Surface And Subsurface Analysis In Grinding Process.
1
2
3
ABSTRACT
The main aim of this study is to investigate the surface and subsurface quality of a
grinding process. Surface roughness and subsurface morphology is the most critical
quality measures in mechanical products. As competition among industries grows
rapidly, customers have highly demand on quality surface roughness and subsurface. In
metal manufacturing industries, grinding is one of the most popular methods of
machining hardened materials. The use of coolant and machine vibration is identified as
factors influencing the surface roughness besides the machining parameters and type of
material. The parameters choose in this study are depth of cut and feed rate and the
workpiece material is mild steel AISI 1020. The full factorial Design of Experiment
(DOE) method is used to study the effect of machined parameter on surface roughness.
The result of surface roughness was analyzed using MINITAB software. All of the
specimens were machined using surface grinding machine. Surface roughness was
analyzed using portable surface roughness. The surface morphology is analyzed by
using image analyzer and Scanning Electron Microscope (SEM). From the results, it
shows that the highest Ra value obtained is 0.58µm at the feed rate of 50 mm/min and
depth of cut 2.0µm whiles the lowest Ra value obtained is 0.20µm at feed rate of 90
mm/min and depth of cut 10.0µm. Surface roughness was found to be influenced by
feed rate rather than depth of cut. Dry grinding shows high surface roughness value
compare to using coolant.
4
ABSTRAK
Tujuan utama kajian ini adalah untuk mengkaji kekasaran permukaan dan morfologi
permukaan di dalam process pengasahan. Kekasaran permukaan dan permukaan bawah
adalah ukuran kualiti yang kritikal di dalam kebanyakan produk mekanikal. Persaingan
dalam industri yang semakin berkembang maju menyebabkan para pengguna
mementingkan kualiti kekasaran permukaan dan permukaan bawah. Dalam industri
pembuatan logam, pengasah permukaan adalah salah sebuah kaedah terbaik yang
digunakan untuk mengasah bahan kerja yang keras. Penggunaan cecair penyejuk dan
getaran mesin adalah faktor yang mempengaruhi kekasaran permukan disamping
parameter pemesinan dan jenis bahan kerja. Parameter yang dipilih dalam projek ini
adalah kelajuan pemakanan (feed rate) dan kedalaman pemotongan pengasahan (depth
of cut) mesin permukaan. Selain itu, bahan yang dipilih adalah keluli sederhana (mild
steel) AISI 1020. Projek ini mengaplikasikan kaedah rekabentuk eksperimen untuk
mengkaji kesan parameter pada kekasaran permukaan. Hasil kekasaran permukaan akan
dianalisa menggunakan perisian MINITAB. Semua spesimen dimesin menggunakan
mesin pengasah permukaan. Kekasaran permukaan dianalisis menggunakan mesin
kekasaran permukaan dan morfologi permukaan dianalisis menggunakan pengimbas
mikroskop elektron (SEM). Keputusan analisis menunjukkan kekasaran permukaan
paling tinggi adalah 0.58µm pada nilai pemakanan (feed rate) 50mm/min dan kedalaman
pemotongan (depth of cut) 10µm.
Kekasaran permukaan menunjukkan ianya
dipengaruhi oleh nilai pemakanan berbanding kedalaman pemotongan. Proses
pengasahan tanpa cecair penyejuk menunjukkan nilai kekasaran permukaan yang tinggi
berbanding menggunakan cecair penyejuk.
5
DEDICATION
Special thanks for my supervisor, Dr Ahmad Kamely Bin Mohamad
For my beloved parent, my brother and my sister.
Especially for my special one who believing in me and supporting everything I do.
6
ACKNOWLEDGEMENTS
Alhamdulillah, finally I have finished my Final Year Project. First and foremost, I
would like to dedicate my deepest gratitude to University Teknikal Malaysia Melaka,
especially for Faculty of Manufacturing for the provision of funding to carry out this
research and my bachelor degree study. A special thanks to my supervisor, Dr Ahmad
Kamely for the supervision along the time I was doing this project. I greatly appreciate
his consistent encouragement, advice and invaluable guidance throughout the course of
this project. I also like to express my thanks to all technician staff at FKP Laboratory
that helping me to get information through their explanation. Finally, I would like to
thank for my family members for their love, sacrifice, motivation and support given
during the course of this project. Last but not least, thanks for those who have
contributed directly or indirectly toward the success of this project.
