Project on EDM

Characterization of Metals Machined

Using EDM

MAJOR PROJECT

SUBMITTED IN PARTIAL FULFILLMENT OF REQUIREMENTS FOR THE AWARD OF

THE DEGREE OF

BACHELOR OF TECHNOLOGY

MECHANICAL ENGINEERING

BY

SAHIL GARG VINEET (12001004055) (12001004063)

RAJU RAMPHAL (12001004047) (12001004048)

UNDER THE GUIDANCE OF

Dr. M.N MISHRA

DEPARTMENT OF MECHANICAL ENGINEERING

FACULTY OF ENGINEERING & TECHNOLOGY

D.C.R. UNIVERSITY OF SCIENCE & TECHNOLOGY

MURTHAL, SONEPAT, HARYANA (INDIA) – 131 039

(April 2016)

i

CONTENTS

Page No.

Declaration by the candidates ii

Abstract iii

Acknowledgement iv

List of Figures and Tables v

List of Graphs vi

Chapter 1: INTRODUCTION 1-2

1.1 Introduction

1.2 Motivation for the selection of project

1.3 Objectives of Project Work

Chapter 2: Literature Review 3-11

2.1 Spark Erosion Machining Process

2.2. Spark Erosion Generators

2.2.1 Lift

2.2.2 Electrode Feed Control

2.3 EDM Sequence

2.4 Advantages of using EDM as the machining process

2.5 Gap Sense

Chapter 3: Concept and Theory of the problem 12-15

3.1 Apparatus i.e. EDM SN125

3.2. Material used

3.3 Design of Experiment

3.3.1 Parameters varies on EDM

3.3.2 Parameters to be studied

3.3.3 Methodology of Experiment .

Chapter 4: Performance Analysis 16-31

4.1 Experimental Data

4.1.1 S30400

4.1.2 D2

4.2 Study of Properties

4.2.1 Effect of parameters on MRR

4.2.2 Effect of parameters on Grain Size

4.2.3 Effect of parameters on Hardness

4.2.4 Effect of parameters on Roughness

Chapter 5: Results and Discussions 32-33

5.1 Optimal set of parameters for SS304

5.2 Optimal set of parameters for D2

References 34

Appendix 35-46

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DECLARATION BY THE CANDIDATES

We hereby certify that the work which is being presented in this Project report entitled

‘CHARACTERIZATION OF METALS MACHINED USING EDM’ in partial fulfillment of

requirements for the award of degree of BACHELOR OF TECHNOLOGY in MECHANICAL

ENGINEERING, submitted to the Dept. of Mechanical Engineering, Faculty of Engineering &

Technology, Deenbandhu Chhotu Ram University of Science & Technology, Murthal,

Sonepat (Haryana) is an authentic record of our own work carried out during a period from

August 2015 to May 2016 under the supervision of Dr. M.N Mishra. The matter presented in

this project work has not been submitted to any other University / Institute for the award of

B.Tech or any other Degree / Diploma.

Name (Roll. No.) Signature

1. SAHIL GARG

(12001004055)

2. VINEET

(12001004063)

3. RAJU

(12001004047)

4. RAMPHAL

(12001004048)

This is to certify that the above statement made by the candidate is correct to the best of my

knowledge & belief.

Signature of Supervisor

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Abstract

Spark erosion machining is a process based on the disintegration of the dielectric and the current

conduction between the job and the work piece by an electric discharge occurring between them. This

process is also called as Electro Discharge Machining/Electro Erosion Process/Electro Spark

Machining. In this method job and the work piece (which act as electrodes) are separated by a certain

gap filled with a dielectric medium. A preset pulse across the work piece and job. Depending upon the

micro irregularities of tool and work piece surfaces and presence of carbon and metal particles, the

dielectric is broken down at several points producing ionized columns which allow a focused stream

of electrons to flow and produces compression shock waves and there is an intense increase in local

temperatures. Due to combined effect of these two particles of metal are thrown out very much similar

to the boiling out of water. As erosion progresses the gap changes and that gap is continuously

maintained by the servomechanism.

This process incorporates two unique features viz.

1. Absence of any cutting force between tool and work piece.

2. Absence of any effect of hardness of work piece on cutting action. These features allow this

process to be used in producing fine slots or micro drills in thin delicate parts like electrical

and electronic equipment’s. The spark erosion process is effective in machining electrically

conductive but extremely brittle material. In machining super hard material like cemented

carbide, in removing broken drills, taps etc.

Besides being unique in above applications this process can replace the

conventional extra laborious die cavity producing methods. Since the shape

of the cavity being eroded corresponds to the shape of tool, this process is

very convenient and economical for various die sinking applications.

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ACKNOWLEDGEMENT

We are highly grateful to the Hon’ble Vice-Chancellor, D.C.R. Univ. of Science &

Technology, Murthal, Sonepat for providing us this opportunity to carry out the present

project work.

The constant guidance and encouragement received from Dr. Rajender Bhardwaj ,

Prof. & Chairperson, Dept. of Mechanical Engineering, Deenbandhu Chhotu Ram University

of Science & Technology, Murthal, Sonepat has been of great help in carrying out the

present work and is acknowledged with reverential thanks.

