Optimization of Process Parameters And Dielectric Fluids on Machining En 31 By Using Topsis

A.Hemantha Kumar. Int. Journal of Engineering Research and Application www.ijera.com
ISSN : 2248-9622, Vol. 6, Issue 9, ( Part -4) September 2016, pp.13-18
www.ijera.com 13|P a g e
Optimization of Process Parameters And Dielectric Fluids on
Machining En 31 By Using Topsis
A.Hemantha Kumar1
Prof. G. Krishnaiah2
1
Research Scholar, Rayalaseema University /Associate Professor, Mechanical Engineering, AITS, Rajampet
2
Professor, Department Of Mechanical Engineering, AITS, Tirupati.
ABSTRACT
The electric discharge machining is the one of the most desirable machining process for the materials which are
having high hardness and good thermal conductivity. The EDM process surpassed through the technological
barriers by overcoming limitations like processing speed, material conductivity, dimensional accuracy, and
surface finish and so on. However, environmental impact due to release of toxic emissions aerosols during the
process, poor operational safety due to fire hazard, electromagnetic radiation and non-bio degradable waste are
the major problems concerned with conventional dielectric fluids (i.e. kerosene, hydro carbon, etc.,). To reduce
the problems with conventional die electric fluids waste palm oil blended with kerosene is used. The process is
mostly used in situations where intricate, complex shapes need to be machined in very hard materials. The
objective of this work is to study the influence of four design factors current (I), voltage (V), pulse on(P on), and
pulse off(P off) which are the most relevant parameters to be controlled by the EDM process over machining
characteristics such as material removal rate (MRR) characteristics of surface integrity such as average surface
roughness (Ra). Multi Objective optimization of process parameters is done by using TOPSIS.
Keywords: Electric discharge Machining (EDM), Material Removal Rate (MRR), Surface roughness (Ra),
Technique for order of preference by similarity to ideal solution TOPSIS.
I. INTRODUCTION
Electric discharge machining (EDM)
process has gone through considerable changes in
terms of technology and application. Technological
changes were came into existence to meet modern
society needs by easy manufacturing system with
competitive environment to meet customer
requirement with cheap cost and maintaining quality
standards. As the technology goes on increasing
impact on the environment also increasing [1]. The
major changes or improvements were done at the
areas of die electric fluid and process parameter
optimization. EDM processes have gone through
considerable changes in terms of types of dielectric
fluids used and modes of dielectric supply.
Hydrocarbon oils,
Water-based solutions, synthetic and
mineral oil, and gaseous dielectric fluids have been
experimented with wet, powder mixed, dry and
near-dry modes of dielectric supply. EDM process
has expanded its stems into the manufacture of
simple to the most complex geometrical profiles,
meso- to micro-manufacturing, processing of low to
high melting temperature materials, processing of
soft to the hardest materials and generating rough to
mirror finished surface accuracies.
Lazarenko had the idea of exploiting the
destructive effect of electrical discharge and
developed a controlled process for machining
materials that are conductors of electricity. This was
in 1943; erosion by electrical discharges was born.
Researchers [2] observed from the
experimental results that the graphite powder and
surfactant added dielectric fluid significantly
improved the MRR, reduces the surface roughness
(SR), tool wear rate (TWR) and recast layer
thickness (RLT) at various conditions. Presence of
[3] metal partials in dielectric fluid diverts its
properties, which reduces the insulating strength of
the dielectric fluid and increases the spark gap
between the tool and work piece. As a result, the
process becomes more stable and metal removal rate
(MRR) and surface finish increases. The EDM
process is mainly used for making dies, moulds,
parts of aerospace, automotive industry and surgical
components etc. This paper reviews the research
trends in EDM process by using water and powder
mixed dielectric as dielectric fluid. The results
showed that [4] using tap water as dielectric fluid
for machining can obtain high MRR, decrease the
machining cost and have no harmful to the operators
and the environment. The next area of improvement
is process parameters optimization. Material
Removal Rate (MRR), Tool Wear Rate (TWR),
Electrode
Wear Ratio (EWR) and Surface Roughness (SR)
have been investigated using chromium powder
mixed to the dielectric. [5] Analysis of variance
(ANOVA) and F-test were performed to determine
the significant parameters at a 95% confidence
interval. Predicted results have been verified by
confirmatory tests which show an improvement in
RESEARCH ARTICLE OPEN
ACCESS

the preference values using TOPSIS and GRA
respectively.
