International Journal of Engineering Trends and Technology (IJETT) – Volume17 Number7–Nov2014
Study of EDM Parameters on Mild Steel Using Brass Electrode
Amit Kumar#1, Abhishek Gaikwad*2, Amit Tiwari#3
# 1,3,
Production Engineering (ME), SSET, Allahabad-211007,
SHIATS, Allahabad, Uttar Pradesh (India)
*2
Assistant Professor, Dept of Mechanical Engineering,
SSET, Allahabad-211007 (U.P)
Abstract— Optimization is one of the techniques used in
manufacturing sectors to arrive for the best manufacturing
conditions, which is an essential need for industries towards
manufacturing of quality products at lower cost. This paper aims
to study of process parameters such as current, pulse ON and
OFF time in Electrical Discharge Machining (EDM) process to
identify the variations in three performance characteristics such
as material removal rate, electrode wear rate, for machining
Mild Steel using brass electrode. Based on the experiments
conducted on L9 orthogonal array, study has been carried out
using Taguchi method. Response tables and graphs were used to
find the optimal levels of parameters in EDM process. The
confirmation experiments were carried out to validate the
optimal results. Thus, the machining parameters for EDM were
optimized for achieving the combined objectives of higher rate of
material removal, lower wear rate on tool, on the work material
considered in this work. The obtained results show that the
Taguchi method study is being effective technique to find the best
machining parameters for EDM process.
performance characteristics with maximum MRR and
minimum EWR, simultaneously.
II. MATERIAL PROPERTIES
A. Workpiece properties
Mild steel is chosen as the work piece material and brass
material is used as the tool electrode material. The work
material properties and the photographic view of workpiece
are given in Table.1and Fig.1.respectively.
TABLE 1
CHEMICAL COMPOSITION OF MILD STEEL
Fe
C
Ni
Mn
98.977% 0.095% 10-14% 0.490%
Si
P
S
0.251% 0.011% 0.014%
Keywords— EDM, EWR, MRR, Taguchi Technique.
I. INTRODUCTION
Electric discharge machining (EDM) has widespread
applications for manufacturing dies and tools to produce
plastics moldings, die casting, and sheet metal dies etc[1][2].
Implementation of EDM process will awaken manufacturing
engineers, product designers, tool engineer and metallurgical
engineers about unique capabilities and benefits of this
process [3].where the process is based on removing material
from a part by means of a series of repeated electrical
discharges between tool called the electrode and the work
piece in the presence of a dielectric fluid [4]. The electrode is
moved toward the work piece until the gap is small enough so
that the impressed voltage is great enough to ionize the
dielectric [5]. Short duration discharges are generated in a
liquid dielectric gap, which separates tool and work piece. The
material is removed with the erosive effect of the electrical
discharges from tool and work piece [6]. EDM does not make
direct contact between the electrode and the work piece where
it can eliminate mechanical stresses chatter and vibration
problems during machining [7]. Materials of any hardness can
be cut as long as the material can conduct electricity [8]. EDM
techniques have developed in many areas. Trends on activities
carried out by researchers depend on the interest of the
researchers and the availability of the technology.
The objective of the present work is to investigate
MRR and EWR on EDM of Mild Steel and to optimize these
ISSN: 2231-5381
Fig 1 Mild Steel used for experiment
B. Electrode (Tool) Properties
In this experiment brass is selected as a tool material. The
physical properties of electrode material and the photographic
view of electrode are given in Table.2 and Fig.2 respectively.
TABLE 2
PHYSICAL PROPERTIES OF ELECTRODE MATERIAL
Properties
Cu-Zn (60-40)
Melting point (oC)
910
Density (g/cm3)
10.98 g / cm3
o
Electrical conductivity(I.A.C.S% at 20 C)
78~85
Hardness(HRB)
93
Elastic modulus (GPa)
648
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International Journal of Engineering Trends and Technology (IJETT) – Volume17 Number7–Nov2014
Fig 2 brass electrode used for experiment
III. EXPERIMENTAL DATA
The machining parameters chosen for the present experiment
are Pulse-on time (ton) is the duration of time (in µs). The
discharge current, Ip (in Amp) is allowed to flow per cycle.
Pulse-off time (toff) be the duration of time (in µs) between
two consecutive sparks and fluid pressure (in kg/cm2)
IV. EXPERIMENTAL METHOD
Control parameters selected for the present experiment .i.e.