We would like to express a deep sense of gratitude and thanks profusely to our

Project Supervisor, Dr. M.N Mishra, Professor, Dept. of Mechanical Engineering,

Deenbandhu Chhotu Ram University of Science & Technology, Murthal, Sonepat .Without

his able guidance, it would have been impossible to complete the project in this manner.

The help rendered by Dr. M.S Narwal , B.Tech. Project Coordinator, Department of

Mechanical Engineering, Deenbandhu Chhotu Ram University of Science & Technology,

Murthal, Sonepat for his wise counsel is greatly acknowledged. We also express our

gratitude to other faculty members of Dept. of Mechanical Engineering, Deenbandhu Chhotu

Ram University of Science & Technology, Murthal, Sonepat for their intellectual support

throughout the course of this work.

The copious help received from Sh. M.R Saini, Sh. Kamal and Sh. Hamender , the

Technician Staff of the Dept. of Mechanical Engineering, D.C.R. Univ. of Science &

Technology, Murthal, Sonepat for the excellent Laboratory support is also acknowledged.

Finally, We are indebted to all whosoever have contributed in this project work.

Name (Roll. No.) Signature

1. SAHIL GARG

(12001004055)

2. VINEET

(12001004063)

3. RAJU

(12001004047)

4. RAMPHAL

(12001004048)

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List of Figures and Tables

Fig 2.1 Schematic representation of the basic working principle of EDM

process

Fig 2.2 Elementary relaxation circuit for EDM

Fig. 2.3 Waveform used in EDM

Fig. 2.4 Electrode Feed Control in EDM

Fig. 4.1 S30400 machined surface 1

Table 4.1 Testing on S30400 surface 1


Table 4.3.1 Testing on D2


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List of Graphs

Graph 4.1 S/N ratios for MRR v/s Ampere for S304 with Lift 0.2mm


Graph 4.3 S/N ratios for MRR v/s Ampere for D2 with Lift 0.2mm


Graph 4.5 Grain Size v/s Current for S304 with Lift 0.2mm


Graph 4.7 Grain Size v/s Current for D2 with Lift 0.2mm


Graph 4.9 Hardness v/s Current for S304 with Lift 0.2mm


Graph 4.11 Hardness v/s Current for D2 with Lift 0.2mm


Graph 4.13 S/N ratio for Roughness v/s Current for S304


Graph 4.15 S/N ratio for Roughness v/s Current for D2 with Lift 0.2mm

Graph 4.16 S/N ratio for Roughness v/s Current for D2 Lift 0.4mm

1

Chapter – 1

Introduction

1.1 Introduction

Electro Discharge Machining (EDM) is an electro-thermal non-traditional machining

process, where electrical energy is used to generate electrical spark and material removal

mainly occurs due to thermal energy of the spark.

EDM is mainly used to machine difficult- to-machine materials and high strength

temperature resistant alloys. EDM can be used to machine difficult geometries in small

batches or even on job-shop basis. Work material to be machined by EDM has to be

electrically conductive. [1]

1.2 Motivation for the selection of Project

The history of EDM Machining Techniques goes as far back as 1770, when English chemist

Joseph Priestly discovered the erosive effect of electrical discharges or sparks. The EDM

process was invented by two Russian scientists, Dr. B.R. Lazarenko and Dr. N.I. Lazarenko

in 1943. The spark generator used in 1943, known as the Lazarenko circuit, has been

employed over many years in power supplies for EDM machines and proved to be used in

many current applications. The Lazarenko EDM system uses resistance- capacitance type of

power supply, which was widely used at the EDM machine in the 1950's and later served as

the model for successive development in EDM. Further developments in the 1960's of pulse

and solid state generators reduced previous problems with weak electrode as well as the

inventions of orbiting systems. In the 1970's the number of electrodes is reduced to create

cavities. Finally, in the 1980's a computer numerical controlled (CNC) EDM was introduced

in USA. The new concept of manufacturing uses non-conventional energy sources like sound, light,

mechanical, chemical, electrical, electrons and ions. With the industrial and technological

growth, development of harder and difficult to machine materials, which find wide

application in aerospace, nuclear engineering and other industries owing to their high strength

to weight ratio, hardness and heat resistance qualities has been witnessed. New developments

in the field of material science have led to new engineering metallic materials, composite

materials and high tech ceramics having good mechanical properties and thermal

characteristics as well as sufficient electrical conductivity so that they can readily be

machined by spark erosion. Non-traditional machining has grown out of the need to machine

these exotic materials.[2]

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1.3 Objectives of Project Work

To study –

MRR

Grain size

Hardness

Roughness

Of different work materials. On the basis of the experiments carried out an analysis is

being done for the materials that which parameters do substantially affect the results and

which set of parameters are best for that material under given conditions.

The study would provide a mathematical approach towards working with

different materials, different conditions and then evaluating results completely based upon the

experimentation on the machine.

The logical reasoning based on the observations and the theories given by

renowned scientists would help us to justify what had been said/ written.

Parameters selected for variation on EDM –

Voltage

Current

Lift

On the selected materials i.e.

