Optimization of Process Parameters for CNC Turning using Taguchi Methods for EN8 Alloy Steel with Coated/Uncoated Tool Inserts

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 180
Optimization of Process Parameters for CNC Turning using Taguchi
Methods for EN8 Alloy Steel with Coated/Uncoated Tool Inserts
Rahul R. Deshpande1, Reena Pant2
1P.G. Student, Department of Mechanical Engineering, 2Bharti Vidyapeeth College of Engineering,
Kharghar ,Navi Mumbai, Maharashtra, India.
2Associate Professor in Mechanical Engineering Department, 2Bharti Vidyapeeth College of Engineering,
Kharghar ,Navi Mumbai, Maharashtra, India.
------------------------------------------------------------***-----------------------------------------------------------
Abstract—Coated and uncoated tool inserts offers certain
degrees of control on desired rate of Tool Wear and surface
roughness to an extent. Significant input parameters are
selected in order to get influence on the response variables.
Experiments were conducted on specimens of EN8 alloy steel
material with the help of PVD coated TiALN insert and
uncoated carbide insert. The experimental analysis is based
on Taguchi method. Taguchi method has become
increasingly popular in recent years. It involves both
experimental design and analysis aspects. Taguchi methods
employ special fractional experiment design called
orthogonal array. Notation of orthogonal array is La where
“ L” is symbol for orthogonal array, “a” stands for the number
of experiments required for this array. Taguchi methods (For
the data analysis, Statistical Techniques of ANOVA was used)
are performed find out significant parameters. Optimization
of process parameters is carried out by Grey Relational
Analysis method. GRA method is powerful and most versatile
tool which can manipulate the input data as per requirement
and comes with results that can be used to have best multi
performance in response concerns.
Keywords—Coated and uncoated tool inserts, Surface
roughness, Material removal rate, ANOVA, Grey
relational analysis.
1. INTRODUCTION
Optimization is one of the effective techniques used in
manufacturing sectors to arrive at the best
manufacturing conditions, which is an essential need for
industries towards manufacturing of quality products at
lower cost .
The Taguchi method involves reducing the variation in a
process through robust design of experiments. The overall
objective of the method is to produce high quality of
product at low cost to the manufacturer. The Taguchi
method was developed by Genichi Taguchi. He developed
method for designing experiments to investigate how
different parameters affect the mean and variance of a
process performance characteristic that defines how well
the process is functioning. The experimental design
proposed by Taguchi involves using orthogonal arrays to
organize the parameters affecting the process and the
levels at which they should be varied.
Surface roughness is an indicator of surface quality and
is one of the most specified customer requirements in a
machining process. For efficient use of machine tools,
optimum cutting parameters (speed, feed, depth of cut)
are required. So it is necessary to find a suitable
optimization method which can find optimum values of
cutting parameters for minimizing surface roughness. In
modern industry, the goal is to manufacture low – cost
high quality products with maximum productivity in a
short time. Turning is the most common method for
cutting and especially for the finishing of machined
parts. Furthermore, in order to produce with desired
quality and maximum productivity of machining, cutting
parameters selected properly. In turning process,
parameters such as materials, tools geometry and
cutting conditions (depth of cut, feed rate, cutting speed)
have impact on material removal rate and the machining
qualities like surface roughness.
Analysis of variance is a hypothesis – testing
technique used to test the equality of two or more
population means by examining the variances of
samples that are taken . ANOVA allows one to
determine whether the differences between the
samples are simply due to random error or whether
there are systematic treatment effects that causes
the mean in one group to differ from the mean in
another . ANOVA is based on comparing the variance
between the data samples to variation within each
particular sample . If the between variation is much
larger than the within variation , the means of
difference samples will not be equal . If the between
and within variation are approximately the same
size, then there will be no significant difference
between samples means .
