, each individual spark is a very violent process on a microscopic scale, which exerts a considerable stress on the electrode material. How well the material surface will respond to these attacks, so it shall be an important factor in determining the electrode material’s performance.

1.7.4 Mechanical Properties

The mechanical properties for electrode materials are:

1. Tensile strength
2. Transverse Rupture Strength (if applicable)
3. Grain Size (if applicable)
4. Hardness

1.7.5 Low Wear Burns

Electrode wear is a function of power supply settings, but is also of electrode properties. The combination of Electrode-workpiece pairs, polarity, Peak current and pulse on time, material lost from the electrode surface is re-plated back onto the electrode surface.

It should be noted that the re-deposited material is a combination of dielectric, workpiece and electrode.

Low wear rate is associated with electrode with positive polarity and long pulse on-time. Under extreme conditions, it is possible to actually grow the electrode rather than wear only. It is not a desirable condition.

1.7.6 Metallic Electrodes

The advantage of using metallic electrode is their electrical conductivity and mechanical integrity.

The disadvantages of using metallic electrodes are difficulty in fabrication and low cutting speeds.

1.8 EDM parameters

1.8.1 Pulse on time

Time during which machining takes place is called as pulse on time. Machining rate can be increased by increasing pulse on time and at the same time surface roughness also increases.

1.8.2 Pulse off time

Time during which reionization of the dielectric takes place is the pulse off time. Sufficient off time must be allowed before starting a new cycle. The shorter the pulse off time, faster will be the machining. But if pulse off time is kept too short then material removed from workpiece will not be swept away by the dielectric and dielectric will not deionize. This will cause the next spark to be unstable.

1.8.3 Peak Current

This is the most important parameter of the EDM, measured in amperes. As current increases material removal rate increases and current also affects electrode wear rate and surface finish. Higher the current, higher will be the tool wear rate and poor will be the surface finish. During the pulse-on time the current increases it reaches to level that is called peak current.

1.8.4 Voltage

It is potential that can be measured by volt. It affects material removal rate. Voltage is generally kept constant during experimentation. But it can be varied to study effects of voltage change on selected parameter.

Chapter 2 - Literature Review

2.1 Introduction

A lot of work has been done on different aspects of EDM. The EDM process has a wide application in die making industry and it also one of the best and most studied non-conventional machining technique. This chapter will cover the literature review of input parameters like Current, Pulse on time, Pulse off time, dielectric, and electrode on output parameters like Material removal rate, tool wear rate and surface roughness of the machined material. It is also a well suited method to machine hard to machined materials by conventional methods. Many parameters effect the quality of the machined material and hence many researchers had done work and gave their findings, a brief of which is given below.

2.2 Literature Survey

Lee and Li (2001) stated that for machining of tungsten carbide, graphite electrode gives the highest MRR with comparison to copper and copper tungsten electrode. For lower current values the wear ratio decreases for graphite but increases for copper. They exhibit copper tungsten exhibit lowest wear ratio at all ranges of peak current. They also observed the reverse polarity gives higher MRR, lower relative wear and better surface finish. They found optimal dielectric flushing pressure is 50Kpa. For precision machining of tungsten carbide, the optimum conditions of relative wear ratio and surface roughness achieved at a gap voltage of 120 V, discharge current 24A, pulse duration of 12.8 μs. [21]

Ho and Newman (2003) researched EDM relating to improving performance measures, optimizing the process variables. And monitor and control the sparking process. They suggested trend for future EDM research. [11]

Kristian (2004) states that EDM may be the only method available when manufacturing deep slots in low machinability materials. Their research concerns seal slots in Ni-Based turbine vanes. EDM Performance in respect to MRR and electrode wear is compared for 2 graphite qualities. They mentioned that based on the results the best choice of graphite quality grade for this app would be poco EDM3. If electrode wear also is important, very good conditions can be reached by some increase of pulse duration from 20 to 30 μs with a reduction of 6% MRR. [18]

Lauwers et al. (2004) have studied the material removal mechanisms for three composite ceramic materials, ZrO2 based, Si3N4 based, Al2O3 with additions of electrical conductive phases like Tin and TiCN. The spalling effect is proven to be related with the formation of cracks. The formation of cracks depends on other factors like thermal conductivity of material, melting point & strength on the fracture toughness of material. [19]