1. S30400 – (85×77×12)mm Density = .1257gm/cm3

[6]Austenitic Stainless Steel

Cr Ni C Mn Si P S Mo N

18-20 8-10.5 0.08 2.0 0.75 0.045 .03 2-3 .10

2. D2 - (167×77×12)mm Density = 7.7gm/cm3

High Carbon High Chromium Steel

[7]Tool Steel

C Cr Mo V Si Mn

1.55 12.0 0.8 0.9 0.25 0.35

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Chapter – 2

Literature Review

2.1 Spark Erosion Machining Process

V

I

Fig 2.1 Schematic representation of the basic working principle of EDM process

In EDM, a potential difference is applied between the tool and work piece. The tool and the

work material are immersed in a dielectric medium. Generally kerosene or deionized water is

used as the dielectric medium. A gap is maintained between the tool and the work piece. As

the electric field is established between the tool and the job, the free electrons on the tool are

subjected to electrostatic forces. If the work function or the bonding energy of the electrons is

less, electrons would be emitted from the tool (assuming it to be connected to the negative

terminal). Such emission of electrons is termed as cold emission. The “cold emitted”

electrons are then accelerated towards the job. As they gain velocity and energy, there would

be collisions between the electrons and dielectric molecules. Such collision may result in

ionization of the dielectric molecule depending upon the work function of the dielectric

molecule and the energy of the electron. Thus, as the electrons get accelerated, more positive

ions and electrons would get generated due to collisions. This cyclic process would increase

the concentration of electrons and ions in the dielectric medium between the tool and the job

at the spark gap. The concentration would be so high that the matter existing in that channel

could be characterized as “plasma”. The electrical resistance of such plasma channel would

be very less. A large number of electrons will flow from the tool to the job and ions from the

job to the tool called avalanche motion of electrons. Such movement of electrons and ions

can be visually seen as a spark. Thus the electrical energy is dissipated as the thermal energy

of the spark. The high speed electrons then impinge on the job and ions on the tool. The

kinetic energy of the electrons and ions on impact with the surface of the job and tool

respectively converted into thermal energy. It leads to extreme instantaneous confined rise

in temperature which would be nearly 10,000oC.

This leads to material removal. Material removal occurs due to instant vaporization of the

material as well as due to melting. The molten metal is not removed completely but only

partially. As the potential difference is withdrawn as shown in Fig. 2.1, the plasma channel is no longer

sustained. As the plasma channel collapse, it generates pressure, which evacuates the molten

material forming a crater of removed material around the site of the spark.

Thus to summarize, the material removal in EDM mainly occurs due to formation of shock

waves as the plasma channel collapse owing to discontinuation of applied potential

difference. Generally the work piece is made positive and the tool negative. Hence, the electrons strike

the job leading to crater formation due to high temperature and melting and material removal.

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Similarly, the positive ions impinge on the tool leading to tool wear. In EDM, the generator is

used to apply voltage pulses between the tool and the job. A constant voltage is not applied.

Only sparking is desired in EDM rather than arcing. Arcing leads to localized material

removal at a particular point whereas sparks get distributed all over the tool surface leading

to uniformly distributed material removal under the tool.[1]

Fig. 2.3 Waveform used in EDM

2.2 Spark Erosion Generators :

Relaxation Generators

Fig. 2.2 Elementary relaxation generator for EDM[3]

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In RC type generator, the capacitor is charged from a DC source. As long as the voltage in the

capacitor is not reaching the breakdown voltage of the dielectric medium under the prevailing

machining condition, capacitor would continue to charge. Once the breakdown voltage is

reached the capacitor would start discharging and a spark would be established between the

tool and work piece leading to machining. Such discharging would continue as long as the

spark can be sustained. Once the voltage becomes too low to sustain the spark, the

charging of the capacitor would continue. Fig. 2.2 shows the working of RC type EDM

relaxation.

The waveform is characterised by the

• The open circuit voltage - Vo

• The working voltage - Vw

• The maximum current - Io

• The pulse on time – the duration for which the voltage pulse is applied - ton

• The pulse off time - toff

• The gap between the work piece and the tool – spark gap - δ • The polarity – straight polarity – tool (-ve) • The dielectric medium • External flushing through the spark gap.

During charging, at any instant, from circuit theory :

Vc = V0 { 1 – e (-t/RcC)

}

where, Ic = charging current

Vo= open circuit voltage

Rc= charging resistance

C = capacitance Vc= instantaneous capacitor voltage during charging

Ic = V0 - Vc = V0 - V0 { 1 – e (-t/RcC)

}

Rc Rc

2.2.1 Lift – It is entered manually with dimension mm. It is that distance covered by the

electode during which the dielectric deionizes or the capacitor recharges. It can be concluded

that it is part of Toff i.e the time during which no machining is done.

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Stages defined to understand Lift –

Suppose - Lift = 0.2 mm

Spark Gap (for same Breakdown Voltage) = 0.05mm

Machining (in one cycle) = 0.01mm

Stage 1 – Start

Tool

20

Workpiece 10

Stage 2 – Electrode moves down , Charging of Condenser

10 10.05

Stage 3 – Just after machining

9.99 10 10.04

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Stage 4 – After Machining , Reionization of dielectric

10.24

Stage 5 – Recharging of capacitor

10.04

And the same process repeats and the machining is performed.

