 Open Access
 Total Downloads : 110
 Authors : Janagarathinam. P, Tharoon. T , Senthilkumar. K. P
 Paper ID : IJERTV5IS090524
 Volume & Issue : Volume 05, Issue 09 (September 2016)
 DOI : http://dx.doi.org/10.17577/IJERTV5IS090524
 Published (First Online): 29092016
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
The Assessment of Delamination in the Drilling of EN8 Steel by using Taguchi Method
Janagarathinam . P1,
Assistant Professor, Department of Mechanical Engineering,
SNS College of Technology, Coimbatore,
Senthilkumar . K. P3
Assistant Professor,
Tharoon.T2
Student
Mechanical Engineering Department, SNS College of Technology, Coimbatore,
Department of Mechanical Engineering, Excel College of Engineering and Technology,
Pallakapalayam637303,
Abstract The application of EN8 steel is increased in engineering field particularly in textiles industries and automobile industries. Drilling of these material cannot be avoided to get the hole of required accuracy. The delamination occurs due to various parameters leading to poor machinability and surface finish. The aim of this paper is to study the relationships and parametric interaction between cutting parameters namely spindle speed, drill diameter and feed rate on the delamination factor at the exit of holes in drilling of EN8 steel. Delamination factor reduces the performance and aesthetical aspects of the final product [2, 11]. The experiments have been as per Taguchis L27 orthogonal array. Analysis of variance (ANOVA) was performed to verify the sufficiency of the mathematical model and it is used to find out the percentage contribution of each parameter, it shows that the delamination factor increase in feed rate and decrease in spindle speed.
Keywords: EN8 steel, Drilling, Delamination factor, ANOVA

INTRODUCTION
The application of EN8 steel is increased day by day especially textiles industries and automobile industries. EN8 is an unalloyed medium carbon steel. It is a medium strength steel, good tensile strength. Suitable for shafts, stressed pins, studs, keys etc. AISI 1040. Available as normalised or rolled. The chemical composition of EN8 is tabulated as given below
Table 1: Chemical composition of EN8 steel
Materials
Composition
Carbon
0.360.44%
Silicon
0.100.40%
Manganese
0.601.00%
Sulphur
0.050%
Phosphorus
0.050%
EN8 is a throughhardening medium carbon steel. Hardness of En8 never goes above approximately 3035 HRC. It is low carbon steel and it can be toughened. The degree of smoothness and accuracy of the hole while drilling of EN8 steel is affected by the delamination tendency of the material. The delamination affects the aesthetic aspects, reduction of strength, resulting in poor assembling.Taguchi design of experiments which is used to find out optimal cutting parameters for drilling operation. The main objective of this paper is to understand the influence of drilling parameters, to construct a mathematical model and to analyse the delamination factor with respect to various cutting parameters such as feed rate, spindle speed, drill diameter.

EXPERIMENTAL DETAILS

Material
In this paper deals EN8 steel material. The mechanical properties of EN8 steel material is given below:
Table 2: Mechanical Properties of EN8 Steel
Properties
Values
Maximum stress
700850 N/mm2
Yield stress
465 N/mm2
0.2% proof stress
450 N/mm2
Elongation
16%
Impact
28 J

Experimentation
In this paper high speed steel drill bits are used. Whose diameters are 6mm, 9mm, 12mm the drilling operations were carried in Heavy duty universal radial and pillory type drilling machine. Delamination has been measured using different techniques. In this paper we are using inexpensive technique. Delamination is measured during drilling process using a video profile projector. The equipments required for this technique are: video profile projector of 1/3 inch CCD video camera with high resolution telecentric zoom lens. The magnification of 30190 X is used. The specimen is placed directly on the top plate of the projector by means of imaging device, hole pictures are
captured and exported to 2D geometric measurement software and delamination values are calculated and tabulated [2].
Fig.1 delamination zone


DESIGN OF EXPERIMENTS
Design of experiments (DOE) is a systematic method to determine the relationship between factors affecting a process and the output of that process [6, 14]. In this paper the factors are considered such as feed rate, spindle speed, drill diameter. DOE, which give well designed set of experiments.

Experimental Parameters and Levels
The cutting parameters are feed rate, spindle speed, drill diameter these are influencing parameters which affects the delamination in drilling. The parameters and levels are set at three different levels, namely low, medium and high as shown in Table 3.