[6]The parameters were optimized using
multi-objective optimization technique of
desirability approach and the significance of each
parameter was analyzed by Analysis Of Variance
(ANOVA). In addition, Fuzzy Logic Model (FLM)
was used to better understand the input and output
responses. With the desirability approach, it was
sought to optimize the values for copper electrode
for maximum MRR and minimum TWR and SR.
Overall, the rectangular tool geometry emerged
successful. A comparison of the performances of the
electrode by desirability approach and ANOVA
showed that the current was the most influencing
factor, followed by pulse on time and pulse off time.
It was also observed that the rectangular tool
geometry provided better results as compared to
other tool geometries. Validation tests for FLM
were carried out and show closer relationship with
the experimental results. [7] To find out the
combination of process parameters for optimum
surface roughness and material removal rate (MRR)
in electro discharge machining (EDM) of EN31 tool
steel using artificial bee colony (ABC) algorithm.
The process parameters were varied based on central
composite design (CCD). Second order response
equations for MRR and surface roughness are found
out using response surface methodology (RSM). For
optimization, both single and multi-objective
responses (MRR and surface roughness: Ra) are
considered. From ABC analysis, the optimum
combinations of process parameters are obtained
and corresponding values of maximum MRR and
minimum Ra are found out. In the present paper we
were replaced the conventional die electric fluid
with waste palm oil blended with kerosene and
Experiments were carried out based on Taguchi L9
orthogonal array and grey relational analysis, and
then verified the results through a confirmation
experiment.
1.1 WASTE PALM OIL BLENDED WITH
KEROSENE AS DIELECTRIC FLUID
Waste palm oil blended with kerosene was
alternate die electric fluid in EDM. The waste palm
oil pocess some important properties to provide
sustainable and economical machining. It was Eco-
friendly, since it provides very less emissions than
the kerosene. The potential properties of waste palm
oil blended with kerosene to be as a die electric fluid
as given in below.
[1] Higher flash point, excellent biodegradability,
higher oxygen content, Low carbon atom chain,
nontoxic, higher breakdown voltage, higher
viscosity, Lower toxic emissions & lower volatility
and toxic emissions.
Many researches said that waste vegetable oils as
dielectric fluid in EDM had significant performance
by improving sustainability and material removal
rate (M.R.R).
Waste palm oil was blended with kerosene
and sodium dicolus sulphate was used as the
surfactant. Ultra solidification and agitation was
done for proper blending of waste palm oil with
kerosene. The agiator and ultrasonicator were shown
in fig.1.1
Fig.1.1 Agitator and Ultrasonicator
Table 1.1 properties of waste palm oil blended
with kerosene and kerosene based dielectric fluids.
Property Waste palm
oil blended
with
kerosene
Kerosene
Density (gm/ml) 0.845 0.80
Viscosity at (40 °C) 6.56 2.71
Thermal conductivity
(W/m·K)
0.168 0.15
Specific heat (J/kg·K) 1.9 2.01
Flash point (°C) 130 81
BD voltage (kV/2.5 mm) 22 18
Dielectric Constant 3.4 4.7
Some values of the dielectric are taken from
literature.
II. EXPERIMENTATION
2.1 SELECTION OF WORK PIECE
For the present work copper as electrode having
excellent electrical and thermal conductivity. The
properties of the electrode are given in table 2.1.
The work piece material is die steel EN 31 with the
dimension of 120×100×10 mm which is utilized for
manufacturing of various products in our day to day
life. The chemical composition of the work piece as
shown in the below table2.2

Table 2.1. Properties of the Electrode material
used.
Table 2.2 chemical composition of die steel
(EN31)
Composition C Mn Si S P Cr
Percentage 1.07 0.57 0.32 0.04 0.04 1-
1.6
Mechanical properties are
Modulus of Elasticity 197.37 GPa
Yielding Strength 528.97 MPa
Ultimate Tensile Strength 615.4 MPa
In this study, the Die Sinking EDM machine is used
and the experimental setup is shown in Fig. 1. A
copper rod with the diameter of 16 mm and the
height of 70 mm was used as electrode in this study.
