Optimization of MRR and SR by employing Taguchis and ANOVA method in EDM

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
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Optimization of MRR and SR by employing Taguchis and ANOVA
method in EDM
Amardeep Kumar1, Avnish Kumar Panigrahi2
1M.Tech, Research Scholar, Department of Mechanical Engineering, G D Rungta College of Engineering &
Technology, Bhilai, Chhattisgarh (India)
2 Assistant Professor, Department of Mechanical Engineering, G D Rungta College of Engineering & Technology,
Bhilai, Chhattisgarh (India)
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Abstract - The main objective of the present work is to
maximize the Material Removal Rate (MRR) and minimizethe
Surface Roughness (SR) value. Experimentswereperformedby
Yang et al. (2009) on die-sinking machine by using an Electric
Discharge Machine. The process parameters considered in
their experimental work include discharge current (I), source
voltage (V), pulse-on time (Ton) and pulse-off time (Toff). We
have applied the Taguchi’smethodandthereDOEandTaguchi
based ANOVA analysis to optimize the above stated two
process performance factors i.e. MRR and SR. The main results
from the present analytical work are summarized as the most
important parameter with the aspect of MRR is discharge
current (I), as the discharge current (I) showsthecontribution
ratio of the order of 33.33 %. The performance of SR is most
affected by the factor B. The contribution ratios of discharge
current (I) is Re 33.16 % and after that factor C , pulse-on time
(Ton) have 30.62%.
Key Words: MRR, SR, Taguchi Method, ANOVA analysis
1. INTRODUCTION
Traditional Machining,alsoknown“conventional machining”
requires the presence of a tool that is harder than the work
piece to be machined. This tool should be penetrated in the
work piece to a certain depth.
Furthermore, a relative motion between the tool and work
piece is responsible for forming or generating the required
shape of the object. The absence of any elements in any
machining process such as the absence of tool-work piece
contact or relative motion makes the process a non-
traditional or non-conventional one [1].
Electrical Discharge Machining (EDM) is now a well-known
modern manufacturing process, machining process, into
which electrically conductive material is removed via means
of controlled erosion through a series of electric-sparks of
short duration (in micro seconds) and high current density
between the electrode and the work-piece. In this process
(EDM) electrode and the work-piecebotharesubmergedina
dielectric bath, containing kerosene or distilled water [2].
1.1 WORKING MECHANISM OF EDM
As above said that during the EDM process, thousands of
sparks per-second are generated, and each spark produces a
tiny crater in the object material along the cutting path by
melting and vaporization.
The top surface of the work-piece afterward re-solidifies and
cools at a very high rate. Electrical Discharge Machining
(EDM) uses thermal energytoachieveahigh-precisionmetal-
removal process from a fine, precisely, accurate controlled
electrical discharge. The electrode is used to move towards
the work-piece until the gap is small enough so that the
impressed voltage is great enough to ionize the dielectric [1].
Short duration discharges are generated in a liquid dielectric
gap, which separates toolandwork piece (in EDM, thereisno
physical contact between tool and wok-piece) . The material
is removed with the erosive effect of the electrical discharges
from tool and work piece. EDM does not make direct contact
between the electrode and the work piece thus it can
eliminate mechanical stresses, chatter and vibration
problems during machining [3-4].
1.2 WORKING PRINCIPLE OF EDM
In EDM, the machining process is carried out within the
dielectric fluid which creates path for discharge. When
potential difference is applied between these twosurfacesof
work-piece and tool, the dielectric gets ionized and electric
sparks/discharge are generatedacrossthetwoterminals. An
external direct current power supply is connectedacross the
two terminals to create the potential difference.
The polarity between the tool and work-piece can be
exchanged but that will affect the various performance
parameters of EDM process. For extra material removal rate
(MRR) work-piece is connected to positive terminal as two
third of the total heat generated is generated across the
positive terminal. As the work-piece keep on fixed on the
base by the fixture arrangement, the tool helps in focusing
the intensity of generated heat at the place of shape
impartment.