J. S. Senthilkumaar et al [1] heat-resistant super alloy
material like Inconel 718 machining is challenging task
even in modern manufacturing processes. Therefore the
genetic algorithm coupled with artificial neural network
(ANN) as an intelligent optimization technique for

machining parameters optimization of Inconel 718. The
combined effects of cutting speed, feed, and depth of cut on
the performance measures of surface roughness and flank
wear were investigated by the analysis of variance.
Radhakrishnan Ramanujam et al [2] investigation of
turning on Aluminium Silicon Carbide particulate metal
matrix composite (Al-SiC–MMC) using polycrystalline
diamond (PCD) 1600 grade insert. Analysis of variance is
used to investigate the machining characteristics of metal
matrix composite (A356/10/SiCP). The objective was to
establish a correlation between cutting speed, feed and
depth of cut to the specific power and surface finish on the
work piece. Analysis of Variance is a method of
apportioning variability of an output to various inputs. The
purpose of the analysis of variance is to investigate which
machining parameters significantly affect the performance
characteristic.
Chinnasamy Natarajan et al [3] surface roughness is an
indicator of surface quality and is one of the most-specified
customer requirements in a machining process. For
efficient use of machine tools, optimum cutting parameters
(speed, feed, and depth of cut) are required. So it is
necessary to find a suitable optimization method which can
find optimum values of cutting parameters for minimizing
surface roughness. In this work, machining process has
been carried out on brass C26000 material in dry cutting
condition in a CNC turning machine and surface roughness
has been measured using surface roughness tester. To
predict the surface roughness, an ANN model has been
designed through feed-forward back-propagation network
using “Matlab” software for the data obtained. Comparison
of the experimental data and ANN results show that there is
no significant difference and ANN has been used
confidently. The results obtained conclude that ANN is
reliable and accurate for predicting the values.
S. Rajesh et al [4] presents the findings of an experimental
investigation into the effects of cutting speed, feed rate,
depth of cut, and nose radius in CNC turning operation
performed on red mud-based aluminum metal matrix
composites and investigates optimization design of a
turning process performed on red mud-based aluminum
metal matrix composites. The major performance
characteristics selected to evaluate the process are surface
roughness, power consumption, and vibration, and the
corresponding turning parameters are cutting speed, feed,
depth of cut, and nose radius.
Tian-Syung Lan et al [5] surface roughness, tool wear, and
material removal rate are major intentions in the modern
computer numerical controlled machining industry.
Through the machining results of the CNC lathe, it was
shows that both tool wear ratio and MRR from our
optimum competitive parameters are greatly advanced
with a minor decrease in the surface roughness in
comparison to those of benchmark parameters. Surface
roughness, tool life, and cutting force are commonly
considered as manufacturing goals for turning
operations in many of the existing research studies. It is
also recognized that lighter cutting force often results in
better surface roughness and tool life.
Lakhdar Bouzid et al [6] in modern industry, the goal is
to manufacture low-cost, high quality products with
maximum productivity in a short time. Turning is the
most common method for cutting and especially for the
finishing of machined parts. Furthermore, in order to
produce with desired quality and maximum productivity
of machining, cutting parameters selected properly. In
turning process, parameters such as materials, tool’s
geometry and cutting conditions (depth of cut, feed rate,
cutting speed) have impact on the material removal rate
and the machining qualities like the surface roughness.
Usually, roughness is taken as a good criterion for a
mechanical component performance and to appraise
production cost, while material removal rate can be
defined as the volume of material removed divided by
the machining time. Another way to define MRR is to
imagine an "instantaneous" material removal rate as the
rate at which the cross-section area of material being
removed moves through the workpiece.
P. Jayaraman et al [7] have used grey relational analysis
to perform multi-objective optimization of surface
roughness, roundness and MRR in turning of AA6063 T6
Aluminium Alloy and determined that cutting speed is
the most influencing parameter affecting combined grey
relational grade followed by depth of cut and feed rate. A
grey relational grade is determined from the grey
analysis. Optimum levels of parameters have been
identified based on the values of grey relational grade
and then the significant contribution of parameters is
determined by ANOVA.