7
TABLE OF CONTENT
Declaration
i
Approval
ii
Abstract
iii
Abstrak
iv
Dedication
v
Acknowledgements
vi
Table of contents
vii
List of tables
x
List of figures
xi
List abbreviations
xv
1. INTRODUCTION
1
1.1 Background
1
1.2 Problem Statements
4
1.3 Objectives
4
1.4 Scope of study
5
2. LITERATURE REVIEW
6
2.1 Introduction to high speed grinding
6
2.1.1 Advantages of high speed grinding
7
2.1.2 Disadvantages or problems in high speed grinding
8
2.2 Surface texture and surface roughness
9
2.3 Surface structure and properties
10
2.4 Surface roughness profile parameters
11
2.4.1 Roughness average, Ra
12
2.4.2 Arithmetic mean, Rz
12
2.4.3 Root mean square average, Rq
13
2.5 White layers
13
8
2.5.1 Factors occurrence of white layers
15
2.6 Surface grinders and accessories
16
2.6.1 The grinding wheel
16
2.6.1.1 Type of grinding wheel
17
2.6.2 The bonded abrasive
19
2.6.3 Comparison conventional and superabrasive wheel design
20
2.6.4 The grinding process
21
2.6.5 Surface finish
22
2.7 Vibration
22
2.8 Design of Experiments (DOE)
24
3. METHODOLOGY
26
3.1 Introduction
26
3.1.1 Project planning
27
3.2 Design of Experiment (DOE)
31
3.2.1 Stage 1: Define experiment objective
31
3.2.2 Stage 2: Control factors and their level identified
31
3.2.2.1 Surface grinding parameters
32
3.2.2.2 Wheel speed
32
3.2.2.3 Material
33
3.2.3 Stage 3: Identified suitable response variables
34
3.2.4 Stage 4: Selected appropriate Orthogonal Array (OA)
35
3.2.5 Stage 5: Prepare the experiment
35
3.2.5.1 Machine preparation
35
3.2.5.2 Machine setup
36
3.2.5.3 Grinding wheel balancing
36
3.2.5.4 Grinding wheel dressing and truing
38
3.2.5.5 Constant temperature
39
3.2.5.6 Constant place
40
3.2.5.7 Workpiece preparation
41
3.2.5.8 Selection of workpiece material
42
9
3.2.5.9 Experiments procedure and equipment
42
3.2.5.10 Machine specifications
42
3.2.5.11 Tools and equipments
47
3.2.5.12 Selection of method for analysis
52
3.2.5.13 Data processing flow
58
4. RESULT AND DISCUSSION
61
4.1 Introduction
61
4.2 Analysis method
61
4.3 Surface roughness analysis
62
4.4 Surface and subsurface analysis
67
4.4.1 Using coolant
67
4.4.2 Without using coolant
68
4.5 Factors affecting the surface roughness
79
5. CONCLUSION AND RECOMMENDATION
82
5.1 Conclusion
82
5.2 Recommendation
83
REFERENCES
85
APPENDICES
A
Surface texture standard
B
ASTM standard
C
Surface roughness profile
10
LIST OF TABLES
2.1
Fundamental pattern of a 2-level, 3 factor full factorial
25
3.1
Gantt chart for the Project Sarjana Muda 1 (PSM1)
29
3.2
Gantt chart for the Project Sarjana Muda 2 (PSM2)
30
3.3
Factors and levels selected for the experiments
31
3.4
Typical range of speeds and feeds for abrasive pProcess
33
(Kalpakjian, 2001)
3.5
Chemical composition of the materials
34
3.6
AISI 1020 mechanical properties (geocities, 2008)
34
3.7
Experimental layout with response value
35
3.8
Surface grinding machine specification
43
3.9
Portable roughness measuring machine accessories function
51
3.10
General specification of Mitutoyo Surface Roughness Tester, SJ-301
51
4.1
Mild steel analysis data
62
4.2
Comparison the surface roughness between use coolant and
without coolant
73
4.3
Comparison of thickness Heat Affected Zone (HAZ) between
75
depth of cut
4.4
Comparison of thickness Heat Affected Zone (HAZ) between feed rate
76
4.5
Comparison of thickness Heat Affected Zone (HAZ) between surface
77
roughness (Ra) using coolant
4.6
Comparison of thickness Heat Affected Zone (HAZ) between surface
roughness (Ra) without coolant
11
78
LIST OF FIGURES
2.1
The surface texture
9
2.2
Schematic illustration of a cross-section of the surface structure
11
of metals. The thickness of the individual layers depends on both
processing conditions and processing environment (Kalpakjian,