The working and principle componentsofEDM areshown
in below Figure 1.

Fig.1: Working and principle components of EDM
2. NEED FOR OPTIMIZATION IN EDM
Optimization is performing or applied in order to obtain the
best (optimum) desired result under the given specified
experimentalconditions. In any engineeringmachinesystem,
engineers have taken many technological and executive
decisions at various stages.
The most significant objective of the decision is either to
minimize the effort/time required or maximize the desired
results/benefits of the product or advantage in term of
economics.
In EDM, traditional method of selection of parameters
combinations doesnotprovidesatisfactoryordesiredresults.
Optimization of process parameters of EDM has been treated
as single-objective Optimization process and multi-objective
Optimization problem. Designs of experiments (DOE)
techniques like Taguchis method, Response Surface
methodology (RSM) etc. are used to reduce the experimental
runs in actual manner.
3. LITERATURE SURVEY
A review on current research trends in electrical discharge
machining (EDM) presented by[5]. They presented the
research trends in EDM on ultrasonic vibration, dry EDM
machining, EDM with powder additives, EDM in water and
modeling technique in predicting EDM performances.
Bhattacharyya et al. [6] has developed mathematical models
for surface roughness, white layer thickness and surface
crack density based on responsesurfacemethodology(RSM)
approach utilizing experimental data. It emphasizes the
features of the development of comprehensive models for
correlating the interactive and higher-order influences of
major machining parameters i.e. peak current and pulse-on
duration on different aspects of surface integrity of M2 Die
Steel machined through EDM.
Tzeng et al. [7] had proposed an effective process parameter
optimization approach that integrates Taguchi’s parameter
design method, response surface methodology(RSM),a back
propagation neural network (BPNN),anda genetic algorithm
(GA) on engineering optimization concepts to determine
optimal parameter settings of the WEDM process under
consideration of multiple responses. Material removal rate
(MRR) and work-piece surface finish on process parameters
during the manufacture of pure tungsten profiles by wire
electrical discharge machining (WEDM).
Specimens were prepared underdifferent WEDMprocessing
conditions based on a Taguchi orthogonal array (TOA) of 18
experimental runs. The results were utilized to train the
BPNN to predict the material removal rate and roughness
average properties. Tzeng and Chen [8] analysed a hybrid
method including a back-propagation neural network
(BPNN), a genetic algorithm (GA) and response surface
methodology(RSM)todetermineoptimal parametersettings
of the EDM process. The parameters MRR, EWR and work-
piece surface finish (SF) during themanufactureofSKD61 by
electrical discharge machining (EDM) have been optimized.
Muthuramalingam and Mohan [9] found by their
experimental analysis that the current intensity (CI) of the
EDM process affects the material removal rate(MRR)greatly
and they developed Taguchi-DEAR methodology based
optimization of electrical process parameters. Marafona and
Wykes [10] described an investigation into the optimization
of material removal rate (MRR) in the electric discharge
machining (EDM) process with copper tungsten tool
electrode. From the experimental results, it has been proved
that large current intensity would result in higher material
removal rate.Matoorian et al. [11] presented the application
of the Taguchi robust design methods to optimize the
precision and accuracy of the EDM turning process for
machining of precise cylindrical forms on hard and difﬁcult-
to-machine materials.
3.1. Objective of the Present Work
From the above literature review, it was observed or can be
conclude that a lot of work by using the various optimization
techniques (like RSM, GA, BPNN, FEM) have been used in
order to optimization of various parameters Electrical
Discharge Machining (EDM) process and its different
parameters. The Taguchi DOE and ANOVA analysis based
Optimization is theevolutionaryalgorithmswhichwereused
by positively by the various investigators. However, these
both optimization techniques (simultaneously) have not
been used in the optimization of the Electrical Discharge
Machining (EDM) process parameters where the optimal
setting is required for a better performance.
The main objective of the present work is to maximize the
Material Removal Rate (MRR) and minimize the Surface
Roughness (SR) value.