Shreemoy Kumar Nayak et al [8] was investigated the
influence of different machining parameters such as
cutting speed (Vc), feed (f) and depth of cut (t) on
different performance measures during dry turning of
AISI 304 austenitic stainless steel. ISO P30 grade
uncoated cemented carbide inserts was used as a cutting
tool for turning. Three important characteristics of
machinability such as material removal rate, cutting
force (Fc) and surface roughness was measured.
Anders Nordgren et al [9] the plastic deformation of
tools is one of the most important wear modes in metal
cutting. Such deformation changes the geometry of the
cutting edge, which often results in accelerated tool
wear, increased cutting forces, risk of tool failure,
vibrations and poor dimensional accuracy and surface
finishes.

S.J. Raykar et al [10] the high-speed turning is emerging as
a key manufacturing technology in aerospace industry.
High-speed turning is generally performed on the order of
five to ten times the conventional cutting speed. It has
several advantages such as reduction in cutting forces and
temperature, low power consumption, improvement in
surface finish, low stress components, burr-free surfaces,
better dimensional accuracy, and better part quality.
V. Bushlya et al [11] presents results of superalloy
machinability study with uncoated and coated PCBN tools
aiming on increased speed and efficiency. Aspects of tool
life, tool wear and surface integrity were studied. It was
found that protective function of the coating, increasing
tool life up to 20%, is limited to low cutting speed range.
Harsh Y Valera et al [12] study of power consumption and
roughness characteristics of surface generated in turning
operation of EN-31 alloy steel with TiN+Al2O3+TiCN coated
tungsten carbide tool under different cutting parameters.
The study shows the influences of three cutting parameters
like spindle speed, depth of cut and feed rate affecting
surface roughness as well as power consumption while
turning operation of EN-31 alloy steel. Coating is also used
on cutting tools to provide improved lubrication at the
tool/chip and tool/work piece interfaces and to reduce
friction, and to reduce the temperatures at the cutting edge.
During machining, coated carbide tools ensure higher wear
resistance, lower heat generation and lower cutting forces,
thus enabling them to perform better at higher cutting
conditions than their uncoated counterparts.
S. Jadhav et al [13] have used grey relational analysis to
perform multi-objective optimization of surface roughness
& MRR in turning of EN24 alloy steel with coated /uncoated
tool inserts. From , it is concluded that spindle speed &
depth of cut are prominent factors which affect the turning
of EN24 alloy steel. Optimum level of parameters has been
identified based on the values of grey relational grade &
then the significant contribution of parameters is
determined by ANOVA.
2. EXPERIMENTAL DETAILS
EN8 is a medium-carbon low-alloy steel and finds its typical
applications in the manufacturing of automobile and
machine tool parts. Properties of EN8 steel, like low specific
heat, and tendency to strain-harden and diffuse between
tool and work material, give rise to certain problems in its
machining such as large cutting forces, high cutting-tool
temperatures, poor surface finish and built-up-edge
formation. This material have wide range of applications
such as General purpose axles, shafts, gears, bolts and
studs, spindles, automotive and general engineering
components etc.
For experimental study, EN 8 alloy steel material was
taken of size 32 mm diameter and 60 mm length work
piece as shown in figure 1.
Fig. 1: EN8 workpiece
The machining of EN 8 alloy steel was done under dry
cutting condition with the help of coated and uncoated
inserts. Selection of inserts was done with the help of
manufacturing catalogue and finally selected inserts are
PVD coated TiAlN insert and uncoated carbide insert for
general turning having geometry WNMG 12 04 08 as
shown in figure 2.
