International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 1112–1119, Article ID: IJMET_10_01_114
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=1
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
©IAEME Publication
Scopus Indexed
OPTIMIZING GRINDING PARAMETERS FOR
SURFACE ROUGHNESS WHEN GRINDING
TABLET BY CBN GRINDING WHEEL ON CNC
MILLING MACHINE
Le Hong Ky
Vinh Long University of Technology Education, Vinh Long, Vietnam
Tran Thi Hong
Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam
Hoang Tien Dung
Ha Noi University of Industry, Ha Noi, Vietnam
Nguyen Van Tung, Nguyen Thi Thanh Nga, Luu Anh Tung, Vu Ngoc Pi
Thai Nguyen University of Technology, Thai Nguyen, Vietnam
*
Corresponding Author Email: vungocpi@tnut.edu.vn
ABSTRACT
Surface quality of a workpiece is one of the most important criteria for the
evaluation of a grinding process. Surface finish depends on many factors such as
grinding and dressing parameters. This paper presents an optimization of grinding
parameters when grinding tablet by CBN grinding wheel on CNC milling machine in
order to minimize surface roughness. The experiment was conducted with different
values of grinding parameters at three levels. Using the Taguchi method, the effect of
the grinding parameters i.e., depth of cut, grinding wheel speed, and feed rate on
surface roughness was investigated. In addition, the optimal grinding parameters
were found at their optimal levels. The predicted surface roughness was therefore
determined.
Key words: Optimal grinding parameters, surface roughness, CBN grinding wheel,
Taguchi method.
Cite this Article: Le Hong Ky, Tran Thi Hong, Hoang Tien Dung, Nguyen Van Tung,
Nguyen Thi Thanh Nga, Luu Anh Tung, Vu Ngoc Pi, Optimizing Grinding Parameters
for Surface Roughness when Grinding Tablet by CBN Grinding Wheel on CNC
Milling Machine, International Journal of Mechanical Engineering and Technology
(IJMET) 10(1), 2019, pp. 1112–1119.
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Le Hong Ky, Tran Thi Hong, Hoang Tien Dung, Nguyen Van Tung, Nguyen Thi Thanh Nga,
Luu Anh Tung, Vu Ngoc Pi
1. INTRODUCTION
In general, improving the dimensional accuracy and surface quality of a workpiece in a
grinding process, many grinding machining parameters could be considered. Analysis of
grinding parameters in cylindrical grinding was investigated by designing experiments [1-3].
The influence of dressing parameters in cylindrical grinding was proposed in [4-5]. These
researches presented the effect of several important dressing paremters i.e., dressing deep of
cut, cross feed rate, drag angle of dresser and number of passes on surface roughness. Lin et
al. [6] showed the influence of grinding parameters on surface temperature and burn behavior
of the grinding rail.
For regarding the optimization in grinding process, Agarwal [7] proposed an optimization
of various machining parameters such as depth, table feed, and size and density of grit on the
metal removal rate in order to obtain high surface integrity in grinding silicon carbide
ceramics. An enumeration method was used to optimize grinding operations based on
minimizing grinding time and maximizing the volume of material removed [8]. The optimal
grinding operations are material properties, grinding parameters, infeed, workpiece speed,
grinding wheel speed, and dress conditions. An optimization of grinding parameters in
cylindrical grinding process was investigated in order to minimize surface roughness [9,10].
In this work, the Taguchi technique was used to obtain the optimal grinding parameters. Le et
al. [11] was also used Taguchi method for optimizing the dressing parameters such as
dressing feed rate, coarse dressing depth, coarse dressing times, fine dressing depth, fine
dressing times, and dressing number without depth of cut in order to obtain maximum
material removal rate.
This study proposes an optimization of grinding parameters for surface roughness when
grinding tablet by CBN grinding wheel on CNC milling machine. The important grinding
parameters seclected in this work are the depth of cut, grinding wheel speed, and feed rate.
The Taguchi technique has been appied in order to determine the optimal grinding parameters
leading to minimize surface roughness. Furthermore, the predicted surface roughness was also
investigated.
2. EXPRERIMENTAL METHODOLOGY
A set of experiments was conducted on the CNC milling machine for grinding by using CBN
grinding wheel. The experiment equipment is shown in Table 1.