2001)
2.3
Standard terminology and symbols to describe surface finish
11
(Kalpakjian, 2001)
2.4
The arithmetic mean value, Ra
12
2.5
Coordinates used surface roughness (Kalpakjian, 2001)
13
2.6
Schematic section through machine surface (Bosheh et al., 2005)
14
2.7
Straight wheel (Wikipedia, 2008)
17
2.8
Diamond wheel (Wikipedia, 2008)
18
2.9
Structure, wear and fracture pattern of grinding wheels
19
(Kalpakjian, 2001)
2.10
Conventional abrasive wheel (Marinescu, 2006)
20
2.11
High speed CBN wheel. (Marinescu, 2006)
20
2.12
Cutting action of abrasive machining (Kalpakjian, 2001)
21
2.13
Three stages of chip generation and grinding force components
23
3.1
Flow chart of project
28
3.2
PSGC-60220 AHR grinding surface machine
36
3.3
Diamond dresser
37
3.4
A grinding wheel – balancing stand (Krar, 2004)
37
3.5
Adjusting counterbalances to balance a grinding wheel
38
(Marinescu, 2006)
3.6
A diamond dresser used to true and dress a grinding wheel
38
(Krar, 2004)
3.7
Truing makes the wheel round and true with its axis (Marinescu, 2006)
12
39
3.8
Grinding operation use the flood system to keep the workpiece cool.
40
3.9
Horizontal table
40
3.10
Workpiece on the horizontal table
41
3.11
Sample of workpiece (mild steel)
41
3.12
Work piece’s dimension
42
3.13
Surface grinding machine
43
3.14
Controller
44
3.15
The grinding wheel
44
3.16
Magnetic table
45
3.17
Pretech Cool SYN 3000 Green
45
3.18
Horizontal band saw
46
3.19
Pedestal grinding machine
46
3.20
Taking a reading of vibration before machining
47
3.21
Mallet
48
3.22
File
48
3.23
Oil
49
3.24
Degreaser and cleaner
49
3.25
Portable roughness measuring machine
50
3.26
Portable roughness measuring machine accessories
50
3.27
Stylus
50
3.28
Optical microscope
52
3.29
Automatic mounting press machine
53
3.30
Specimen were mounting
53
3.31
Sand paper grinding machine
54
3.32
Grinding and polishing machine
54
3.33
Alumina powder
55
3.34
Distil water
55
3.35
Nitric acid
56
3.36
Ethanol
56
3.37
Stirring hotplate machine
57
3.38
Optical microscope
57
13
3.39
Measuring roughness of the workpiece
58
3.40
Printing the result
58
3.41
Data processing flow
59
3.42
Calibrate the precision roughness specimen
60
4.1 Minitab report for mild steel analysis
63
4.2 Data analysis in MINITAB 14
64
4.3 Main effects plot (fitted means) for Ra (µm)
64
4.4 Interaction plot (fitted means) for Ra (µm)
65
4.5 Estimate response surface plot of Ra vs. depth of cut, feed rate
66
4.6 Normal probability plots of residual
66
4.7 Surface roughness texture (Ra) when grinding at different parameter .500X.
(Use coolant)
69
4.8 Photomicrograph of mild steel having a microstructure consisting
70
of pearlite and proeutectoid when grinding at different parameter.
1000X (use coolant)
4.9 Surface roughness Texture (Ra) when grinding at different parameter .
500X. (Without Coolant)
71
4.10 Photomicrograph of mild steel having a microstructure consisting
72
of pearlite and proeutectoid when grinding at different parameter.1000X.
(Without Coolant)
4.11 Graph of comparison surface roughness between use coolant
73
and without coolant
4.12 Photomicrograph of Heat Affected Zone (HAZ) layer of mild steel above
74
(no coolant) and below (use coolant) .200X
4.13 Graph of comparison thickness of HAZ and depth of cut
75
4.14 Graph of comparison thickness of HAZ and feed rate
76
4.15 Graph of comparison thickness of HAZ between surface roughness
77
using coolant
4.16 Graph of comparison thickness of HAZ between surface roughness
78
without coolant
4.17 Influence of arrangement and number of cleaning nozzle on surface quality 79
14
during surface grinding (Marinescu, 2001)
4.18 Influence of different type of cooling lubricants on surface quality during
80
surface grinding (Marinescu, 2001)
