This document summarizes a study on optimizing electric discharge machining (EDM) parameters to maximize material removal rate (MRR) and minimize electrode wear rate (EWR) when machining stainless steel 316 with a copper electrode. Experiments were conducted using a Taguchi design of experiments with four machining parameters (pulse on time, pulse off time, current, fluid pressure) each at three levels. Results showed that pulse off time and current had the most significant effects on MRR and EWR, respectively. Specifically, MRR increased with longer pulse off times while EWR decreased at higher currents. The optimal settings found were a current of 12 amps and long pulse off time to achieve maximum MRR during EDM of

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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
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IJMET
© I A E M E
EFFECT OF EDM PARAMETERS IN OBTAINING MAXIMUM MRR AND
MINIMUM EWR BY MACHINING SS 316 USING COPPER ELECTRODE
Abhishek Gaikwad1, Amit Tiwari2, Amit Kumar3, Dhananjay Singh4
Assistant Professor1, Scholars2, 3, 4
(Department of Mechanical Engineering, SSET, SHIATS, Naini Allahabad Uttar Pradesh, India
ABSTRACT
EDM machining is used for very hard and complex cutting of conducting materials with
higher surface finish and close dimensions. EDM process parameters are affected by both electrical
and non electrical parameters. In this paper, cutting of hard material Stainless steel 316 is done on
electro discharge machine with copper as cutting tool electrode. This paper presents the effect of
control factors (i.e., current, pulse on time, pulse off time, fluid pressure) for maximum material
removal rate (MRR) and minimum electrode wear rate (EWR) for die sinking Electric Discharge
Machine. In this paper both the electrical factors and non electrical factors has been focused which
governs MRR and EWR. Paper is based on Design of experiment and optimization of EDM process
parameters. The technique used is Taguchi technique which is a statistical decision making tool helps
in minimizing the number of experiments and the error associated with it. The research showed that
the Pulse off time, Current has significant effect on material removal rate and electrode wear rate
respectively.
Keywords: Electro Discharge Machine, Electrode Wear Rate, Material Removal Rate, SS 316,
Taguchi Technique.
1. INTRODUCTION
Electrical Discharge Machining (EDM) is a process of material removal using an accurately
controlled electrical discharge (spark) through a small gap (approximately 10 to 50 microns) filled
with dielectric fluid between an electrode and a workpiece. The technique allows machining high-strength
and wear-resistance materials such as high-strength alloys, polycrystalline diamond and

2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
ceramic (ultra-hard conductive material) since the hardness of the workpiece has no effect on the
process. Unlike the traditional cutting and grinding processes, which depends on the force generated
by a harder tool to remove the softer material workpiece, the EDM process is free from contact force
and chatter vibration. Furthermore, EDM permits the machining to be done even after the hardening
process. The EDM process has been used in high precision machining of metals, and to date, there
are several different types of EDM systems that have been developed for a particular industrial
application. EDM is widely used for making mold and dies and finishing parts for automotive
industry, aerospace and surgical components [1]. Two principle types of EDM processes are the die
sinking and the wire cut EDM process. Die sinking type EDM machine requires an electrode to
machine the workpiece. Wire cut EDM machine uses a continuous wire as the electrode to cut the
workpiece. Rajurkar [2] explained some future trends study in EDM such as machining advanced
materials, mirror surface finish using powder additives, ultrasonic-assisted EDM, control and
automation.
102
One of the field interests is to study the optimal selection of process parameters which will
increase production rate considerably by reducing the machining time. An optimum selection of
machining parameters for the best process performance is still uncertain since EDM process is a
complex and stochastic process.
The objective of the present work is to investigate MRR of SS 316 and EWR of copper by
using die sinking EDM and to optimize these performance characteristics for obtaining maximum
MRR and minimum EWR.
2. EXPERIMENTAL DETAILS
2.1. Experimental Materials
Stainless steel 316 is chosen as the work piece material and copper EC-99 as the tool
electrode material.
Table 1: Chemical composition of stainless steel 316.
Fe C Cr Ni Mo Mn Si P S
remaining 0.03% 16-18.5% 10-14% 2-3% 2% 1% 0.045% 0.03%
Fig 1: SS 316 used for experiment