2.2.2 Electrode Feed Control

Fig. 2.4 Electrode Feed Control in EDM [3]

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If the tool is stationary relative to the workpiece, the gap increases as the material removal

progresses, necessitating an increased voltage to initiate the sparks. To avoid this problem,

the tool is fed with the help of a servodrive which senses the magnitude of the working gap

and keeps it constant. [4]

[3]Since during operation both the work piece and electrode are eroded, the feed control must

maintain a movement of the electrode towards the work piece at such a speed that the

working gap and hence, the sparking voltage remains unaltered. Since the gap width is so

small, any tendency of the control mechanism to hunt is highly undesirable. Rapid response

of the mechanism is essential and this implies a low inertia force. Overshooting may close the

gap and cause a short circuit; hence, it is essential to have rapid reversing speed with no

backlash. Servo mechanisms affecting the movement of the electrode may be either electric

motor driven, solenoid operated or hydraulically operated or the combination of these. An

electric motor driven type of gap control mechanism is shown in fig. 2.4. Here the electrode

is carried in a chuck fixed to a spindle, to which a rack is attached. The axial movement of

the spindle is controlled through a reduction gearbox driven by a D.C. shunt motor, which is

reversible so that the electrode can be withdrawn, should the gap be bridged by swarf or the

control mechanism cause the electrode to overshoot.

Assume the electrode to be initially widely spaced from the work piece and the

current supply switched on to the condenser. This will cause the condenser to be charged and

the voltage will rise to approach the supply voltage. The supply voltage will prevail across

one lower arm of the bridge. The voltage across another arm of the bridge will depend on the

potentiometer setting. This voltage tends to rotate the motor, causing the electrode to close

the gap. When the electrode reaches the correct position, sparking takes place and the

condenser rapidly charges and discharges so that a saw-tooth waveform is produced across its

terminals. The electrode will cease to move when the average value of this voltage equals that

prevailing across lower limb of potentiometer. Under this condition the bridge is balanced

and there is no armature current.

Should the electrode overshoot, the gap width will be smaller and the average

condenser voltage will fall since the condenser will no longer be able to charge up to the

specific voltage. The bridge is now unbalanced with a reverse polarity so the motor reverses

and widens the gap until the correct position is attained. A similar action takes place when the

gap is bridges by swarf (small spherical particle).

After the discharge, the dielectric deionizes, the capacitor is recharged and the

cycle repeats itself.

A discharge across the working gap will occur if the Vc (instantaneous

capacitor voltage during charging) equals the breakdown voltage of the

dielectric.

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2.3 The EDM sequence:

The graphics below simulate the stages of a single electrical discharge. Submerged within a

dielectric, the positive electrode is shown on top and is slowly approaching the negative-

polarity work piece. The tables within the blue fields show voltage and amperage running on

a horizontal time table.

In the first panel, we have a high potential voltage or “open gap” voltage as the electrode is

“cutting air”. As it nears the work piece, it creates a strong electromagnetic field. In panel 2,

this field increases, attracting and polarizing ions within the dielectric, reducing its resistivity.

Open-gap voltage is at its maximum. In the 3rd panel, dielectric resistance is overcome and

the potential voltage crosses the gap in the form of an arc. The volt meter drops to show

“cutting voltage” and amperage can be measured as current is generated. On-time and

electrical discharge machining has begun.

The plasma-hot spark vaporizes the work piece and everything it contacts, including the

dielectric, so a sheath of vaporized gasses from the dielectric encases the spark and creates a

rapidly expanding gas bubble. In the middle panel, both voltage and amperage begin to level

off as the crater on the work piece and the gas bubble get larger. Dielectric damage and

contamination begin to increase the dielectric’s resistivity. On the far right, the dielectric has

become too contaminated to support stable machining. At this point, without a change, a

damaging arc or wire-break will occur.

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This necessary change is switching the current off and entering the off-time phase of EDM.

With the heat source of the spark removed, the gas bubble collapses and implodes upon itself

and upon rebounding from this collision; hot, damaged and contaminated dielectric is ejected

from the arc-site, aiding flushing. In the last two panels, the EDM’ed crater is visible but no

work or machining is done during off-time to allow flushing and/or time for dielectric

reionization and the repetition of this cycle. [5]

2.4 Advantages of using EDM as the machining process:

a. The process can be readily applied to electrically conductive materials.

Physical and metallurgical properties of the work material, such as strength,

toughness, microstructure, etc., are no barrier to its application.

b. During machining the work piece is not subjected to mechanical deformation

as there is no physical contact between tool and work. This makes the process

more versatile. As a result, slender and fragile jobs can be machined

conveniently.

c. Although the material removal in this case is due to thermal effects, there is no

heating in the bulk of material.

d. Complicated die contours in hard materials can be produced to high degree of

accuracy and surface finish.

e. The overall production rate compares well with the conventional processes

because it can dispense with operations like grinding, etc.

f. The surface produced by EDM consists of a multitude of small craters. This

may help in oil retention and better lubrication, specially for components

where lubrication is a problem. The random distribution of craters does not

result in an appreciable reduction in fatigue strength of the components

machined by EDM.

g. The process can be automated easily requiring very little attention from the

machine operator. [3]

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2.5 Gap Sense

Though the surfaces may appear smooth, asperities and irregularities are always

present (in an exaggerated manner, of course). The two points having the minimum distance

between them, spark occurs and the distance increases. Then the next location of shortest gap

is sensed and the spark occurs there between the electrodes. The cycle repeats thereafter.