4.19 Types of grinding wheel wear (Marinescu, 2001).
15
81
LIST ABBREVIATIONS
DOE
-
Design of Experiment
UTeM
-
Universiti Teknikal Malaysia Melaka
PSM
-
Projek Sarjana Muda
HSG
-
High Speed Grinding
ANSI
-
American National Standard Institute
ASTM
-
American Society for Testing and Materials
ISO
-
International Standard Organization
Ra
-
Roughness average
AA
-
Arithmetic average
CLA
-
Centre line average
Rz
-
Arithmetic mean
RMS
-
Root mean square
HAZ
Heat Affected Zone
16
CHAPTER 1
INTRODUCTION
1.1 Background
Grinding is one type of machining processes which utilizes hard abrasive particles as the
cutting medium. Grinding is traditionally regarded as a final machining process in the
production of components requiring smooth surfaces and fine tolerances. Nowadays,
grinding is a major manufacturing process which accounts for about 20-25% of the total
expenditures on machining operations in manufacturing countries (Malkin, 1998). When
compare grinding machine and lathe machine, there are many major different especially
type of operations. As we know, grinding machine is used to perform a grinding process.
The selection of the grinding process is depends on part shape and size, ease of fixturing
and the production rate required. Grinding operations are carried out with a variety of
wheel and workpiece configurations. The basic types of grinding operations are surface
grinding, cylindrical grinding, internal grinding and centerless grinding (Kalpakjian,
2001). Surface grinders are the largest percentage of user in manufacturing industries
compare with other type of process in grinding. For the lathe machine, it’s still known as
the oldest machine tools, simple and versatile machine. The operation process on the
lathe machine required a skilled machinist because all controls are manipulated by hand.
The type process can be done by lathe machines are turning, boring, drilling, milling,
planning, shaping, broaching and sawing.
The important aspect in selection of grinding machine is grinding wheel. The type of
grinding wheel used for a certain application can greatly influence the quality of
17
surfaces produced, as well as the economics of the operation. The selection process on
wheels not only the shape of wheel and part to be produce, but it also consider on
characteristics of the workpiece material as well. The grindability of materials consider
such as the quality of the surface produced, surface finish, surface integrity, wheel wear,
cycle time and overall economics. In manufacturing industries today, the using of
ceramics as grinding wheel increase relative ease using diamond wheel. The ability of
this wheel material is possible to produce continuous chips and good surface integrity in
grinding (Malkin, 1998). The ceramic chips sizes are typically 1 µm-10 µm (40µin400µin). There are also has another various type of materials that recommends for
grinding wheels like Aluminum, Brass, Bronze, Cast iron, Carbides, Ceramics, Copper,
Nickel alloys, Nylon, Steels, Titanium and Tool steels. These recommendations
materials vary significantly, depending on material composition, grinding operation and
grinding fluids used.
As equipment in manufacturing machining, grinding machine also has advantage and
disadvantage. The grinding machines are available for various workpiece, geometries
and size. But, for the lathe machine the workpiece with cylindrical shape only available
to be machining on lathe machine. In production, grinding machine now was completed
with computer controlled. It has features such as automatic workpiece loading and
unloading, clamping, cycling, gaging, dressing and wheel shaping. Beside that, grinders
also equipped with probe and gages for determining the relative position of the wheel
and workpiece surface. For the limitations of grinding machines, grinding requires much
energy than turning process. So, thermal and other damage to the workpiece surface is
more likely to occurred and cutting fluid is necessary than machine tool more expensive.
It is evident that the competitive position of hard turning verse grinding must be
evaluated individually for each application and in terms of product surface finish and
integrity, quality and overall economics.
For grinding mechanisms, High Speed Grinding (HSG) is one of the most popular
processes in manufacturing industries. To reduce the cycle time, high speed grinding is
needed for a certain process. High speed grinding has been used in certain process that
18
need to remove material as quickly and efficiently as possible with little concern for
surface quality. In gathering a good surface finish, grinding machining used in the
production and is important part of the machine tool trade to improved machine
construction has permitted the production of parts to extremely fine tolerances with
improved surface finish and accuracy of the finish product (Krar, 2006). In the HSG, the
parameter can be observed like surface roughness, speed, depth of cut and feed rate.
According to Kalpakjian (2001), increase the wheel speed, depth of cut and wheel
diameter will increase temperature. But, temperature decreases with increasing
workpiece speed. So, temperature rise in grinding is an important consideration because
it can adversely affect the surface quality and cause residual stresses on the workpiece.