Abbas et al. (2007) reviewed the research trends in EDM on ultrasonic EDM, dry EDM machining, EDM with powder additives, water EDM. They stated that ultrasonic vibration method is suitable for micro machining, dry machining is cost effective and EDM in water is introduced for safe and conductive working environment, EDM with powder additives is concerned more on improving surface quality. [1]

Khanra et al. (2007) stated that the low wear resistance of Cu, Cu alloys and graphite is a major problem. They developed a composite ZrB2-Cu to get an optimum combination of wear resistance, electrical and thermal conductivity. This composite is used to machine mild steel. The ZrB2 40% wt. Cu composite shows more MRR with less TWR than copper tool. But the diametral overcut and average surface roughness is found to be less in case of Copper tool than composite. [17]

Haron et al. (2008) observed the performance of copper and graphite tool electrode with XW42 tool steel. They observed material removal rate by copper and graphite electrodes of 10, 15, 20 mm dia. By varying current and machining time one by one. MRR of XW42 tool steel with copper is greater than with graphite electrode. Copper is suitable for roughing process, while graphite electrode is suitable for finishing. They concluded that MRR not only depends upon the dia. Of electrode and supply of current but also on the type of electrode material used. [9]

Amin et al. (2009) discussed the feasibility of machining Tungsten carbide ceramics with a graphite electrode on EDM using Taguchi method. Taguchi method has been used to determine the optimum machining conditions for the performance of EDM. They concluded that, the peak current affects the electrode wear rate and surface roughness largely. The pulse duration mainly affects the MRR. By using ANOVA table they have found that peak current is most significant factor for EWR and SR. [2]

Sameh (2009) developed a comprehensive mathematical model for correlating the various EDM parameters and their influence through response surface methodology. They selected conductive metal matrix composite Al/Si as workpiece. Copper is used as electrode. They concluded that with increases in pulse on time cause as increase in MRR until it reaches 200 μs & then it began to decrease. EWR decreases as pulse on time increases for a combination of gap voltage and peak current. As MRR decreases, EWR also decreases. The surface roughness of the machined surface increases as the energy as the pulse energy increases. It means, MRR increases at a high pulse energy and hence surface will be rough. [31]

Jegan et al. (2012) investigated the EDM parameters using gray rational analysis on AISI 202 stainless steel, parameters mainly discharge current, and pulse on time and pulse off time and optimization of these parameters are done by GRA. The purpose of this experimental work is to know the effect of machining parameters and conclude these effects on MRR and SR. EDM oil is used as dielectric and workpiece AISI202 and copper as electrode. Their results shows that the main parameter that effect MRR is discharge current, so by properly adjusting the control factors, quality of product can be improved. [14]

Gopalakannan et al. (2012) carried out an experimental investigation to study the effect of pulsed current on MRR, EWR and SR and diametral overcut inß316L and 17-4 PH, electrodes used were copper, copper tungsten, graphite. It is observed that output parameters such as MRR, EWR and SR increases with increase in pulsed current. High MRR achieved with copper electrode whereas copper tungsten yielding lower EWR, smooth SF and good dimensional accuracy. [7]

Hindus et al. (2013) investigated the machining characteristics ofß316L through EDM. Copper is used as electrode. Results indicate that MRR and TWR is strongly influenced by current and pulse on time. Most significant factor for MRR found to be pulse on time followed by current. For TWR the most significant factor was current followed by pulse on time. [10]

Murikan et al. (2013) investigated environmental friendly dry EDM. Liquid dielectric is replaced by gaseous dielectrics. Investigation is done on stainless steel 316L using compressed air as dielectric and copper electrode as tool. The influence of discharge current, pulse on time, duty factor and spindle speed on MRR and TWR has been studied. From the results it is observed that maximum MRR of 9.94 mm3/min is obtained and is influenced by discharge current, pulse on time and duty factor. Minimum tool wear of 0.048 mm3/min is obtained and tool wear is influenced by discharge current and duty factor. [24]

Patel et al. (2013) performed experiments to determine parameters effecting surface roughness. Experiments were using copper, brass and aluminium as tool electrodes on Mild steel and kerosene oils as dielectric. MRR obtained: copper; 1.45 gm (10μs, 23.48 A), brass; 0.7 gm (200 μs, 23.48 A) and aluminium; 1.48 gm (20 μs, 23.48 A). SR increased with increase in current. SR of aluminium is more than copper followed by brass. [27]