Generally, the rate of material removal from the cathode is comparatively less

than that from the anode due to following reasons:

a) The momentum with which the stream of electrons strikes the anode is much more

than due to the stream of positive ions impinging on the cathode though the mass of

an individual electron is less than that of the positive ions.

b) The pyrolysis of the dielectric fluid (normally a hydrocarbon) creates a thin film of

carbon on the cathode.

c) A compressive force is developed at the cathode surface. [4]

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Chapter – 3

Concept and Theory of the problem

3.1 Apparatus and Material Used

Characteristics of EDM SN125

Tank Size (mm) 600*400*275

Table Size (mm) 400*300

Long Cross Travel (mm)` 200*150

Quill (mm) 200

Maximum height of work piece (mm) 225

Max. Electrode weight (Kg) 35

Parallelism of the table surface with

travel

0.02

Squareness of the electrode travel 0.02/300

3.2 Material Used

1. S30400 – (85×77×12)mm Density = .1257gm/cm3

[6]Austenitic Stainless Steel

Cr Ni C Mn Si P S Mo N

18-20 8-10.5 0.08 2.0 0.75 0.045 .03 2-3 .10

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2. D2 - (167×77×12)mm Density = 7.7gm/cm3

High Carbon High Chromium Steel

[7]Tool Steel

C Cr Mo V Si Mn

1.55 12.0 0.8 0.9 0.25 0.35

3.3 Design of Experiment

3.3.1 Parameters varied on EDM:-

1. Voltage (volt)

30 50 60 75 90

2. Current (ampere)

5 10 15

3. Lift (mm)

0.2 0.4

3.3.2 Properties to be studied:-

a. Material Removal Rate

` MRR (cm3/minute) = Work piece weight loss(grams)

Density (gm/cm3) × machining time (minutes)

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b. Grain No.

Grain No. = In the metallographic laboratory, analyzing grains in metallic

and alloy samples, such as aluminum or steel, is important for quality-control.

Most metals are crystalline in nature and contain internal boundaries,

commonly known as "grain boundaries". When a metal or alloy is processed,

the atoms within each growing grain are lined up in a specific pattern,

depending on the crystal structure of sample. With growth, each grain will

eventually impact others and form an interface where the atomic orientations

differ. It has been established that the mechanical properties of the sample

improve as the grain size decreases. Therefore, alloy composition and

processing must be carefully controlled to obtain the desired grain size.[8]

Measurement - Estimate the average grain size by counting (on the ground-

glass screen, on a photomicrograph of a representative field of the specimen, a

monitor or on the specimen itself) the number of grains intercepted by one or

more straight lines sufficiently long to yield at least 50 intercepts. It is

desirable to select a combination of test line length and magnification such

that a single field will yield the required number of intercepts. One such test

will nominally allow estimation of grain size to the nearest whole ASTM size

number.

Intercept – a segment of test line overlaying one grain.

Intersection – a point where a test line is cut by a grain boundary [9]

c. Hardness - Indentation hardness measures the resistance of a sample to material

deformation due to a constant compression load from a sharp object; they are

primarily used in engineering and metallurgy fields.

Common indentation hardness scales are Rockwell, Vickers, Shore, and Brinell.

Apparatus - Rockwell Hardness Tester

100 Kg against 10 Kg

Ball Indentor – Steel Ball indentor Diameter = 1/16 inches

Scale – Rockwell C

d. Roughness - Roughness consists of surface irregularities which result from the

various machining process. These irregularities combine to form surface texture.

https://en.wikipedia.org/wiki/Engineering

https://en.wikipedia.org/wiki/Metallurgy

https://en.wikipedia.org/wiki/Rockwell_scale

https://en.wikipedia.org/wiki/Vickers_hardness_test

https://en.wikipedia.org/wiki/Shore_scale

https://en.wikipedia.org/wiki/Brinell_hardness_test

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Apparatus – Contact Profilometer

• A diamond stylus moved vertically in contact with a sample and then moved laterally

across the sample for a specified distance and specified contact force.

• Measure small surface variations in vertical stylus displacement as a function of

position.

• The height position generates an analog signal which is converted into a digital signal,

stored, analysed, and displayed.

• Equipment standard – JIS scale Rz

• Radius of diamond stylus ranges from 20 nanometres -50 micrometres.

• Equipment Displacement – 0.8 mm/sec. × 3sec.

3.3.3 Methodology of experiment: Taguchi Technique

In this study, the material removal rate, hardness, grain size, surface roughness were analysed on

the basis of maximum and minimum values respectively. So by taguchi method “higher is better”

chooses for mrr and “smaller is better” for surface roughness. The results were analysed on S/N

ratio which is based on Taguchi method.