19
1.2 Problems Statements
The quality of a machined surface is becoming more and more important in order to
satisfy the increasing demands of sophisticated component performance, longevity, and
reliability. An understanding of surface integrity provides much advantage in avoiding
failures, enhance component integrity and reduce overall costs. Although considerable
research has been done on high speed grinding, there is hardly any research following on
the AISI D2 cold work tool steel. Many researchers have shown that grinding process
can induce white layer. The presence of white layer in HSG and it causes still be a great
concerns in the machining industries and academia because the effect of the white layer
on a components service life has not yet been clarified as understood at present.
1.3 Objectives
The objectives of this research are:
i.
To study the influence of heat on the surface morphology in grinding process.
ii.
To find the significant machining parameters (depth of cut and feed rate) that
influence machining characteristics through (DOE).
iii.
To analyze the data from the experiment using MINITAB software.
20
1.4 Scope of Study
This research will involve experimentation by machining parts using surface grinding
machine in UTeM machine shop. The grinding parameter that had been used was feed
rate and depth of cut and the material that had been choose for this analysis is Mild Steel
AISI 1020. The process of the experiment had been analyzed under the process of using
coolant and without using coolant. After the machining process, all those specimens will
be analyzed by using the portable roughness measuring machine. The specimens will
also be analyzing using optical microscope for analyzing the effect of Heat Affected
Zone (HAZ). Besides, the result of the specimen microstructure will be compare with
microstructure of other specimens which by using differences parameter. The result of
surface roughness had also been analyzed by using Design of Experiment (DOE)
method. Through this method, the data is analyzed using the full factorial design.
21
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction to High Speed Grinding
High speed grinding is one type of process in manufacturing industries to reduce the
production time. It is required in a certain process and material. HSG could be an
economic strategy for achieving high efficiency in machining process. Applications of
high speed grinding have expanded the field of grinding from traditional finishing
operation to now more widely employed high-performance machining. In this way, high
performance grinding corresponds to the dual attributes of high efficiency and high
precision, which are required for competitive grinding processes.
HSG is characterized by efforts to improve the economics of the process by increasing
material removal rates and simultaneous improvements of process stability, capability
and machining quality (Kopac et al., 2006). Besides that, in technological terms HSG
refer to high productivity grinding in order to reduce the machining time while
maintaining the same level of quality and high quality grinding in order to enhance
machining quality while maintaining a constant machining capacity. As a theoretical, an
increase in wheel speed results in a reduction in maximum chip thickness and hence
grinding force which should promote ductile flow by reducing the tendency for brittle
fracture (Huang, 2002). In his research, Huang (2002) used Silicon nitride with resin
bond diamond wheel as a material. High wheel speeds will introduce other factors such
as vibration and wheel wear. In addition, the wheel speed and other grinding parameters
will be effect on the surface quality. Beside that, the effect of vibration by the
unbalanced wheel at high speeds will affect the surface roughness quality.
26
Surface grinding was employed in a down grinding mode. The effect on grinding
performance is caused by various wheel speeds, wheel depths of cut and feed rates.
According to Huang et al. (2001), he claims the lowest speed is 40m/s and the highest
speed is 80m/s and above. Increasing the wheel speed substantially reduced the
maximum chip thickness during grinding, which resulted in a lower grinding force
(Huang, 2002). In addition, it was also seen that the depth of cut had an importance
influence on the grinding force. A larger depth of cut led to a higher grinding force.
According to Huang (2002), it was found that higher grinding speed caused less
subsurface damage because a smaller grinding force was associated with the grinding
process. So, the application of high wheel speeds was useful to compensate for the
subsurface damage caused by high speed grinding and also has many advantages to
manufacturing industries.
2.1.1 Advantages of High Speed Grinding
High speed machining, like the grinding of hard materials at higher speeds increasingly
applied in the manufacturing industries. This technology is possible to execute final
machining operations without consequent grinding or similar finishing operations. This
machining process can produce high productivity, good surface finish quality and higher
dimensional tolerances. In this way, an increased cutting speed is prerequisite for
increased productivity. The tool life of high performance grinding wheels also increased.
The grinding tools for HSG are subjected to special requirements in terms of their
operational speed and resistance to wear and fracture (Kopac et al., 2006). Besides that,
high speed grinding more efficiently and can save production time. It is also suitable
used for finishing process. High sped grinding also can improve product quality in
combination with increased throughput and reduced production time. HSG can maintain
the machine tool reliability and in-process sensing product quality. Also, the increase in
the cutting speed is expected to cause a reduction in cutting forces (Bosheh et al., 2005).