Experiments were performedby [12]ondie-sinkingmachine
by using an Electric Discharge Machine. They applied
Simulated Annealing (SA) optimization method in order to
maximize the MRR and minimize the SR. The process
parameters considered in their experimental work include
discharge current (I), source voltage(V),pulse-ontime(Ton)
and pulse-off time (Toff).

3.2. Control factors and there levels
Four parameters namely: Discharge current (I), Source
voltage (V), Pulse-on time (Ton) and Pulse-offtime(Toff) are
varied alternatively. During the experiments Material
Removal Rate and Roughness Average (Ra) have also been
noted down and given in Table 1.
Table -1: Process parameters and there levels
Input
Parameters/Factors
Symbol Level 1 Level 2 Level 3
Voltage (V) A 80 160 200
Current (I) (A) B 6 16 48
Pulse on time (Ton) (μs) C 6.4 100 800
Pulse off time (Toff) (μs) D 12.8 50 400
Taguchi constructed a special set of general designs for
factorial experiments. The special set of designs or Taguchi
Robust Design method uses a mathematical tool called
orthogonal arrays (OAs) and Signal to Noise ratio (SNR) to
study a large number of experimental process variableswith
a small/reduce number of experiments.
All the experiments and there corresponding values of MRR
and SR are listed in a plan given in Table. 2.
Table -2: Experiments and there corresponding values of
MRR and SR
Experiment
Run No
A
(Volt)
B
(Amp)
C
(μs)
C
(μs)
MRR
Surface
Roughness
1 1 1 1 3 0.2
2.62
2 1 1 3 1 0.3 2.87
3 1 2 1 3 0.3
3.05
4 2 1 3 1 0.2 2.68
5 2 2 2 1 20.4
8.32
6 2 2 3 2 55.1
9.31
7 3 1 3 4 0.3
2.05
8 3 1 3 2 0.3 2.69
9 3 2 2 1 54
10.43
The present Taguchi analysis is per-formed with help of
MINITAB 17.0 software. For analysis we have selected the
present experimental design in OAs L9 with degree of
freedom (DOF) = 8. Four parameters and each of having
three levels selected
3.3. Main effects plot for MRR
Figure 2 depicted the main effect of control factorstermsviz.
factors A, B, C and D on MRR. From the main effect plots, it
has been observed that yield of MRR increases with increase
in Voltage from 80 (V) to 160 (V) but after that its having
decreasing value, MRR having continuous increasing
phenomena when I (A) increases from 6 (A) to 16 (A) and 16
(A) to 48 (A) due to the formation of more non condensable
volatile fractions by severe cracking at higher temperature
MRR having increasing trend with pulse on Time (Ton) upto
100 (μs) and after that it starts decreasing.
It (MRR) when increases the Ton from 6.4 to 100 (μs) it
happens due to the fact that because the discharge energy
increases with the Ton upto certain value and peak current
leading to a faster cutting rate.
Furthermore MRR having first increasing trend when pulse
off Time increase from 12.8 to 50 and after that it having
reducing values with increasing further value of Toff 50 to
400 (μs)
Fig.2: Main effect plots of different factors on MRR
3.4. Analysis of SN Ratio for MRR
Figure 3 shows the main effect plots of SN ratio of different
actors terms viz. factors A, B C and D on MRR.
Here we select the options for larger or ‘Higher is better
(HB)’.It is observed from this Fig.3. and Table .3, that MRR
have highest SN ratio for Voltage (V) at the level 2,butforthe
case of I (A) it is having highest for the third level. Similarly
MRR have optimal value for pulse on Time (Ton) at 100 (μs)
and for pulse off Time (Toff) at 50 (μs)

Fig.3: SN ratio plots of different factors effects on MRR
Table.3. Response Table for SN ratios of MRR
Response Table for Signal to Noise Ratios
Larger is better
Level A B C D
1 -11.6315 11.8663 11.6315 9.1447
2 15.6787 7.8675 30.5078 12.0952
3 4.5776 34.7355 -0.0617 -11.6315
Delta 27.3103 46.6018 42.1393 23.7267
Rank 3 1 2 4
4. ANALYSIS OF VARIANCE (ANOVA) ANALYSIS FOR
MRR
After performing the Design of Experiments (DOE)
performance, it isnecessarytoperformANOVAwhich,comes
under the Taguchi Grey (TG) method. Analysis of variance
(ANOVA) performed after evaluating DOE analysis to
establish the optimal geometric and flow parameters. The
present ANOVA is performed withtheconfidenceof90%and
the significance level (or error level of) 10%.