Higher is better

(S/N)HB = -10log (MSDHB)

Where MSDHB = 1/r ∑ri=1 [1/ (yi

2)]

MSDHB = Mean Square Deviation for Higher the better response

r = no. of trials

yi = the ith

measured value in a row

Smaller is better

(S/N)LB = -10log (MSDLB)

Where MSDLB = 1/r ∑ri=1 [1/ (yi

2)]

MSDLB = Mean Square Deviation for Lower the better response [10]

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Chapter-4

Performance Analysis

4.1 Experimental Data

4.1.1 S30400 – (85×77×12)mm Density = .1257gm/cm3



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Work Hole 4 5 6 9 8 7 12 10

Lift(mm) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

Current

(amp) 14(10) 8(5) 23(15) 15(15) 5(5) 10(10) 8(15) 3(5)

Voltage

(volt) 30 30 30 50 50 50 75 75

MRR

(cm3/min)

2.713 1.420 4.419 2.788 0.962 1.606 1.301 0.459

S/N ratio 8.664 3.045 12.924 8.928 -0.334 4.123 2.291 -6.763

Grain Size 4.5 5 2.5 5.5 5 4.5 5 6.5

Threshold 135 133 147 110 110 130 126 120

Hardness

(HRC) 7 18 6 8 14 16 11 5

Roughness

(µm) 63.55 73.88 75.01 72.14 46.34 63.79 60.57 43.45

S/N ratio 36.06 37.37 37.50 37.16 33.31 36.09 32.64 32.76


Work Hole 6 5 4 1 2 3 8 7 Lift(mm) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

Current

(amp) 5(5) 10(10) 15(15) 4(5) 8(10) 12(15) 4(10) 8(15)

Voltage

(volt) 65 65 65 80 80 80 95 95

MRR

(cm3/min)

0.568 1.212 1.894 0.514 1.075 1.681 0.958 0.871

S/N ratio -4.91 1.67 5.547 -5.78 0.628 4.511 -0.37 -1.2 Grain Size 4.5 5 3.5 3 3 3.5 3 Threshold 47 40 41 52 42 51 37 Hardness

(HRC) 13 9 25 16 13 12 9 8

Roughness

(µm) 62.34 52.02 66.37 65.63 76.09 101.0 60.63 82.77

S/N ratio 35.89 34.32 36.44 36.34 37.62 40.08 35.65 38.35

18 | P a g e

4.1.2 D2 - (167×77×12)mm Density = 7.7gm/cm3

Fig. D2 machined surface

19 | P a g e


Work Hole 3 2 4 5 6 7 8 9 Lift(mm) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

Current

(amp) 5(5) 8(10) 15(15) 4(5) 7(10) 11(15) 2(5) 7(15)

Voltage

(volt) 60 60 60 75 75 75 90 90

MRR

(cm3/min.)

0.031 .05 .076 .017 .046 .074 .013 .047

S/N ratio -30.17 -26.02 -22.38 -35.39 -26.74 -22.61 -37.72 -26.55 Grain Size 3 2 3 4 3.5 2.5 3.5 1.5 Threshold 46 38 37 41 40 42 44 47 Hardness

(HRC) 26 22 23 17 20 20 21 19

Roughness

(µm) 58.04 75.01 72.91 58.29 63.99 94.64 56.53 64.23

S/N ratio 35.27 37.50 37.25 35.31 36.12 39.52 35.04 36.15


Work

Hole 12 11 13 14 15 16 17 10 18

Lift(mm) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

Current

(amp) 4(5) 8(10) 13(15) 2(5) 5(10) 8(15) 1(5) 3(10) 7(15)

Voltage

(volt) 60 60 60 75 75 75 90 90 90

MRR

(cm3/min.)