27
2
3
ABSTRACT
The main aim of this study is to investigate the surface and subsurface quality of a
grinding process. Surface roughness and subsurface morphology is the most critical
quality measures in mechanical products. As competition among industries grows
rapidly, customers have highly demand on quality surface roughness and subsurface. In
metal manufacturing industries, grinding is one of the most popular methods of
machining hardened materials. The use of coolant and machine vibration is identified as
factors influencing the surface roughness besides the machining parameters and type of
material. The parameters choose in this study are depth of cut and feed rate and the
workpiece material is mild steel AISI 1020. The full factorial Design of Experiment
(DOE) method is used to study the effect of machined parameter on surface roughness.
The result of surface roughness was analyzed using MINITAB software. All of the
specimens were machined using surface grinding machine. Surface roughness was
analyzed using portable surface roughness. The surface morphology is analyzed by
using image analyzer and Scanning Electron Microscope (SEM). From the results, it
shows that the highest Ra value obtained is 0.58µm at the feed rate of 50 mm/min and
depth of cut 2.0µm whiles the lowest Ra value obtained is 0.20µm at feed rate of 90
mm/min and depth of cut 10.0µm. Surface roughness was found to be influenced by
feed rate rather than depth of cut. Dry grinding shows high surface roughness value
compare to using coolant.
4
ABSTRAK
Tujuan utama kajian ini adalah untuk mengkaji kekasaran permukaan dan morfologi
permukaan di dalam process pengasahan. Kekasaran permukaan dan permukaan bawah
adalah ukuran kualiti yang kritikal di dalam kebanyakan produk mekanikal. Persaingan
dalam industri yang semakin berkembang maju menyebabkan para pengguna
mementingkan kualiti kekasaran permukaan dan permukaan bawah. Dalam industri
pembuatan logam, pengasah permukaan adalah salah sebuah kaedah terbaik yang
digunakan untuk mengasah bahan kerja yang keras. Penggunaan cecair penyejuk dan
getaran mesin adalah faktor yang mempengaruhi kekasaran permukan disamping
parameter pemesinan dan jenis bahan kerja. Parameter yang dipilih dalam projek ini
adalah kelajuan pemakanan (feed rate) dan kedalaman pemotongan pengasahan (depth
of cut) mesin permukaan. Selain itu, bahan yang dipilih adalah keluli sederhana (mild
steel) AISI 1020. Projek ini mengaplikasikan kaedah rekabentuk eksperimen untuk
mengkaji kesan parameter pada kekasaran permukaan. Hasil kekasaran permukaan akan
dianalisa menggunakan perisian MINITAB. Semua spesimen dimesin menggunakan
mesin pengasah permukaan. Kekasaran permukaan dianalisis menggunakan mesin
kekasaran permukaan dan morfologi permukaan dianalisis menggunakan pengimbas
mikroskop elektron (SEM). Keputusan analisis menunjukkan kekasaran permukaan
paling tinggi adalah 0.58µm pada nilai pemakanan (feed rate) 50mm/min dan kedalaman
pemotongan (depth of cut) 10µm.
Kekasaran permukaan menunjukkan ianya
dipengaruhi oleh nilai pemakanan berbanding kedalaman pemotongan. Proses
pengasahan tanpa cecair penyejuk menunjukkan nilai kekasaran permukaan yang tinggi
berbanding menggunakan cecair penyejuk.
5
DEDICATION
Special thanks for my supervisor, Dr Ahmad Kamely Bin Mohamad
For my beloved parent, my brother and my sister.
Especially for my special one who believing in me and supporting everything I do.
6
ACKNOWLEDGEMENTS
Alhamdulillah, finally I have finished my Final Year Project. First and foremost, I
would like to dedicate my deepest gratitude to University Teknikal Malaysia Melaka,
especially for Faculty of Manufacturing for the provision of funding to carry out this
research and my bachelor degree study. A special thanks to my supervisor, Dr Ahmad
Kamely for the supervision along the time I was doing this project. I greatly appreciate
his consistent encouragement, advice and invaluable guidance throughout the course of
this project. I also like to express my thanks to all technician staff at FKP Laboratory
that helping me to get information through their explanation. Finally, I would like to
thank for my family members for their love, sacrifice, motivation and support given
during the course of this project. Last but not least, thanks for those who have
contributed directly or indirectly toward the success of this project.