Fig. 2: PVD coated TiAlN and uncoated carbide insert
Spindle speed, feed and depth of cut are the three cutting
parameters taken for consideration for investigating the
effect on response variables i.e. surface roughness and
material removal rate. Surface roughness was measured
with the help of Handysurf E-35 B surface roughness
tester and material removal rate calculated by
mathematical equation;
MRR = 1000×Vc ×f ×d cut mm3/min
Where, ‘Vc’ is cutting speed in m/min. ‘f ’ is feed rate in
mm/rev. and ‘d cut’ depth of cut in mm.
Pilot experimentation was done to find out the levels of
the cutting parameters. Precut of 0.5 mm depth of cut
was performed on each workpiece before actual turning
in order to remove the rust layer or hardened top layer
from the outside surface. Final levels are shown in table
1.

Factors
Level
1
Level
2
Level
2
Spindle speed (rpm) 1400 1600 1800
Feed (mm/rev.) 0.10 0.15 0.20
Depth of cut (mm) 0.8 1.0 1.2
Table 1 – Final Levels
3. EXPERIMENTAL WORK
Three factors, three levels and nine experiments are taken
in consideration according to Taguchi approach with the
help of “MINITAB 17” software. Experimentation is carried
out according to the L9 orthogonal array for each insert
individually. Precut of 0.5 mm depth of cut was performed
before actual trail on each work piece up to the length 35
mm in order to remove the rust layer. Table 2 shows the
surface roughness values and material removal rate
obtained during experimentation for coated and uncoated
inserts. Figure 3 shows the samples after actual
experimentation. The samples A, B, C...I stands for the
Experiments 1, 2, 3…9 respectively as shown in figure3.
Fig. 3: Turned samples during final experimentation
Ex
.
No
.
N
(rpm)
F
(m
m/r
ev.)
dcu
t
(mm)
Coate
d
insert
Unco
ated
Inser
t
MRR
Ra Ra
1 1400
0.1
0
0.8 1.49 1.52 10907.98
2 1400
0.1
5
1.0 1.54 1.62 20452.46
3 1400
0.2
0
1.2 1.66 1.73 32723.94
4 1600
0.1
0
1.0 1.24 1.30 15582.83
5 1600
0.1
5
1.2 1.12 1.18 28049.09
6 1600
0.2
0
0.8 1.48 1.57 24932.53
7 1800
0.1
0
1.2 0.74 0.94 21036.82
8 1800
0.1
5
0.8 0.96 1.28 21036.82
9 1800
0.2
0
1.0 1.43 1.66 35061.32
Table.2: Experimental results for Ra and MRR for
coated and uncoated inserts
Fig. 4: Graphical representation of surface roughness
with coated/uncoated inserts
Figure 4 shows the variation of surface roughness for
coated and uncoated insert at different cutting
conditions. General tendency is that coated and
uncoated insert gives close to similar surface roughness
values up to the speed 1600 rpm and after that the
difference in surface roughness goes on increasing.
Lower value of surface roughness is obtained at
experiment no. 7 i.e. for coated insert it is 0.74 and for
uncoated insert it is 0.94. Higher value of surface
roughness is obtained at experiment no. 3 i.e. for coated
insert it is 1.66 and for uncoated insert it is 1.73. At 1800
rpm speed the maximum difference occurred in surface
roughness for coated and uncoated insert as shown in
figure 4. From experimental study it is conclude that
coated insert provides better results at dry cutting
condition over the uncoated insert.
4. MULTI-OBJECTIVE OPTIMIZATION BY GREY
RELATIONAL ANALYSIS (GRA)
Grey relational grade is employ to convert multi
objective problem into a single objective. The scope of
this study is to identify the optimal combination of
process parameters that concurrently minimize the
surface roughness and maximize the material removal
rate. In grey relational analysis, the first step is data pre-
processing. This avoids the problem of different scales,
units and targets [13]. The following steps are in GRA:

 Experimental data will be normalize in the range
between zero and one.