Discharge current (in Amp),Pulse-on time (in µs). Pulse-off
time (in µs) and fluid pressure (in kg/cm2). Machining was
carried out on EDM of Electronic Electra plus C 3822 Die
Sinking Machine as shown in Fig 3. Machine is provided with
fixed pulse voltage. The control parameters were selected
from the range. EDM has maximum discharge current
capacity of 20 Ampere. A servo mechanism maintains a gap
of about 0.01 to 0.02mm between the electrode & the
workpiece, preventing them from coming into contact with
each other. A direct current of low voltage & high amperage is
delivered to the electrode at the rate of approximately 50 KHz.
These electrical energy impulses vaporize the oil at this point.
This permits the spark to jump the gap between the electrode
and the workpiece through the dielectric fluid. A series of
experiments have been conducted by varying control
parameters such as current, pulse on time, pulse off time, fluid
pressure with each has 3 levels. Commercial grade kerosene is
used as dielectric fluid to analyses the effects on MRR as per
the Taguchi orthogonal L9 array. A brass electrode of
diameter 5 mm is used as cutting tool and the work piece of
Mild steel is machined for 20 minutes to record the readings.
Observations are taken in the form of mass of material
removed per min (gram/min) for both work piece and brass
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.
ISSN: 2231-5381
Fig 3 EDM machine used for experiment
V. MRR AND EWR
MRR = Material Removal Rate
EWR = Electrode Wear Rate
The material removal rate (MRR) of the work piece can be
calculated by using the following equation.
MRR =
The electrode wear rate (EWR) of the electrode can be
calculated by using the following equation.
EWR =
VI. SIGNAL TO NOISE RATIO
Taguchi's emphasis on minimizing deviation from target led
him to develop measures of the process output that
incorporate both the location of the output as well as the
variation. These measures are called signal to noise ratios. The
signal to noise ratio provides a measure of the impact of noise
factors on performance. The larger the S/N, the more robust
the product is against noise.
Calculation of the S/N ratio depends on the experimental
objective:
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International Journal of Engineering Trends and Technology (IJETT) – Volume17 Number7–Nov2014
In Case of MRR: Bigger-the-Better
TABLE 5
EXPERIMANTAL MATRIX OF L9 ORTHOGONAL ARRAY
In Case of EWR: Smaller-the-Better
VII.
DESIGN OF EXPERIMENT AND DATA ANALYSIS
Design of experiment is the step before starting the
experimental work. Design of experiments (DOE) is used to
study the effect of multiple variable simultaneously, which is
a powerful statistical technique introduced by R.A.Fisher in
England in 1920’s.The design of experiment (D.O.E.) chosen
for the electric discharge machining of Mild steel was a
Taguchi L9 orthogonal array, by carrying out a total number
of 9 experiments along with 4 verification experiments
(optional).
In L9 (34) array 9 rows represent the 9 experiment to be
conducted with 4 columns at, 3 levels of the corresponding
factor. The matrix form of these arrays is shown in Table.3
where 1, 2, 3 in the table represents the level of each
parameters.
TABLE 3
LEVEL VALUES OF INPUT FACTOR
Factor
Pulse ON
time (µs)
Pulse OFF
time (µs)
Discharge
current (A)
Fluid
Pressure
( kg/cm2 )
1
4
Levels
2
8
3
12
Pulse Pulse
Exp. on
off Current
No. Time Time (A)
(µ Sec) (µ Sec)
1
4
2
4
2
4
4
6
3
4
6
8
4
8
2
6
5
8
4
8
6
8
6
4
7
12
2
8
8
12
4
4
9
12
6
6
Fluid
Pressure
(Kg/cm3
)
0.1
0.2
0.3
0.3
0.1
0.2
0.2
0.3
0.1
6
4
6
8
LEVEL
Pulse on
Pulse off
0.1
0.2
0.3
1
2
3
DELTA
RANK
42.52
33.28
50.15
16.88
1
40.82
48.37
36.76
11.61
3
ISSN: 2231-5381
Factor B
1
2
3
1
2
3
1
2
3
Factor C Factor D
1
1
2
2
3
3
2
3
3
1
1
2
3
2
1
3
2
1
E.W.R
gm/min
0.0005
0.003
0.007
0.002
0.008
0.006
0.003
0.0015
0.01
0.0065
0.003
0.0215
0.0145
0.037
0.019
0.008
0.0005
0.0075
S/N Ratio S/N Ratio
(MRR)
(EWR)
-66.0206
-50.4576
-43.0980
-53.9794
-41.9382
-44.4370
-50.4576
-56.4782
-40.0000
43.7417
50.4576
33.3512
36.7726
28.6360
34.4249
41.9382
66.0206
42.4988
Current
Fluid
Pressure
TABLE 7
S/N RATIO FOR EWR
4
Factor A
1
1
1
2
2
2
3
3
3
M.R.R
gm/min
TABLE 6
OBSERVATION OF S/N RATIO
2
TABLE 4
DESIGN MATRIX OF L9 ORTHOGONAL ARRAY
Exp. No.