Taguchi L27 Orthogonal Array
In this paper we are using Taguchi L27 Orthogonal Array from which parameter values are derived and tabulated.
Table 4: parameters
Test No
Parameter values
Delamination Factor
Fd
f
mm/min
N
Rpm
d mm
1
100
500
6
1.02
2
100
500
9
1.04
3
100
500
12
1.05
4
100
1000
6
1.03
5
100
1000
9
1.05
6
100
1000
12
1.07
7
100
1500
6
1.05
8
100
1500
9
1.07
9
100
1500
12
1.09
10
300
500
6
1.13
11
300
500
9
1.15
12
300
500
12
1.16
13
300
1000
6
1.14
14
300
1000
9
1.15
15
300
1000
12
1.17
16
300
1500
6
1.18
17
300
1500
9
1.17
18
300
1500
12
1.19
19
500
500
6
1.24
20
500
500
9/p>
1.26
21
500
500
12
1.28
22
500
1000
6
1.27
23
500
1000
9
1.32
24
500
1000
12
1.29
25
500
1500
6
1.26
26
500
1500
9
1.27
27
500
1500
12
1.29
Test No
Parameter values
Delamination Factor
Fd
f
mm/min
N
Rpm
d mm
1
100
500
6
1.02
2
100
500
9
1.04
3
100
500
12
1.05
4
100
1000
6
1.03
5
100
1000
9
1.05
6
100
1000
12
1.07
7
100
1500
6
1.05
8
100
1500
9
1.07
9
100
1500
12
1.09
10
300
500
6
1.13
11
300
500
9
1.15
12
300
500
12
1.16
13
300
1000
6
1.14
14
300
1000
9
1.15
15
300
1000
12
1.17
16
300
1500
6
1.18
17
300
1500
9
1.17
18
300
1500
12
1.19
19
500
500
6
1.24
20
500
500
9
1.26
21
500
500
12
1.28
22
500
1000
6
1.27
23
500
1000
9
1.32
24
500
1000
12
1.29
25
500
1500
6
1.26
26
500
1500
9
1.27
27
500
1500
12
1.29
Thus 27 experiments were conducted from which the delamination factor are measured and tabulated as above.
Table 3: Parameters and levels
S.No
Parameters
Symbol
Units
Levels in Taguchi Design
Level I (Low)
Level II (Medium)
Level III (High)
1
Feed
F
mm/min
100
300
500
2
Spindle Speed
N
Rpm
500
1000
1500
3
Drill diameter
D
Mm
6
9
12
S.No
Parameters
Symbol
Units
Levels in Taguchi Design
Level I (Low)
Level II (Medium)
Level III (High)
1
Feed
F
mm/min
100
300
500
2
Spindle Speed
N
Rpm
500
1000
1500
3
Drill diameter
D
Mm
6
9
12
.


RESULTS AND DISCUSSION

Determination of the Regression model and Evaluation of Statistical
Mean of Means
Mean of Means
The Regression equation, ANOVA and Graph is generated by using Minitab software. The regression equation is give the relationship among feedrate, spindle speed tool diameter and delamination factor. The equation is given by,
Delamination Factor (Fd) = 0.923 + 0.000558 Feed Rate
+ 0.000027 Spindle Speed+0.005 Tool Diameter
Regression Analysis
The goodness of fit was clarified by the determination coefficient (R2).In this study, the value of determination coefficient is 0.984 which is indicated that 2% of the total variations were not explained by the regression model. The adjusted determination coefficient is 0.982. So we noticed that the adjusted determination coefficient is very closer to the determination coefficient which means a good correlation between the responses and the experimental results.