 Next, the grey relational coefficient is calculate from
the normalized experimental data to express the
relationship between the ideal (best) and the actual
experimental data.
 Grey relational grade is then computed by averaging
the weighted grey relational coefficients
corresponding to each performance characteristic.
 Statistical analysis of variance is performed for the
input parameters with the GRG and the parameters
significantly affecting the process are found out.
 Optimal levels of process parameters are then choose.
A confirmatory test will be done to support the
findings and an improvement in grey relational grade
[13].
4.1 GRA for coated insert
Step 1: Normalization:
The first step in grey relational analysis is normalization
and which is performed to prepare raw data for the
analysis where the original sequence is transferred to a
comparable sequence. Normalization of response variables
is done in the range between zero and one. The indication
of better performance in turning process for surface
roughness is “Lower the better” whereas it is “Higher the
better” for material removal rate. In grey relation analysis,
for “Lower is better” response normalizing done by
equation (1) and when the response is “Higher the
better”,normalizing done by equation (2).
Smaller is better i.e. for surface roughness
( )
( ) ( )
( ) ( )
( )
For Expt. 1;
( )
( )
Larger is better i.e. For material removal rate;
( )
( ) ( )
( ) ( )
( )
( )
( )
Where ( ) and ( ) are the normalized data and
observed data respectively, for ith experiment using kth
response. The smallest and largest values of ( )in the kth
response are minxi(k) and maxxi (k) respectively. The
normalized values are shown in table 3.
Expt.
No.
Ra
(μm)
MRR
(mm3
/min)
Normalized
Ra MRR
1. 1.49 10907.98 0.18478 0.00000
2. 1.54 20452.46 0.13043 0.39516
3. 1.66 32723.94 0.00000 0.90323
4. 1.24 15582.83 0.45652 0.19355
5. 1.12 28049.09 0.58696 0.70968
6. 1.48
24932.53
0.19565
0.58065
7. 0.74
21036.82
1.00000 0.41936
8. 0.96 21036.82 0.76087 0.41936
9. 1.43 35061.32 0.25000
1.00000
Table.3: Comparability sequence after normalization
Step 2: Determination of deviation sequence:
The deviation sequence Δ0i (k) is the absolute difference
between the reference sequence ( ) and the
comparability sequence ( ) after normalization.
Mathematically it is denoted by;
Δ0I (k)=| ( )- ( )|……………………..(3)
Δ0i(k)=| |
= 0.81522
For MRR;
Δ0i(k)=|
= 1
Step 3: Determination of grey relational coefficient:
The grey relation coefficient ( ) for the kth response
characteristics in the ith experiment can be expressed as;
( )
( )
………………. (4)
Where ∆min is the smallest value of ∆oi(k) = mini
mink|x0*(k)− xi*(k)| and ∆max is the largest value of
∆oi(k) = maxi maxk|x0*(k)− xi*(k)|, x0∗(k) denotes
reference sequence and xi∗(k)denotes the comparability
sequence and is the distinguishing coefficient. The
value of can be adjusted with the systematic actual
need and defined in the range between 0 and 1.
For Surface roughness;
( )
( )

Where ( ) ( ) | | and ∆
max||x0∗(k) − x∗(k)|| = ||1 − 0|| = 1
Where; ζ = distinguishing coefficient between [0, 1] = (0.5)
selected.
( )
( )
For MRR;
( )
( )
Step 4: Determination of grey relational grade:
The overall evaluation of the multi-performance
characteristics is based on the grey relational grade and it
is defined as an average sum of the grey relational
coefficients which is defined as follows;
∑ ( ) …………… ( 5 )
Where is grey relational grade; n is the number of
performance characteristics. Influence of the response
variables can be controlled by deciding the optimum
machining parameters varying the value of w keeping in
mind ∑ should be equal to 1. The GRC and
corresponding GRG for each experiment for turning
operation are calculated. The value of GRG is near to the
product quality for optimum process parameters.