.013 .035 .051 .011 .028 .042 .005 .012 .02

S/N ratio -37.72 -29.11 -25.84 -39.17 -31.05 -27.53 -46.02 -38.41 -33.98

Grain Size 2.5 3.5 2.5 3 3.5 2.5 3.5 3.5 3.5

Threshold 39 40 42 42 45 50 49 39 42

Hardness

(HRC) 25 20 7 17 17 31 19 10

Roughness

(µm) 48.17 65.07 59.67 64.48 61.68 92.20 52.14 81.45 64.12

S/N ratio 33.65 36.26 35.51 36.18 35.80 39.29 34.34 38.21 36.13

20 | P a g e

4.2 Study of Properties:-

4.2.1 Effect of parameters on MRR:- 1. SS304


3.045

8.664

12.924

0

2

4

6

8

10

12

14

8 14 23

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.2mm

30V

-0.334

4.123

8.928

-2

0

2

4

6

8

10

5 10 15

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.2mm

50V

-6.763

2.291

-8

-6

-4

-2

0

2

4

3 8

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.2mm

75V

21 | P a g e


-4.91

1.67

5.547

-6

-4

-2

0

2

4

6

8

5 10 15

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.4mm

65V

-5.78

0.628

4.511

-8

-6

-4

-2

0

2

4

6

4 8 12

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.4mm

80V

-0.37

-1.2

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

4 8

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.4mm

95V

22 | P a g e

2. D2


-30.17

-26.02 -22.38

-35

-30

-25

-20

-15

-10

-5

0

5 8 15

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.2mm

60V

-35.39

-26.74 -22.61

-40

-30

-20

-10

0

4 7 11

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.2mm

75V

-37.72

-26.55

-40

-30

-20

-10

0

2 7

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.2mm

90V

23 | P a g e


-37.72

-29.11 -25.84

-40

-30

-20

-10

0

4 8 13

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.4mm

60V

-39.17

-31.05 -27.53

-50

-40

-30

-20

-10

0

2 5 8

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.4mm

75V

-46.02

-38.41 -33.98

-50

-40

-30

-20

-10

0

1 3 7

S/N

rat

io f

or

MR

R

Ampere

Lift = 0.4mm

90V

24 | P a g e

4.2.2 Effect of parameters on Grain Size 1. SS304

25 | P a g e



8, 5

14, 4.5

23, 2.5

5, 5

10, 4.5

15, 5.5

3, 6.5

8, 5

0

1

2

3

4

5

6

7

0 5 10 15 20 25

Gra

in S

ize

Current

Lift = 0.2mm

30V

50V

75V

5, 4.5 10, 5

15, 3.5

4, 3 8, 3 12, 3.5

4, 3

0

1

2

3

4

5

6

0 2 4 6 8 10 12 14 16

Gra

in S

ize

Current

Lift = 0.4mm

65V

80V

95V

26 | P a g e

2. D2

27 | P a g e



5, 3

8, 2

15, 3

4, 4

7, 3.5

11, 2.5

2, 3.5

7, 1.5

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 2 4 6 8 10 12 14 16

Gra

in S

ize

Current

Lift = 0.2mm

60V

75V

90V

4, 2.5

8, 3.5

13, 2.5

2, 3

5, 3.5

8, 2.5

1, 3.5 3, 3.5 7, 3.5

0

0.5

1

1.5

2

2.5

3

3.5

4

0 2 4 6 8 10 12 14

Gra

in S

ize

Current

Lift = 0.4mm

60V

75V

90V

28 | P a g e

4.2.3 Effect of parameters on Hardness 1. S304



8, 18

14, 7 23, 6

5, 14

10, 16

15, 8

3, 5

8, 11

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25

Har

dn

ess

HR

C

Current

Lift = 0.2mm

30V

50V

75V

5, 13

10, 9

15, 25

4, 16

8, 13

12, 12

4, 9 8, 8

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14 16

Har

dn

ess

HR

C

Current

Lift = 0.4mm

65V

80V

95V

29 | P a g e

2. D2



5, 26

8, 22 15, 23

4, 17

7, 20

11, 20 2, 21

7, 19

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14 16

Har

dn

ess

HR

C

Current

Lift = 0.2mm

60V

75V

90V

4, 25

8, 20

13, 7

2, 17

5, 17

8, 31

1, 19

7, 10

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14

Har

dn

ess

HR

C

Current

Lift = 0.4mm

60V

75V

90V

30 | P a g e

4.2.4 Effect of parameters on Roughness 1.SS304



8, 37.37

14, 36.06

23, 37.5

5, 33.31

10, 36.09

15, 37.16

3, 32.76 8, 32.64

32

33

34

35

36

37

38

0 5 10 15 20 25

S/N

rat

io f

or

Ro

ugh

nes

s

Current

Lift = 0.2 mm

30V

50V

75V

5, 35.89

10, 34.32

15, 36.44 4, 36.34

8, 37.62

12, 40.08

4, 35.65

8, 38.35

34

35

36

37

38

39

40

41

0 2 4 6 8 10 12 14 16

S/N

rat

io f

or

Ro

ugh

nes

s

Current

Lift = 0.4 mm

65V

80V

95V

31 | P a g e

2. D2

Graph 4.15 S/N ratio for Roughness v/s Current for D2 with Lift 0.2mm

Graph 4.16 S/N ratio for Roughness v/s Current for D2, Lift 0.4mm

5, 35.27

8, 37.5

15, 37.25

4, 35.31

7, 36.12

11, 39.52

2, 35.04

7, 36.15

34.5

35

35.5

36

36.5

37

37.5

38

38.5

39

39.5

40

0 2 4 6 8 10 12 14 16

S/N

rat

io f

or

Ro

ugh

nes

s

Current

Lift = 0.2 mm

60V

75V

90V

4, 33.65

8, 36.26

13, 35.51

2, 36.18 5, 35.8

8, 39.29

1, 34.34

3, 38.21

4, 36.13

33

34

35

36

37

38

39

40

0 2 4 6 8 10 12 14