Choudhary et al. (2013) investigated the effect of different electrodes on MRR, SR ofß316. Electrode material, current and pulse on time were taken as variables for the study of MRR and SR. Copper, brass and graphite were used as electrodes and EDM oil as dielectric. They concluded for MRR, electrode material is the most influencing factor and then discharge current. MRR increases with increase in current. Copper electrode shows highest MRR while Brass showed less. SR is better with lower value of current. Brass shows the better surface finish while copper shows the worst surface finish. [3]

Rahi et al. (2014) parametric analysis is conducted on High carbon high chromium steel with copper and graphite as electrodes and high carbon oil as dielectric. The effect of input parameters on MRR, EWR, SR has been studied. For MRR with copper electrode input current and duty cycle is more dominant. Pulse on time and duty cycle for EWR, duty cycle and pressure for surface roughness. [28]

Rajendra M. et al. (2014) investigated the effect of abrasive mixed dielectric on High carbon high chromium steel D3. Abrasive material used was Al2O3. Results indicates that abrasive particle size and concentration and pulse current are the most significant parameters that improves MRR. By adding abrasive particle, efficiency of EDM increases. As per S/N ratio and ANOVA, MRR is influenced by discharge current and abrasive concentration. At 6 g/ltr of concentration MRR is maximum. Abrasive mixed EDM results in 58% more MRR than the traditional EDM. [29]

Laxman and Guru Raj (2014) optimized the EDM parameters using gray relational analysis. Effect of parameters peak current, pulse on time, and pulse off time on MRR and TWR is studied. Taguchi design of experiments is used. Dielectric used was EDM oil grade 30. Copper electrode is used for experimentation. Experimental investigation has been carried out on titanium super alloys. The results of ANOVA indicates that pulse current is the most influencing factor for machining of titanium super alloy. [20]

Raju et al. (2014) investigated the effect of surface roughness of the most influenced parameters pulse on time, peak current, servo voltage and wire tension onß316L. Signal to noise ratio is used to find the optimal combination of parameters. Assumptions of ANOVA were verified and found to be valid. It is found that the machining variable pulse on time is the significant factor that effect surface roughness. [30]

Suresh et al. (2014) conducted investigation of MRR of SS316L. Input parameters selected are current, pulse on time and pulse off time. Tungsten electrode was used of 300 μm diameter. The S/N ratio on MRR reveals that the current plays the most significant role in the parameters chosen thus the developed mathematical model is well suited to improve the productivity for selecting the optimal parameters. [36]

Dixit et al. (2015) investigated the parameters MRR, EWR on AISI D3 steel. Input parameters are pulse on time, pulse off time, peak current and fluid pressure. Copper electrode is used to perform the experiment and analyzed using Taguchi method. It is concluded that MRR is mainly influenced by peak current and EWR is mainly influenced by peak current followed by pulse on time. [6]

2.3 Gap in Literature

From literature survey it is seen that a lot of work has been done on different aspects of EDM. Many researchers worked on EDM parameters like current, pulse on time, pulse off time, electrode material and dielectric fluid and studied the effect of these parameters on material removal rate, tool wear rate and surface roughness. Many researchers have used different electrodes like copper, brass and graphite. Few have used tungsten and tungsten carbide. But copper and graphite being the most commonly used due to the fact that conductive properties are good. Very few researchers have used aluminium as electrode. Aluminium also has very good conductive properties. As we can see in literature review, materials used for research purpose areß316, mild steel, AISI 202, titanium alloys and AISI D2 and D3 steel.ß316 has wide number of applications because of its very high corrosion resistance. Now a days it is used in orthopedic implants and also in Food preparation equipment particularly in chloride environments, pharmaceuticals piping.ß316 is hard to machine material with conventional machining processes. So EDM is a suitable method.

[...]

Excerpt out of 68 pages

Details

Title
Experimental Study of MRR, TWR, SR on SS 316 and AISI D2 steel using Aluminium Electrode on EDM
Course
Master of Technology, Manufacturing Systems
Author
Year
2016
Pages
68
Catalog Number
V342374
ISBN (eBook)
9783668388086
ISBN (Book)
9783668388093
File size
1431 KB
Language
English
Tags
EDM, SS 316, AISI D2, Aluminium Electrode, Minitab 17, ANOVA, MRR, TWR, SR
Quote paper
Sidhant Gupta (Author), 2016, Experimental Study of MRR, TWR, SR on SS 316 and AISI D2 steel using Aluminium Electrode on EDM, Munich, GRIN Verlag, https://www.grin.com/document/342374

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Title: Experimental Study of MRR, TWR, SR on SS 316 and AISI D2 steel using Aluminium Electrode on EDM


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