GRG ( ) for first experiment calculated as:
(0.5 )
(Bold number indicates higher grey relational grade in table 4)
E
x.
N
o.
Deviation Seq.
GRC GRG
Ra MRR Ra MRR w1=w2=0.5
1
0.81522
1.0000
0
0.3801
7
0.33333 0.3567
2 0.86957
0.6048
4
0.3650
8
0.45255 0.4088
3 1.00000
0.0967
7
0.3333
3
0.83784 0.5856
4 0.54348
0.8064
5
0.4791
7
0.38272 0.4309
5 0.41304
0.2903
2
0.5476
2
0.63265 0.5901
6 0.80435
0.4193
5
0.3833
3
0.54386 0.4636
7 0.00000
0.5806
4
1.0000
0
0.46269 0.7313
8 0.23913
0.5806
4
0.6764
7
0.46269 0.5696
9 0.75000
0.0000
0
0.4000
0
1.00000 0.7000
Table.4: Deviation sequence, grey relational coefficient
and grey relational grades
Average mean of GRG (ᵞm) =Total sum of
grades / 9
= 0.5374
Step 5: Determination of optimal parameters:
The grey relational grade calculated for each sequence
(as shown in table 4) is taken as a response for the
further analysis. The larger-the better quality
characteristic was used for analyzing the GRG, since a
larger value indicates the better performance of the
process. The response table of Taguchi method is
employed here to calculate the average grey relational
grade for each factor level (Table 5)
Level Spindle speed Feed Depth of cut
1 0.4504 0.5063 0.4633
2 0.4949 0.5228 0.5132
3 0.6670* 0.5831* 0.6357*
Delta 0.2166 0.0768 0.1724
Rank 1 3 2
Table.5: Response table for GRG
Table 6: ANOVA for GRG (multiple response
characteristics
Source
DF
seq SS Adj MS F P
%
contri
butio
n
Spindle
speed
2 0.078514
0.039257
120.7
5
0.00
8
57.66
Feed 2 0.009795
0.004897 15.06
0.06
2
7.19
Depth of
cut
2 0.047194
0.023597 72.58
0.01
4
34.66
0.000650 0.000325
total 8
Error 2
0. 136152

Fig. 5: Main effects plot for Means for GRG
Figure 5 shows the finest combination values for
maximizing the multi-objective characteristics or grey
relational grade were spindle speed of 1800 rpm, feed rate
of 0.2 mm/rev. and depth of cut of 1.2 mm. The response
table for the means of grey relational grade is shown in
table 5. The ANOVA output of the multi-objective
characteristics is given in table 6. From the analysis of this
table, it is concluded that spindle speed (57.66 %
contribution) followed by feed and depth of cut, is the most
significantly affecting the grey relational grade.
Step 6: Confirmatory experiment:
Once the optimum level of machining parameters is
selected then the final step is to predict and verify the
improvement of the performance characteristics using the
optimum level of the machining parameters. The estimated
or predicted GRG (ᵞpredicted) at the optimum level of the
machining parameter can be calculated by equation (6).
ᵞpredicted= ᵞm+∑q i=1 ᵞi − ᵞm) ………….(6)
Where ᵞm is the total mean of the grey relational grade ᵞi is
the mean of GRG at the optimum level of ith parameter, and
q is the number of machining parameters that significantly
affect GRG. Results are shown in table 7.