7
TABLE OF CONTENT
Declaration
i
Approval
ii
Abstract
iii
Abstrak
iv
Dedication
v
Acknowledgements
vi
Table of contents
vii
List of tables
x
List of figures
xi
List abbreviations
xv
1. INTRODUCTION
1
1.1 Background
1
1.2 Problem Statements
4
1.3 Objectives
4
1.4 Scope of study
5
2. LITERATURE REVIEW
6
2.1 Introduction to high speed grinding
6
2.1.1 Advantages of high speed grinding
7
2.1.2 Disadvantages or problems in high speed grinding
8
2.2 Surface texture and surface roughness
9
2.3 Surface structure and properties
10
2.4 Surface roughness profile parameters
11
2.4.1 Roughness average, Ra
12
2.4.2 Arithmetic mean, Rz
12
2.4.3 Root mean square average, Rq
13
2.5 White layers
13
8
2.5.1 Factors occurrence of white layers
15
2.6 Surface grinders and accessories
16
2.6.1 The grinding wheel
16
2.6.1.1 Type of grinding wheel
17
2.6.2 The bonded abrasive
19
2.6.3 Comparison conventional and superabrasive wheel design
20
2.6.4 The grinding process
21
2.6.5 Surface finish
22
2.7 Vibration
22
2.8 Design of Experiments (DOE)
24
3. METHODOLOGY
26
3.1 Introduction
26
3.1.1 Project planning
27
3.2 Design of Experiment (DOE)
31
3.2.1 Stage 1: Define experiment objective
31
3.2.2 Stage 2: Control factors and their level identified
31
3.2.2.1 Surface grinding parameters
32
3.2.2.2 Wheel speed
32
3.2.2.3 Material
33
3.2.3 Stage 3: Identified suitable response variables
34
3.2.4 Stage 4: Selected appropriate Orthogonal Array (OA)
35
3.2.5 Stage 5: Prepare the experiment
35
3.2.5.1 Machine preparation
35
3.2.5.2 Machine setup
36
3.2.5.3 Grinding wheel balancing
36
3.2.5.4 Grinding wheel dressing and truing
38
3.2.5.5 Constant temperature
39
3.2.5.6 Constant place
40
3.2.5.7 Workpiece preparation
41
3.2.5.8 Selection of workpiece material
42
9
3.2.5.9 Experiments procedure and equipment
42
3.2.5.10 Machine specifications
42
3.2.5.11 Tools and equipments
47
3.2.5.12 Selection of method for analysis
52
3.2.5.13 Data processing flow
58
4. RESULT AND DISCUSSION
61
4.1 Introduction
61
4.2 Analysis method
61
4.3 Surface roughness analysis
62
4.4 Surface and subsurface analysis
67
4.4.1 Using coolant
67
4.4.2 Without using coolant
68
4.5 Factors affecting the surface roughness
79
5. CONCLUSION AND RECOMMENDATION
82
5.1 Conclusion
82
5.2 Recommendation
83
REFERENCES
85
APPENDICES
A
Surface texture standard
B
ASTM standard
C
Surface roughness profile
10
LIST OF TABLES
2.1
Fundamental pattern of a 2-level, 3 factor full factorial
25
3.1
Gantt chart for the Project Sarjana Muda 1 (PSM1)
29
3.2
Gantt chart for the Project Sarjana Muda 2 (PSM2)
30
3.3
Factors and levels selected for the experiments
31
3.4
Typical range of speeds and feeds for abrasive pProcess
33
(Kalpakjian, 2001)
3.5
Chemical composition of the materials
34
3.6
AISI 1020 mechanical properties (geocities, 2008)
34
3.7
Experimental layout with response value
35
3.8
Surface grinding machine specification
43
3.9
Portable roughness measuring machine accessories function
51
3.10
General specification of Mitutoyo Surface Roughness Tester, SJ-301
51
4.1
Mild steel analysis data
62
4.2
Comparison the surface roughness between use coolant and
without coolant
73
4.3
Comparison of thickness Heat Affected Zone (HAZ) between
75
depth of cut
4.4
Comparison of thickness Heat Affected Zone (HAZ) between feed rate
76
4.5
Comparison of thickness Heat Affected Zone (HAZ) between surface
77
roughness (Ra) using coolant
4.6
Comparison of thickness Heat Affected Zone (HAZ) between surface
roughness (Ra) without coolant
11
78
LIST OF FIGURES
2.1
The surface texture
9
2.2
Schematic illustration of a cross-section of the surface structure
11
of metals. The thickness of the individual layers depends on both
processing conditions and processing environment (Kalpakjian,
2001)
2.3