Table 1 Experimental equipment
Machine and Equipment
CNC milling machine
Grinding wheel
Workpiece material
Workpiece dimensions
Roughness measurement device
Specification
Mitsubishi, Model M-V50C
CBN 325-N75B53-3.0 (Japan)
9CrSi
13x13x30 mm3
Mitutoyo 178-923-2A, SJ-201
The experiments have been conducted on the basis of the Taguchi method in order to
design and analyze data of the experiments. For this, the effect of the grinding parameters on
the surface roughness when grinding tablet using the CBN grinding wheel on CNC Milling
Machine was investigated. The grinding parameters such as the depth of cut, grinding wheel
speed and feed rate were selected in the experiments. The ginding parameters and their value
range are shown in Table 2.
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Optimizing Grinding Parameters for Surface Roughness when Grinding Tablet by CBN Grinding Wheel on
CNC Milling Machine
Table 2. Ginding parameters and their value range
Factor
Depth of cut
Grinding wheel speed
Feed rate
Symbol
Unit
mm
r.p.m.
mm/min
Low
0.02
4000
2500
High
0.03
5000
3500
Table 3. Experiment work
Test run No.
(mm)
0.02
0.02
0.02
0.025
0.025
0.025
0.03
0.03
0.03
1
2
3
4
5
6
7
8
9
(r.p.m)
4000
4500
5000
4000
4500
5000
4000
4500
5000
(r.p.m)
2500
3000
3500
3000
3500
2500
3500
2500
3000
Fig.1. Experimental setup
a) Dressing setup
b) Grinding setup c) Schema of grinding
Minitab 17 was used to design the experiments with the three grinding parameters. By
using Taguchi method, L9 with nine test runs was used for the experiment work as shown in
Table 3. For increasing the accuracy of the experiment results, the three grinding parameters
and three trials were performed during the experimentation in each test run as shown in Table
4. The total of test runs is 27 for the experimentation.
The procedure of the experiment was conducted into three steps as follows:
- Step 1: The CBN grinding wheel is dressed by dresser equipment (Figure 1.a) according to
the dressing parameters are
mm;
r.p.m;
mm/min.
- Step 2: The workpieces are ground (Figure 2b) with schema in Figure 2c and the grinding
parameters in Table 2 with the three levels and the three trials.
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Le Hong Ky, Tran Thi Hong, Hoang Tien Dung, Nguyen Van Tung, Nguyen Thi Thanh Nga,
Luu Anh Tung, Vu Ngoc Pi
- Step 3: The surface roughness of the workpiece was measured by using the roughness
measurement device.
Table 4 Experiment results
Test run No.
Trial 1
0.413
0.589
0.494
0.622
0.693
0.793
0.887
0.650
0.886
1
2
3
4
5
6
7
8
9
Trial 2
0.407
0.664
0.508
0.608
0.712
0.778
0.901
0.634
0.880
Ra (m)
Trial 3
0.427
0.574
0.557
0.568
0.721
0.764
0.819
0.643
0.900
Mean
0.416
0.609
0.520
0.599
0.709
0.778
0.869
0.642
0.889
S/N
7.62
4.29
5.67
4.44
2.99
2.18
1.21
3.84
1.02
3. RESULT AND DISCUSSION
Surface roughness values are obtained from the Mitutoyo surface roughness tester for each
experiment. The values of surface roughness in three trial are shown in Table 3. The Taguchi
method was used for analyzing the values of surface roughness in order to depict the effect of
the grinding parameters on surface roughness and to determine the optimal grinding
parameters.
3.1. Effect of the grinding parameters on surface roughness
From the analysis of variance - ANOVA, Table 5 presents the effect of the grinding
parameters on the surface roughness at three levels. Table 6 and Fig.1 show the effect of the
grinding parameters on the surface roughness. It is clearly seen that the depth of cut has the
largest effect on the surface roughness. The effect of the grinding wheel speed and feed rate
decreases respectively.
Table 5. Effect of grinding parameters on surface roughness at different levels
Level
1
2
3
Delta
Rank
0.5148
0.6954
0.8000
0.2852
1
0.6280
0.6533
0.7289
0.1009
2
0.6121
0.6990
0.6991
0.0870
3
Fig.1 shows that the surface roughness tremendously increases when the depth of cut
increases. The surface roughness obtains the minimum value at 0.02m of the depth of cut.
The surface roughness also increases with increase of the grinding wheel speed and the feed
rate.