Taguchi Analysis
Main Effects Plot for Means
Data Means
Feed Rate Spindle Speed
Main Effects Plot for Means
Data Means
Feed Rate Spindle Speed
1.25
1.20
1.15
1.10
1.05
100
300
Tool Diameter
500
500
1000
1500
1.25
1.20
1.15
1.10
1.05
100
300
Tool Diameter
500
500
1000
1500
6
9
12
6
9
12
1.25
1.20
1.15
1.10
1.05
1.25
1.20
1.15
1.10
1.05
Graph 1: Mean Plot Graph
Main Effects Plot for SN ratios
Data Means
This method uses a special set of arrays called orthogonal arrays. These standard arrays stipulates the way of conducting the minimal number of experiments which could give the full information of all the factors that affect the performance parameter.
The crux of the orthogonal arrays method lies in choosing the level combinations of the input design variables for each experiment. The experiments were conducted and the delamination values were measured from which the following graphs were drawn by using Minitab software.
0.5
1.0
Mean of SN ratios
Mean of SN ratios
1.5
2.0
0.5
1.0
1.5
2.0
100
6
Feed Rate
300
Tool Diameter
9
500
12
500
Spindle Speed
1000
1500
Signaltonoise: Smaller is better
Graph 2: Signal to noise ratio Graph
Taguchi analysis is done as above we got signal to noise ratio graph and mean plot graph as shown in the figure. From which a major influencing factor is obtained such as feed rate. The second influencing factor is Tool diameter and the third influencing factor is Spindle Speed whose contribution is very less compared to other influencing factor

Normal Probability plot Graph
The normal probability plot graph is obtained by using the regression equation and the experimental values. It is a graphical representation for assessing whether data set is normally distributed or not. The graph should give approximately in a line. So the errors are distributed normally.

ANOVA
Analysis of variance (ANOVA) is a collection of statistical models used to analyse the differences among group means and their associated procedures. ANOVA was performed by the Minitab Software. Which give the effective values.
Regression Analysis
Table 5
4.5. Confirmation Test
The L27 array were conducted which means 27 experiments were conducted from which the percentage of error is calculated and tabulated (Table 6) at different conditions such as feed rate, spindle speed, tool diameter.
Predictor
Coefficient
SE Coefficient
T
P
Constant
0.92343
0.01212
76.21
0.00
Feed rate
0.00055833
0.00001519
36.77
0.00
Spindle Speed
0.00002667
0.00000607
4.39
0.00
Tool Diameter
0.005000
0.001012
4.94
0.00
S=0.0128850
R2=0.984
R2 (adj)=0.982

Taguchi Analysis: Response Table for Signal to Noise Ratios
Smaller is better
Table 6
Level
Feed Rate
Spindle Speed
Tool Diameter
1
0.4405
1.1690
1.1620
2
1.2881
1.2981
1.2932
3
2.1127
1.3742
1.3880
Delta
1.6722
0.2052
0.2278
Rank
1
3
2
Response Table for Means
Table 7
Level
Feed Rate
Spindle Speed
Tool Diameter
1
1.052
1.148
1.147
2
1.160
1.166
1.164
3
1.276
1.174
1.177
Delta
0.223
0.027
0.030
Rank
1
3
2

Normal Probability plot Graph
Normal Probability Plot
(response is Delamination Factor(Fd))
99
95
90
80
Percent
Percent
70
60
50
40
30
20
10
5
1
3 2 1 0
1 2 3 4
Standardized Residual

ANOVA TABLE
Graph 3 Normal probability plot
Table 8
Sources
DOF
SS
MS
F
P
% Contribution
Feed Rate
2
0.224541
0.112705
352.48
0.000
94.47
Spindle Speed
2
0.003319
0.0016595
5.21
0.016
1.43
Tool Diameter
2
0.004096
0.002048
0.16
0.852
1.72
Error
20
0.005733
0.0028665
2.48
Total
26
0.237689
100

Confirmation Test
Table 9
Trial No
Feed Rate
Spindle Speed
Tool Diameter
Experimental Delamination
Predicated Delamination
% Error
1.
150
700
6
1.04
1.05
0.96
2.
350
1250
9
1.21
1.19
1.65
3.
450
1800
12
1.27
1.28
0.78


CONCLUSION
In this paper, Taguchi Orthogonal is used to obtain the delamination factor in drilling process of EN8 steel. The following conclusions are done by this experiment

In Regression analysis, the adjusted determination coefficient is very closer to the determination coefficient so evaluation of delamination factor is done by effectively and efficiently.

Delamination factor increases with increase in feed and decrease in speed.

Feed was found to be the first influencing factor for the delamination of EN8 steel followed by drill diameter.

The normal probability plot graph is obtained in the form of straight line so the errors are distributed normally.


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