From equation (6),
ᵞpredicted= 0.5374 + [(0.6670 ‒ 0.5374) + (0.5831 ‒
0.5374)+ (0.6357‒ 0.5374)]
= ᵞpredicted = 0.8107
Factors
Optimum
by grey
analysis
N3
f1
dcut3
Optimum cutting
parameters
Prediction
N3
f3
dcut3
Experiment
N3
f3
dcut3
Ra(µm) 0.74 0.98
MRR(mm3/
min)
21036.82 42072.20
GRG 0.7313 0.8107 0.8554
Table.7: Results of confirmation experiment for GRG
Improvement in GRG = 0.8554 - 0.7313
= 0.1241
%error=100- (Predicted GRG / Experimental GRG) × 100
= 100 - (0.8107 / 0.8554) × 100
= 5.23 %
4.2 GRA for uncoated insert
Similar procedure carried out for the uncoated
insert and it results are shown in table 8, 9, 10, 11 and
12 respectively;
Table 8: Comparability Sequence after normalization
Ex
No
0 GRC GRG
Ra MRR Ra MRR
w1=w2
=0.5
1 0.73418 1.00000
0.4051
3
0.33333 0.3692
2 0.86076 0.60484
0.3674
4
0.45255 0.4100
3 1.00000 0.09677
0.3333
3
0.83784 0.5856
Expt.
No.
Ra
(μm)
MRR
(mm3
/min)
Normalized
Ra MRR
1. 1.52 10907.98 0.26582 0.00000
2. 1.62 20452.46 0.13924 0.39516
3. 1.73 32723.94 0.00000 0.90323
4. 1.30 15582.83 0.54430 0.19355
5. 1.18 28049.09 0.69620 0.70968
6. 1.57
24932.53
0.20253
0.58065
7. 0.94
21036.82
1.00000 0.41936
8. 1.28 21036.82 0.56992 0.41936
9. 1.66 35061.32 0.08861
1.00000

4 0.45570 0.80645
0.5231
8
0.38272 0.4529
5 0.30380 0.29032
0.6220
5
0.63265 0.6274
6 0.79747 0.41935
0.3853
7
0.54386 0.4646
7 0.00000 0.58064
1.0000
0
0.46269 0.7313
8 0.43038 0.58064
0.5374
1
0.46269 0.5001
9 0.91139 0.00000
0.3542
6
1.00000 0.6771
Table.9: Deviation sequence, grey relational
coefficient and grey relational grades
Sour
ce
D
F
Seq
SS
Adj MS F P
%
Co
Contributi
on
Spind
le
speed
2
0.
051139
0
0..025
569
16.8
1
0.
0
56
40 40.63
Feed
2
0.00979
5
0.0036
95
2.43
0
0.
2
92
5.8 5.87
D
Dept
h of
cut
2
0.06428
0
0.0321
4
21.1
3
0.
0
45
3 51.07
Error
2
0.00304
2
0.0003
25
total
8
0
0.12585
2
Table.11: ANOVA for GRG (multiple response
characteristics)
Fig. 6 :Main effects plot for Means for GRG
Figure 6 shows the finest combination values for
maximizing the multi-objective characteristics or grey
relational grade were spindle speed of 1800 rpm, feed
rate of 0.2 mm/rev. and depth of cut of 1.2 mm. The
response table for the means of grey relational grade is
shown in table 10. The ANOVA output of the multi-
objective characteristics is given in table 11. From the
analysis of this table, it is concluded that depth of cut
(51.07 % contribution) followed by speed and feed, is
the most significantly affecting the grey relational grade.
Factors
Optimum
by gGrey
analysis
N3
f1
dcut3
Optimum cutting parameters
Prediction
N3
f3
dcut3
Experiment
N3
f3
dcut3
Ra 0.74 0.98
MRR 21036.82 42072.20
GRG 0.7313 0.7895 0.8224
Table.12: Results of confirmation experiment for GRG
Improvement in GRG = 0.8224 – 0.7313 = 0.0911
Percentage error = 100 - (Predicted GRG /
Experimental GRG) × 100
= 100 - (0.7895 / 0.8224) × 100
=4.01 %
5. CONCLUSIONS
The surface roughness and material removal rate were
measured under dry cutting condition for different
combinations of machining parameters for both the
coated and uncoated inserts separately. The final
conclusions arrived, at the end of this work are as
follows:
Table.10: Response table for GRG

 From GRA, it is concluded that spindle speed and
depth of cut are prominent factors which affect the
turning of EN8 alloy steel. For coated insert the
spindle speed with 57.66% contribution is the most
influencing factor in determining the multi-objective
characteristics or grey relational grade with equal
weights for Ra and MRR followed by feed 7.19%
contribution and depth of cut 34.66% contribution.