In addition, waste palm oil blended with kerosene
was employed as a dielectric fluid in this
investigation. Experimental levels of the machining
parameters are shown in table 2.3
Table 2.3.Experimental levels of the machining
Parameters
Parameter Level 1 Level 2 Level 3
Spark current 4 12 20
Gap voltage 30 50 70
Pulse on 125 175 225
Pulse off 100 150 200
2.2 Design of Experiments:
Taguchi’s Technique was implemented to find the
impact of
Process variables on the EDM performance. For the
conduction of experiments L9 taguchi orthogonal
array was used to complete the runs. The important
input parameters selected are peak current ‘Ip’
(Amp), Pulse on time ‘Pon’(μs), Pulse off time ‘Poff’
and Gap voltage ‘Vg’(V) varying at three levels
based on certain pilot experiments performed for
selection of process parameters. The influence of
input parameters on response variables like MRR
and Ra was given in the table 2.4 for palm oil
blended with kerosene and table 2.5 give kerosene
as die electric fluid.
2.3. CONDUCT OF EXPERIMENTS:
Die steel (EN31) material particulate was using
Copper tool with 16mm diameter and the
ELECTRONICA- ELECTRAPULS PS 50ZNC
(die-sinking type) EDM machine were used. Waste
palm oil blended with kerosene and kerosene are
used as dielectric fluid. External flushing was used
to flush away the eroded materials from the sparking
zone. For a four factors are tackled with a total
number of 9 experiments performed on die sinking
EDM. The calculation of material removal done by
using electronic balance weight machine. This
machine capacity is 1000 gram and accuracy is
0.001 gram. Surface roughness of each hole was
measured by using Taly Surf instrument.
Fig.2.1 Die Sinker EDM Model: PS 50ZN
Table 2.4 For waste palm oil blended with kerosene
as dielectric fluid.
S.No Curre
nt (a)
Volt
age
(v)
Pulse
on(µse
c)
Pulseo
ff(µsec
)
MRR(m
m3
/min)
Ra
(µm)
1 4 30 125 100 12.7388 1.2900
2 4 50 175 150 15.2866 1.2700
3 4 70 225 200 25.4777 1.400
4 12 30 175 200 38.2165 1.3900
5 12 50 225 100 42.0382 1.2533
6 12 70 125 150 40.7643 1.1566
7 20 30 225 150 52.2292 1.7366
8 20 50 125 200 54.7707 1.8966
9 20 70 175 100 63.6942 1.7400
Table 2.5 For kerosene as dielectric fluid.
S.No Curr
ent
(a)
Vol
tag
e
V(v
)
Pulse
on(µs)
Pulseof
f(µs)
MRR(m
m3
/min)
Ra
(µm)
1 4 30 125 100 12.7388 0.8633
2 4 50 175 150 12.9895 0.7966
3 4 70 225 200 13.2278 0.9766
4 12 30 175 200 25.4777 1.7500
5 12 50 225 100 29.0456 2.5100
6 12 70 125 150 33.7621 1.5266
7 20 30 225 150 45.8734 2.9933
8 20 50 125 200 50.1554 2.0433
9 20 70 175 100 63.4042 1.7633
Compositio
n
Density
(gm/cm3
)
Melti
ng
point
Thermal
resistivit
y
Hardnes
s
99.9%
copper
8.904
1083o
C
9cm HB 100

Fig.2.2 Work pieces after machining with waste
palm oil blended with kerosene and kerosene as
dielctric fluids.
Fig.2.3 Measuring of surface roughness by using
taly surf meter.
III. MULTI OBJECTIVE OPTIMIZATION
Technique for order of preference by similarity
to ideal solution (TOPSIS):
TOPSIS is a multi-objective optimization
technique used to determine the most suitable
alternative from a finite set. The principle of the
technique is that the selected criteria should be
nearest from positive best solution and farthest from
negative best solution, the finest solution being the
one having the most relative closeness to the ideal
solution. The steps involved in carrying out TOPSIS
are expressed as:
Step1: Objective Function table consists of MRR &
Ra
Step 2: Determination of normalized matrix.