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
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Table 2: Physical properties of SS 316
Physical Properties Value
Melting point 1375-1400°C
Density 8000 kg/m3
Tensile strength 515 MPa
Yield strength 205 MPa
Elastic modulus 193 GPa
Hardness (HRB) 95
Electric resistivity 740 n.m
Fig 2: Copper electrode used for experiment
Table 3: Copper electrode EC-99 specification
Specifications Value
Purity (%) 99.9
Average particle size 5 micron
Strength (psi)
Bending 16500
Compressive 30000
Density (g/ cm3 ) 67.05
Hardness (shore) 67
Electrical resistance 120 μin
2.2. Experimental Method
Machining was carried out in EDM of Electronic Electra plus C 3822 Die Sinking Machine
as shown in Fig 3. Machine is provided with fixed pulse voltage. The current, fluid pressure, pulse
ON time and pulse OFF time were selected from the range. The working EDM is of maximum
discharge current capacity of 20 Ampere. A series of experiments have been conducted by varying
parameters such as current, pulse on time, pulse off time, fluid pressure with each has 3 levels.
Commercial grade kerosene is used as dielectric to analyse the effects on MRR as per the Taguchi
orthogonal L9 array. A copper electrode of diameter 5 mm is used as cutting tool and the work piece
of Stainless steel 316 is machined for 10 minutes to record the readings. Observations are taken in
the form of mass of material removed per sec (gram/sec) for both work piece and copper electrode.
Mass lost is measured with accuracy 0.001 milligram. The data collected in MRR and EWR form is
optimized and analyzed by Taguchi technique.
Table 4: Working conditions and description of EDM
Working
conditions
Work piece Electrode Discharge
current
Pulse ON
time
Pulse OFF
time
Fluid
Pressure
Dielectric
fluid
Description Stainless
Steel 316
Copper EC
99
4,8,12
amps
2,4,7 μs 5,8,11 μs 0.2,0.4,0.6
kg/cm2
commercial
grade
kerosene

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
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Fig 3: EDM machine
Table 5: Response parameters and control parameters with their levels
Response
Parameters
Material Removal Rate (gm /min.)
Electrode Wear Rate (gm /min.)
Control Parameters
Levels
1 2 3
Pulse ON time (μs) 2 4 7
Pulse OFF time (μs) 5 8 11
Discharge current (A) 4 8 12
Fluid Pressure ( kg/cm2 ) 0.2 0.4 0.6
3. DESIGN OF EXPERIMENT AND DATA ANALYSIS:
Taguchi is an optimization technique in design of experiment which is combination of
mathematical model (curve fit) and statistical analysis. For 4 controlling variables and 3 level of each
we can draw a L9 orthogonal array.
Table 6: Design Matrix of L9 Orthogonal Array
Exp. No. A B C D
1 1 1 1 1
2 1 2 2 2
3 1 3 3 3
4 2 1 2 3
5 2 2 3 1
6 2 3 1 2
7 3 1 3 2
8 3 2 1 3
9 3 3 2 1

5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
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3.1 Material removal rate
The material removal rate of the work piece is the volume of the material removed per
minute. It can be calculated using the following relation.
The electrode wear rate (EWR) of the electrode is the amount of the tool wear per minute. It
can be calculated using the following equation.
The experiments were conducted based on varying the process parameters, which affects the
machining process to obtain the required quality characteristics. There are 64 such quality
characteristics. The most commonly used are Larger the better, Smaller the better, Nominal the best,
classified attribute and Signed target
In case of MRR, larger the better is taken as it states that the output must be as large as possible,
therefore the S/N Ratio will be given as:
S/N Ratio= -10× Log10 (sum (1/y2)/n)
In case of EWR, smaller the better is opted as it states that the output must be as low as possible,
therefore the S/N Ratio will be given as:
S/N Ratio= -10× Log10 (sum (y2)/n)
Table 7: Design Matrix of L9 Orthogonal Array
Exp.
No.
Pulse on
Time
(μ Sec)
Pulse off
Time
(μ Sec)
Current
(A)
Fluid
Pressure
(Kg/cm3)
M.R.R
gm/min
E.W.R
gm/min
S/N Ratio
(MRR)
S/N Ratio
(EWR)
1 2 5 4 0.2 0.006 0.0015 -44.4370 56.4782
2 2 8 8 0.4 0.012 0.004 -38.4164 47.9588
3 2 11 12 0.6 0.033 0.0015 -29.6297 56.4782
4 4 5 8 0.6 0.007 0.003 -43.0980 50.4576
5 4 8 12 0.2 0.023 0.009 -32.7654 40.9151
6 4 11 4 0.4 0.019 0.001 -34.4249 60.0000
7 7 5 12 0.4 0.040 0.002 -27.9588 53.9794
8 7 8 4 0.6 0.021 0.001 -33.5556 50.0000
9 7 11 8 0.2 0.035 0.002 -29.1186 53.9794
Table 8: S/N Ratio Table for EWR
LEVEL PULSE ON PULSE OFF CURRENT FLUID PRESSURE
1 53.64 53.64 58.83 50.46
2 50.46 49.62 50.80 53.98
3 55.99 56.82 50.46 55.65
DELTA 5.53 7.19 8.37 5.19
RANK 3 2 1 4