The overall of or cumulative of all factors ANOVA analysis
have been performed and reported on the Table 4.10.
The ANOVA analysis in Table 4. indicate that source voltage
(V), discharge current (I), pulse-on time (Ton) and pulse-off
time (Toff) influence the contribution performance values
with 19.53 %, 33.33 %, 30.14 % and 16.97 %, respectively.
The contribution percentage of each factor on MRR is also
tabulated in Table 4.
Table.4. Analysis of Variance for All factors collectively SN
Ration for MRR
ANOVA: MRR versus Factors A,B,C and D
Source DF Adj SS Adj MS F-Value P-Value
Contribution
Percentage
(%)
A 1 27.37 27.37 1.25 0.326 19.53
B 1 2564.66 2564.66 117.09 0.000 33.33
C 1 37.45 37.45 1.71 0.261 30.14
D 1 84.90 84.90 3.88 0.120 16.97
Error 4 87.62 21.90
Total 8 4458.92
Model Summery
S R-sq. R-sq. (adj)
4.68017 98.04% 96.07%
At the last model summery table have also been presented
which shows the 98.04 % of R2 which shows the accuracy of
the present model results.
4.1. OPTIMIZATIONOFTHEPRESENTRESULTSFOR
MRR
The analysis of the results gives the combination factors
resulting in maximum MRR among the investigated
experimental configurations are A = 160 V (A2), B = 48 A
(B3), C = 100 μs (C2) and D = 50 μs (D3). Consequently,
A2B3C2D2 is defined as the optimum condition of design
parameters related to the MRR according to the “HB”
situation.
The optimization has been performed corresponding to
Maximum MRR with following subjected constraintswithits
minimum and maximum value. Optimization has been
performed with the confidence of 90% and the error level of
10%.
The below Figure 4. indicate that the optimizedvalueofMRR
value is obtained as = 58.67 (mm3/min) or (g/h) while as

per Yang et al. analysis by employing SA (simulated
annealing) Algorithm it comes54.93whichshowsthe6.37%
deviation from their results while they appliedthesimulated
annealing (SA) optimization method for L15.
Fig. 4: Optimization of the present result for MRR.
In the present analysis the optimization of different
controlling factorstowardstheMRR hasalsobeenoptimized,
in order to the analysis has been performed.
The Figure 5 indicate that the optimized values of different
factors, which is (optimized value) obtained as for factor
A = 134.20, for factor B = 7.00, for factor C = 374.79, while
for factor D is obtained as D = 200.63.
Fig. 5: Optimization of the Different factors.
4.5. MAIN EFFECTS PLOT FOR SURFACE
ROUGHNESS
Figure 6 depicted the main effect of control factorstermsviz.
factors A, B, C and D on SR. From the main effect plots, it has
been observed that yield of SR increases with increase in
Voltage from 80 (V) to 160 (V) but after that it decreases
when we switch the value of V from 160 to 200, for thefactor
B, SR having all increasing trends for all values of I (A) .
Fig.6: Main effect plots of different factors on Surface
Roughness (SR)
SR having first increasing and after that decreasing trend
with pulse on Time (Ton). It (SR) when increases the Ton
from 6.4 to 100 (μs) and after that it decreases 100 to 800
(μs), Furthermore SR having decreasingtrendwhenpulse off
Time increase from 50 to 400 (μs).
4.5.1. Main Effects Plot for SN ratios
After implementing the numerical simulations, based on the
prescribed Taguchi Orthogonal Array of Table 4.13, the
results are transformed into signal-to-noise ratio (SNR).