S/N

rat

io f

or

Ro

ugh

nes

s

Current

Lift = 0.4 mm

60V

75V

90V

32 | P a g e

Chapter – 5

Results and Discussions

5.1 Optimal set of parameters for SS304

a) On the basis of MRR – Higher is Better

Lift(mm) Current(Ampere) Voltage(Volt) MRR (cm3/min.) S/N

ratio

0.2 23(15) 30 4.419 12.924

b) On the basis of Grain Size – Lower the grain size, better will be the

mechanical properties

Lift(mm) Current(Ampere) Voltage(Volt) Grain Size Threshold

0.2 23(15) 30 2.5 147

c) On the basis of Hardness – Higher is better

Lift(mm) Current(Ampere) Voltage(Volt) HRC

0.4 15(15) 65 25

d) On the basis of Roughness – Lower is better

Lift(mm) Current(Ampere) Voltage(Volt) Roughness(µm) S/N

ratio

0.2 5(5) 50 46.34 33.31

33 | P a g e

5.2 Optimal set of parameters for D2

a) On the basis of MRR – Higher is Better

Lift(mm) Current(Ampere) Voltage(Volt) MRR (cm3/min.) S/N ratio

0.2 15(15) 60 0.076 -22.38

b) On the basis of Grain Size – Lower the grain size, better will be the

mechanical properties

Lift(mm) Current(Ampere) Voltage(Volt) Grain Size Threshold

0.2 8(10) 60 2 40

c) On the basis of Hardness – Higher is better

Lift(mm) Current(Ampere) Voltage(Volt) HRC

0.4 8(15) 75 31

d) On the basis of Roughness – Lower is better

Lift(mm) Current(Ampere) Voltage(Volt) Roughness(µm) S/N

ratio

0.4 4(5) 60 48.17 33.65

Discussions

For better MRR we concluded high current, low voltages,

lower lift

For lower Grain Size – Lower current, higher voltages,

higher lift

For Hardness – Higher voltages, higher current, higher lift

For Good surface finish - current lower, voltages at mid

values, higher lift

Current Voltage Lift

Good MRR High Low Low

Lower Grain Size Low High High

Hardness High High High

Surface Finish Low Mid values Higher

34 | P a g e

References

[1] pdf/Lesson-39 Electro Discharge Machining/Module-9 Non

Conventional Machining/ Version-2 ME IIT Kharagpur/www.nptel.ac.in,

assessed on 15.09.2015

[2] pdf/Sushil Kumar Choudhary and R.S Jadoun, Current Advanced

Research Development of Electric Discharge Machining (EDM): A

Review/ International Journal of Research in Advent Technology, Vol.2,

No.3, March 2014 E-ISSN: 2321-9637/www.ijrat.org, pp. 273,


[3] P.C Pandey and H.S Shan, Modern Machining Processes,Affiliated

TMH 1981, ISBN-13:9/8-0-07-096553-9/Chapter-4, Thermal Metal

Removal processes,pp.84-93, assessed on 17.03.2016

[4] Amitabha Ghosh and Asok Kumar Mallik, Manufacturing Science,

Edition-2,Affiliated East-West Press Pvt. Ltd. (2010), ISBN 978-81-7671-

063-3, pp.371, assessed on 15.09.2015

[5] pdf/Bud Guitrau, The Fundamentals of EDM,mmadou.eng.uci.edu,

pp.4, assessed on 09.03.2016

[6]pdf/aksteel.com/markets_products/stainless/austenitic/316_316l_data_s

heet, assessed on 08.02.2016

[7] google.com/D2 Tool Steel - High-Carbon, High-Chromium, Cold-

Work Steel (UNS T30402)/article id -6214/azom.com,


[8] google.com/Grain size analysis in metals and

alloys/applications/olympus-ims.com, assessed on 13.04.2016

[9] pdf/Standard Test Methods for Determining Average Grain

Size/ASTM International/Designation:E112-12/www.researchgate.net, pp.

10, assessed on 13.04.2016

[10] pdf/Suraj Choudhary, Krishan Kant & Parveen Saini/Analysis of

MRR and SR with Different Electrode for SS 316 on Die-Sinking EDM

using Taguchi Technique, Volume 13 Issue 3 Version 1.0 Year 2013,

Publisher: Global Journals Inc. (USA)

Online ISSN: 2249-4596 Print ISSN:0975-5861/Global Journal of

Researches in Engineering, Mechanical and Mechanics

Engineering/www.globaljournals.org, assessed on 26.10.2015

35 | P a g e

Appendix

Grain Size analysis for SS304

Lift = 0.4mm

Work hole = 5

Lift = 0.4mm

Work hole = 8

36 | P a g e

Lift = 0.4mm

Work hole = 2

Lift = 0.4mm

Work hole = 3

37 | P a g e

Grain size analysis for D2

Lift = 0.4mm

Work hole = 4

Lift = 0.2mm

Work hole = 9

38 | P a g e

Lift = 0.2mm

Work hole = 7

Lift = 0.2mm

Work hole = 8

39 | P a g e

Lift = 0.2mm

Work hole = 5

Lift = 0.2mm

Work hole = 6

40 | P a g e

Lift = 0.2mm

Work hole = 3

Lift = 0.2mm

Work hole = 4

41 | P a g e

Lift = 0.2mm

Work hole = 1

Lift = 0.2mm

Work hole = 2

42 | P a g e

Lift = 0.4mm

Work hole 17

Lift = 0.4mm

Workhole 18

43 | P a g e

Lift = 0.4mm

Work hole 16

Lift = 0.4mm

Work hole 15

44 | P a g e

Lift = 0.4mm

Work hole 14

Lift = 0.4mm

Work hole 13

45 | P a g e

Lift = 0.4mm

Work hole 12

Lift = 0.4mm

Work hole 11

46 | P a g e

Lift = 0.4mm

Work hole 10

Project on EDM

Engineering

Transcript of Project on EDM