6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
Main Effects Plot for SN ratios
Data Means
106
Table 9: Response Mean Table for EWR
LEVEL PULSE ON PULSE OFF CURRENT FLUID PRESSURE
1 0.002333 0.002167 0.001167 0.004167
2 0.004333 0.004667 0.003000 0.002333
3 0.001667 0.001500 0.004167 0.001833
DELTA 0.002667 0.003167 0.003000 0.002333
Table 10: S/N Ratio Table for MRR
LEVEL PULSE ON PULSE OFF CURRENT FLUID PRESSURE
1 -37.49 -38.50 -37.47 -35.44
2 -36.76 -34.91 -36.88 -33.60
3 -30.21 -31.06 -30.12 -35.43
DELTA 7.28 7.44 7.35 1.84
RANK 3 1 2 4
Table 11: Response Mean Table for MRR
LEVEL PULSE ON PULSE OFF CURRENT FLUID PRESSURE
1 0.01700 0.01767 0.01533 0.02133
2 0.01633 0.01867 0.01800 0.02367
3 0.03200 0.02900 0.03200 0.02033
DELTA 0.01567 0.01133 0.01667 0.00333
4. RESULTS AND DISCUSSIONS
2 4 7
-30
-31
-32
-33
-34
-35
-36
-37
-38
-39
5 8 11 4 8 12 0.2 0.4 0.6
pulse on
Mean of SN ratios
pulse off current fluid pressure
Signal-to-noise: Larger is better
Fig 4: Mean of SN Ratio of MRR

7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
Main Effects Plot for Means
Data Means
Main Effects Plot for SN ratios
Data Means
107
2 4 7
0.0325
0.0300
0.0275
0.0250
0.0225
0.0200
0.0175
0.0150
5 8 11 4 8 12 0.2 0.4 0.6
pulse on
Mean of Means
pulse off current fluid pressure
Fig 5: Mean of Means of MRR
2 4 7
59
58
57
56
55
54
53
52
51
50
5 8 11 4 8 12 0.2 0.4 0.6
pulse on
Mean of SN ratios
pulse off current fluid pressure
Signal-to-noise: Smaller is better
Fig 6: Mean of SN Ratio of EWR

8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
Main Effects Plot for Means
Data Means
108
2 4 7
0.005
0.004
0.003
0.002
0.001
5 8 11 4 8 12 0.2 0.4 0.6
pulse on
Mean of Means
pulse off current fluid pressure
Fig 7: Mean of Means of EWR
5. CONCLUSIONS
Material removal rate
• Material removal rate is mainly affected by pulse off time followed by current and MRR is
least affected by fluid pressure.
• Pulse off time contribution is major for MRR. MRR increases with increasing pulse off time.
Optimal setting for MRR in the experiment level is as
Current = 12Amp
Pulse on time = 7 μ sec
Pulse off time = 11 μ sec
Fluid Pressure = 0.4 kg/cm2
Electrode wear rate
• Electrode wear rate is mainly affected by current followed by pulse off time. Electrode wear
rate is least affected by fluid pressure.
• Electrode wear rate decreases with increasing current.
Optimal setting for EWR in the experiment level is as
Current = 4 Amp
Pulse on time = 7 μ sec
Pulse off time = 11 μ sec
Dielectric fluid pressure = 0.6 kg/cm2

9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 101-109 © IAEME
109
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