Figure7 shows the main effect plots of SN ratio of different
actors terms viz. factors A, B C and D on MRR. Here we select
the options for “Smaller is better (SB)”.

Fig .7: SNR plots of different factors on SR
4.5.2. Contribution Ratio of each factor for SR
The below Fig.ure8 indicate that the Source current (I)
(Factor B), have the highestaffectingparametersonSRwhich
is 33.16 % contribution among theall.Itisalsoobservedfrom
the table that the Pulse on time (Ton) i.e. factor C , is the
second most significant factor among all factors as it shows
30.62 % contribution towards SR.
While factor D = 18.11%affectingtheSRvalues.Furthermore
source voltage (V) has least contribution significance on the
SR values at showing 18.09 %.
Fig.8: Contribution Ratio of each parameter to SR
4.5.3. Validation of Optimal combination of control
factors for SR
The below Figure 9 indicate that the optimized value of SR
value is obtained as = 5.04(μm) while as per Yang et al. itwas
reported 2.07, while they have applied the simulated
annealing (SA) optimization method.
Fig. 9: Optimization of present results for factor SR
4.6. PROBABLE OPTIMUM DESIGNS CONDITIONS
FOR MAXIMIZING THE MRR
Based on the above Taguchis DOE and ANOVA analysis
the optimal experimental factors which having
maximum MRRandminimumSRistabulatedinTable5
for MRR and for SR in Table 6
Table 5. Optimum designs conditionsformaximizing the
MRR
Parameters
Optimum
Value
(Present
Analysis)
Optimum
Value
(Yang et al.
(2009)
Factors A B C D MRR (mm3/min)
Optimum
level
A-
2
B-3 C-2 D-2
58.67 54.93
Optimum
Value
16
0
48 100 50
Table 6. Probable optimum designs minimizing the SR
Parameters
Optimum
Value
(Present
Analysis)
Optimum
Value [12]
Factors A B C
D
SR (μm)
Optimum
level
A-2 B-3 C-2 D-2
5.04 2.07
Optimum
Value
160 48 100 50

4.7. CONCLUSIONS
The present analytical study has been performed in order to
find, the optimal parameters and system designed to
maximize the Material Removal Rate and minimize the
Surface Roughness from thecontrollingfactorsbyemploying
Taguchi DOE method in details. The four different affecting
(experimental) factors and two desired parameters have
been analysed and selected. The desired factors are; MRR
and SR in die-sinking EDM. The influence factors are chosen
as discharge current (I), source voltage (V), pulse-on time
(Ton) and pulse-off time (Toff). ANOVA analysis and their
response and SNR table has been presented. Finally
optimized parameters have also been investigated for both
factors i.e. MRR and SR. The main results from the present
analytical work are summarized as follows:
1. The most important parameter with the aspect of MRR is
discharge current (I), as the discharge current (I) shows the
contribution ratio of the order of 33.33 %.
By the analysis it is found that MRR can be improved by
controlled change of discharge current (I). Optimum
condition of design parameters is A2B3C2D2 and the
optimum values of the parameters for maximum heat
transfer condition are given as follows: A = 134.20, for factor
B = 7.00, for factor C = 374.79, while for factor D is obtained
as D = 200.63.
2. The performance of SR is most affectedbythefactorB. The
contribution ratios of discharge current(I)isRe33.16% and
after that factor C , pulse-on time (Ton) have 30.62%.
The optimum condition of design parameters is A2B3C2D2
and the optimum values of the SR is obtained as 5.04 (μm).
3. From the present analysis Optimized valueofMRRvalueis
obtained as = 58.67 (mm3/min) which shows the 6.37 %
deviation from Yang et al. (2009).
4. The results show that in order to optimize the MRRandSR
there is no need to perform all 81 experiments (34 = 81).
Because performing all the experiments consume too much
time and is not appropriate with respect to the experimental
cost.
Therefore, the Taguchi method was successfully applied to
the present work, with a very limited run number of
experiments and with short span of time.
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