 For uncoated insert the depth of cut with 51.07%
contribution is the most influencing factor in
determining the multi-objective characteristics with
equal weights for Ra and MRR followed by spindle
speed 40.63% contribution and feed 5.87%
contribution.
 The best multi-objective characteristics obtained for
PVD coated TiAlN insert for turning of EN 8 alloy
steel with the higher spindle speed of 1800 rpm,
higher feed of 0.2 mm/rev. and higher depth of cut of
1.2 mm with the estimated multi-objective
characteristics 0.8107. The experimental value of
GRG for this combination of parameters is 0.8554.
 For coated insert, the percentage of error between
the predicted and experimental values of the multi-
objective characteristics during the confirmation
experiments is almost within 5.23%.
 The best multi-objective characteristics obtained for
uncoated insert for turning of EN 8 alloy steel with
the higher spindle speed of 1800 rpm, higher feed of
0.2 mm/rev. and higher depth of cut of 1.2 mm with
the estimated multi-objective characteristics of
0.7895. The experimental value of GRG for this
combination of parameters is 0.8224.
 For uncoated insert, the percentage of error between
the predicted and experimental values of the multi-
objective characteristics during the confirmation
experiments is almost within 4.01%
6. REFERENCES
[1.] J. S. Senthilkumaar, P. Selvarani, R. M. Arunachalam,
“Intelligent optimization and selection of machining
parameters in finish turning and facing of Inconel 718”,
International Journal of Advanced Manufacturing
Technology (2012) 58,885–894
[2.]Radhakrishnan Ramanujam, Nambi Muthukrishnan,
Ramasamy Raju, “Optimization of Cutting Parameters for
Turning Al-SiC(10p) MMC Using ANOVA and Grey
Relational Analysis”, International Journal of Precision
Engineering and Manufacturing, Vol. 12, pp. 651-656.
[3.] Chinnasamy Natarajan, S. Muthu, P. Karuppuswamy,
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characteristics of a non-ferrous material using ANN in CNC
turning”, International Journal of Advanced Manufacturing
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[4.] S. Rajesh, D. Devaraj, R. Sudhakara Pandian, S.
Rajakarunakaran, “Multi-response optimization of
machining parameters on red mud-based aluminum
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[5.] Tian-Syung Lan, Ming-Yung Wang, “Competitive
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Athmane Yallese, Salim Belhadi, Francois Girardin,
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[7.] P. Jayaraman, L. Mahesh kumar, “Multi-response
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Dewangan, Soumya Gangopadhyay, “Multi-Objective
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RachidM´Saoubi, “Experimental Study and Modelling of
Plastic Deformation of Cemented Carbide Tools in
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[11.] V. Bushlya, J. Zhou, J.E. Stahl, “Effect of Cutting
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PCBN Tools”, Procedia CIRP 3 ( 2012 ), 370 – 375.
[12.] Harsh Y Valera, Sanket N Bhavsar, “Experimental
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[13.] Suraj R. Jadhav, Aamir M. Shaikh, “Study on process
parameters for CNC turning using Taguchi Methods for
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American International Journal of Research in Science,
Technology, Engineering & Mathematics, (2015), vol. 1,
issue 12, pp. 69-73

Optimization of Process Parameters for CNC Turning using Taguchi Methods for EN8 Alloy Steel with Coated/Uncoated Tool Inserts

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Optimization of Process Parameters for CNC Turning using Taguchi Methods for EN8 Alloy Steel with Coated/Uncoated Tool Inserts