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 10,000o
C.
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.

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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 ∑r
i=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 ∑r
i=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/NratioforMRR
Ampere
Lift = 0.2mm
30V
-0.334
4.123
8.928
-2
0
2
4
6
8
10
5 10 15
S/NratioforMRR
Ampere
Lift = 0.2mm
50V
-6.763
2.291
-8
-6
-4
-2
0
2
4
3 8
S/NratioforMRR
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/NratioforMRR
Ampere
Lift = 0.4mm
65V
-5.78
0.628
4.511
-8
-6
-4
-2
0
2
4
6
4 8 12
S/NratioforMRR
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/NratioforMRR
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/NratioforMRR
Ampere
Lift = 0.2mm
60V
-35.39
-26.74
-22.61
-40
-30
-20
-10
0
4 7 11
S/NratioforMRR
Ampere
Lift = 0.2mm
75V
-37.72
-26.55
-40
-30
-20
-10
0
2 7
S/NratioforMRR
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/NratioforMRR
Ampere
Lift = 0.4mm
60V
-39.17
-31.05
-27.53
-50
-40
-30
-20
-10
0
2 5 8
S/NratioforMRR
Ampere
Lift = 0.4mm
75V
-46.02
-38.41
-33.98
-50
-40
-30
-20
-10
0
1 3 7
S/NratioforMRR
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
GrainSize
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
GrainSize
Current
Lift = 0.4mm
65V
80V
95V

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
GrainSize
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
GrainSize
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
HardnessHRC
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
HardnessHRC
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
HardnessHRC
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
HardnessHRC
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/NratioforRoughness
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
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
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
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

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