Table 6. Results of ANOVA analysis for the surface roughness
Source
Residual error
Total
DF
2
2
2
2
8
Seq SS
0.12492
0.01653
0.01512
0.04084
0.19741
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Adj SS
0.12492
0.01653
0.01512
0.04084
-
Adj MS
0.062462
0.008264
0.007559
0.020421
-
F
3.06
0.4
0.37
-
P
0.246
0.712
0.730
-
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Optimizing Grinding Parameters for Surface Roughness when Grinding Tablet by CBN Grinding Wheel on
CNC Milling Machine
Figure 1 Effect of the grinding parameters on surface roughness Ra
3.2. Determination of optimal grinding parameters
The Taguchi method uses the term ‘signal-to-noise’ (S/N) to measure the quality
characteristic deviation from the desired value. Thus, based on the maximum S/N ratio, the
optimum factors can be determined. Table 7 shows that the effect of the grinding parameters
such as the depth of cut, grinding wheel speed, and feed rate on the S/N ratio decreases
respectively. It is observed from Table 8 and Fig. 2 that the optimal grinding parameters are
obtained in order to achieve the minimum surface roughness. The optimal values of the
grinding parameters are
,
, and
.
Table 7 Effect of factors on the S/N ratio at their levels
Level
1
2
3
Delta
Rank
5.862
3.202
2.027
3.835
1
4.425
3.708
2.958
1.467
2
4.548
3.252
3.292
1.296
3
Table 8. Results of ANOVA analysis for S/N
Source
Residual error
Total
DF
2
2
2
2
8
Seq SS
23.165
3.229
3.259
6.725
36.378
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Adj SS
23.165
3.229
3.259
6.725
-
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Adj MS
11.582
1.615
1.629
3.362
-
F
3.44
0.48
0.48
-
P
0.225
0.676
0.674
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Le Hong Ky, Tran Thi Hong, Hoang Tien Dung, Nguyen Van Tung, Nguyen Thi Thanh Nga,
Luu Anh Tung, Vu Ngoc Pi
Figure 2 Effect of the grinding parameters on S/N ratio
The mean value of optimal surface roughness is determined from the optimum parameters
at their optimal levels. As shown in Table 7, level 1 is the optimal level of the three
parameters. Thus, the formula for computing the mean value of optimal surface roughness is
̅̅̅̅
̅̅̅
̅̅̅
̅̅̅
̅̅̅̅
(1)
Where
̅̅̅ is the mean value of surface roughness at the depth of cut
and ̅̅̅
̅̅̅ is the mean value of surface roughness at the grinding wheel speed
and ̅̅̅
̅̅̅ is the mean value of surface roughness at the feed rate
and ̅̅̅
̅̅̅̅ is the mean value of surface roughness for all test runs and it can be calculated as
̅̅̅̅
∑
∑
∑
(2)
Substituting all of the parameters ̅̅̅ ̅̅̅ ̅̅̅ and ̅̅̅̅̅̅ into Eq. (1), the mean value of
the surface roughness is calculated as
.
To evaluate the appropriateness of the optimum parameters, an experiment was conducted
with two replications. The data used in the experiment were: aed=0.02 mm, RPM= 4000 rpm,
Fe= 2500 mm/min. Table 9 shows the values of the surface roughness which was predicted by
using the mathematical model and the experiment results. The difference between both values
is appropriately 6.6 % of the range. Therefore, this calculation method can be used to
accurately predict the surface roughness of the ground parts.
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Optimizing Grinding Parameters for Surface Roughness when Grinding Tablet by CBN Grinding Wheel on
CNC Milling Machine
Table 9. Comparison results between calculation value and experimental value
Output factors
The surface roughness of part Ra (µm)
Signal-to-noise ratio (S/N)
Optimum parameters
Prediction value
Experimental value
aed2, RPM1, Fe1
aed2, RPM1, Fe1
0.4149
0.398
7.64
8.0
Error (%)
4.07
4. CONCLUSIONS
In this paper, the proposed designed experiment using Taguchi method with L9 orthogodinal
array was carried out to evaluate the effect of the grinding parameters and to find the optimal
parameters for surface roughness. The conclusion can be drawn as follows

It was found that the depth of cut is the most influencing factor on surface roughness
compared with the grinding wheel speed and feed rate.

The surface roughness is proportional to all of the grinding parameters.

The optimal values of the grinding parameters obtained for surface roughness using Taguchi
method of experiment methodology have been found as
.
ACKNOWLEDGMENTS
The work described in this paper was supported by Thai Nguyen University of Technology
for a scientific project.
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