1
2
3
4
5
6
7
8
9
Pulse Pulse
Exp. on
off Current Fluid
No. Time Time
(A)
Pressure
(µ Sec) (µ Sec)
(Kg/cm3)
1
4
2
4
0.1
2
4
4
6
0.2
3
4
6
8
0.3
4
8
2
6
0.3
5
8
4
8
0.1
6
8
6
4
0.2
7
12
2
8
0.2
8
12
4
4
0.3
9
12
6
6
0.1
48.06
43.24
34.64
13.42
2
38.29
42.27
45.38
7.09
4
TABLE 8
RESPONSE MEAN FOR EWR
Fluid
Pressure
LEVEL
Pulse on
Pulse off
Current
1
2
3
DELTA
0.010333
0.023500
0.005333
0.018167
0.009667
0.013500
0.016000
0.006333
0.008667
0.008333
0.022167
0.013833
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0.017000
0.010000
0.012167
0.007000
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International Journal of Engineering Trends and Technology (IJETT) – Volume17 Number7–Nov2014
TABLE 9
S/N RATIO FOR MRR
LEVEL
Pulse on
Pulse off
Main Effects Plot for Means
Data Means
Fluid
Pressure
Current
Pulse on
Pulse off
Current
Fluid Pressure
0.008
-53.19
-46.78
-48.96
6.41
3
-56.82
-49.62
-42.51
14.31
1
-55.65
-48.15
-45.16
10.48
2
-49.32
-48.45
-51.19
2.73
4
TABLE 10
RESPONSE MEAN FOR MRR
LEVEL
Pulse on
Pulse off
Current
1
2
3
DELTA
0.003500
0.005333
0.004833
0.001833
0.001833
0.004167
0.007667
0.005833
0.002667
0.005000
0.006000
0.003333
Fluid
Pressure
0.007
M e an o f M ea n s
1
2
3
DELTA
RANK
0.006
0.005
0.004
0.003
0.006167
0.004000
0.003500
0.002667
0.002
4
8
12
2
4
6
4
6
8
0.1
0.2
0.3
Fig 5 Mean of Means of MRR
VIII.
RESULT AND ANALYSIS
Main Effects Plot for SN ratios
Data Means
Main Effects Plot for SN ratios
Pulse on
Data Means
Pulse off
Current
Fluid Pressure
50
Pulse on
Pulse off
Current
Fluid Pressure
M e an o f SN r at io s
-42
M ean o f SN rat io s
-44
-46
-48
-50
45
40
-52
35
-54
-56
4
8
12
2
4
6
4
6
8
0.1
0.2
0.3
Signal-to-noise: Smaller is better
-58
4
8
12
2
4
6
4
6
8
0.1
0.2
0.3
Fig 6 Mean of SN Ratio of EWR
Signal-to-noise: Larger is better
Fig 4 Mean of SN Ratio of MRR
ISSN: 2231-5381
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International Journal of Engineering Trends and Technology (IJETT) – Volume17 Number7–Nov2014
Main Effects Plot for Means
Data Means
Pulse on
Acknowledgment
Pulse off
Current
Fluid Pressure
0.025
M ea n o f M e an s
0.020
The authors are thankful to faculty members of SSET and M/s
Rajat Engineers and their Technical assistance, staff for giving
full support during the performance of the experiment. The
authors are also extremely thankful to the Head of Department of
Mechanical Engg and research advisor for their motivation during
research work.
REFERENCES
0.015
[1]
[2]
0.010
[3]
0.005
4
8
12
2
4
6
4
6
8
0.1
0.2
0.3
Fig 7 Mean of Means of EWR
IX. CONCLUSIONS
The Die-sinker EDM is widely used machine for machining of
hard material with high precision, high surface finish,
complex profiles. The cost incurred for machining of hard and
complex profile parts is less than the other methods of
machining.
From the results it is found that The Material removal rate is
increased when pulse on time is increased.
MRR mainly affected by current and pulse off time.
MRR least affected by fluid pressure.
Optimum parameters of input factors are as follows:
Current: 8Amp, Pulse on time:8 µ sec, Pulse off time :6 µ sec
Fluid Pressure :0.2 kg/cm2
EWR is mainly affected by current followed by pulse off time.
Electrode wear rate is least affected by fluid pressure.
Optimal parameters of input factors are as follows:
Current: 6Amp, Pulse on time: 12 µ sec, Pulse off time: 2 µ
sec, Fluid Pressure: 0.2 kg/cm2
ISSN: 2231-5381
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BOOKS AND WEBSITES:
Production technology by V.K Jain
Advance manufacturing process by R.K.Rajput
Material Technology by O.P.Khanna
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