(8)
Step 3: The weighted normalized decision matrix is
constructed by multiplying the normalized decision
matrix by its associated weights.
Wij = Nij×Wj (9)
Step 4: a) Determine matrix A3 and A4 such that
A3 = A1× A2 and A4= A3/A2,
where A2 =
b) Calculate the maximum Eigen value (λmax),
which is the average of matrix A4.
c) Determine the consistency index
The smaller value of CI the smaller is the
deviation from the consistency. Evaluate the random
index (RI) for the number of attributes used in
decision-making.
Determine the consistency ratio (CR = CI/RI).
Step 5: Determination of the positive ideal solution
(si**) and the negative ideal solution (si*).
si
**
= {(max Wij | j ∈ J ), (min Wij | j∈ J' )} (10)
si* = {(min Wij | j ∈ J ), (max Wij | j∈ J' )} (11)
J = 1, 2, 3,…, n − where J is associated with the
benefit criteria J' = 1, 2, 3,…, n − where J' is
associated with the cost criteria.
Step 6:
The separation measure is calculated. The
separation of each alternative from the positive ideal
one is given by:
Si
**
=Σ(Wij – Aj**
)2
, j = 1,where i = 1, 2,.,m.(12)
Similarly, the separation of each alternative from the
negative ideal one is given by:
Si
*
= Σ(Wij – Aj*
)2
, j = 1, where i = 1, 2,...,m.(13)
Step 7: The relative closeness is calculated to the
ideal solution.
(14)
The larger the value the better is the performance
of the alternatives.
Step 8: Rank the relative closeness value.
For waste palm oil blended with kerosene as
dielectric fluid:

Table 3.1 Rank order for the experiments with
dielectric fluid as Palm oil blended with kerosene.
Experiment No. Preference value Order
1 0.856204248 1
2 0.840291631 2
3 0.725188947 3
4 0.492593032 4
5 0.414311527 6
6 0.433956404 5
7 0.262634554 7
8 0.246349585 8
9 0.139030065 9
Fig. 3.1 Result analysis graph from TOPSIS with
palm oil blended with kerosene as dielectric fluid
Table 3.2 Rank order for the experiments with
dielectric fluid as kerosene.
Experiment No. Preference value Order
1 0.706910041 2
2 0.699407477 3
3 0.716186648 1
4 0.688461418 5
5 0.692663128 4
6 0.544486127 6
7 0.45685107 7
8 0.319088 8
9 0.154700108 9
Fig.3.2 Result analysis graph from TOPSIS with
kerosene as dielectric fluid.
IV. CONCLUSION
The main purpose of our work is to
determine the optimum cutting parameter for
Maximizing the MRR and Minimizing the Ra with
eco-friendly manufacturing.
It is a multi-objective optimization
technique. For this purpose an optimization
technique called TOPSIS (Technique for order of
preference by similarity to ideal solution) is used for
the output responses ie MRR and Ra with process
parameters. And the results are shown in tables 3.1
& 3.2.
 The optimum cutting parameters for palm oil
blended with kerosene as dielectric fluid is
Current 4 A, gap voltage as 30 V, pulse on is
125 µs and pulse off is 100µs
 The optimum cutting parameters with kerosene
as dielectric fluid is Current 4 A, gap voltage
as 70 V, pulse on is 225 µs and pulse off is
200µs
Experiments were conducted by the both
dielectric fluids on the same work piece of die steel
(EN31). And the result shows that machining by
using waste palm oil blended with kerosene give
better results than kerosene as dielectric. It is also
known that emissions such as toxic gases, fumes and
fire accidents are greatly reduced.
Future Scope
EDM is an emerging technology for
providing economical and eco-friendly
manufacturing. There are significant changes in
response characteristics by change of dielectric
fluids. In this paper waste palm oil blended with
kerosene is taken and there is provision to select
waste oil (waste vegetable oils, waste palm oil, etc.)
directly as dielectric medium. Different optimization
techniques are used for getting optimum parameters.
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Effect of dielectric fluid with surfactant and
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