Standard terminology and symbols to describe surface finish
11
(Kalpakjian, 2001)
2.4
The arithmetic mean value, Ra
12
2.5
Coordinates used surface roughness (Kalpakjian, 2001)
13
2.6
Schematic section through machine surface (Bosheh et al., 2005)
14
2.7
Straight wheel (Wikipedia, 2008)
17
2.8
Diamond wheel (Wikipedia, 2008)
18
2.9
Structure, wear and fracture pattern of grinding wheels
19
(Kalpakjian, 2001)
2.10
Conventional abrasive wheel (Marinescu, 2006)
20
2.11
High speed CBN wheel. (Marinescu, 2006)
20
2.12
Cutting action of abrasive machining (Kalpakjian, 2001)
21
2.13
Three stages of chip generation and grinding force components
23
3.1
Flow chart of project
28
3.2
PSGC-60220 AHR grinding surface machine
36
3.3
Diamond dresser
37
3.4
A grinding wheel – balancing stand (Krar, 2004)
37
3.5
Adjusting counterbalances to balance a grinding wheel
38
(Marinescu, 2006)
3.6
A diamond dresser used to true and dress a grinding wheel
38
(Krar, 2004)
3.7
Truing makes the wheel round and true with its axis (Marinescu, 2006)
12
39
3.8
Grinding operation use the flood system to keep the workpiece cool.
40
3.9
Horizontal table
40
3.10
Workpiece on the horizontal table
41
3.11
Sample of workpiece (mild steel)
41
3.12
Work piece’s dimension
42
3.13
Surface grinding machine
43
3.14
Controller
44
3.15
The grinding wheel
44
3.16
Magnetic table
45
3.17
Pretech Cool SYN 3000 Green
45
3.18
Horizontal band saw
46
3.19
Pedestal grinding machine
46
3.20
Taking a reading of vibration before machining
47
3.21
Mallet
48
3.22
File
48
3.23
Oil
49
3.24
Degreaser and cleaner
49
3.25
Portable roughness measuring machine
50
3.26
Portable roughness measuring machine accessories
50
3.27
Stylus
50
3.28
Optical microscope
52
3.29
Automatic mounting press machine
53
3.30
Specimen were mounting
53
3.31
Sand paper grinding machine
54
3.32
Grinding and polishing machine
54
3.33
Alumina powder
55
3.34
Distil water
55
3.35
Nitric acid
56
3.36
Ethanol
56
3.37
Stirring hotplate machine
57
3.38
Optical microscope
57
13
3.39
Measuring roughness of the workpiece
58
3.40
Printing the result
58
3.41
Data processing flow
59
3.42
Calibrate the precision roughness specimen
60
4.1 Minitab report for mild steel analysis
63
4.2 Data analysis in MINITAB 14
64
4.3 Main effects plot (fitted means) for Ra (µm)
64
4.4 Interaction plot (fitted means) for Ra (µm)
65
4.5 Estimate response surface plot of Ra vs. depth of cut, feed rate
66
4.6 Normal probability plots of residual
66
4.7 Surface roughness texture (Ra) when grinding at different parameter .500X.
(Use coolant)
69
4.8 Photomicrograph of mild steel having a microstructure consisting
70
of pearlite and proeutectoid when grinding at different parameter.
1000X (use coolant)
4.9 Surface roughness Texture (Ra) when grinding at different parameter .
500X. (Without Coolant)
71
4.10 Photomicrograph of mild steel having a microstructure consisting
72
of pearlite and proeutectoid when grinding at different parameter.1000X.
(Without Coolant)
4.11 Graph of comparison surface roughness between use coolant
73
and without coolant
4.12 Photomicrograph of Heat Affected Zone (HAZ) layer of mild steel above
74
(no coolant) and below (use coolant) .200X
4.13 Graph of comparison thickness of HAZ and depth of cut
75
4.14 Graph of comparison thickness of HAZ and feed rate
76
4.15 Graph of comparison thickness of HAZ between surface roughness
77
using coolant
4.16 Graph of comparison thickness of HAZ between surface roughness
78
without coolant
4.17 Influence of arrangement and number of cleaning nozzle on surface quality 79
14
during surface grinding (Marinescu, 2001)
4.18 Influence of different type of cooling lubricants on surface quality during
80
surface grinding (Marinescu, 2001)
4.19 Types of grinding wheel wear (Marinescu, 2001).
15
81
LIST ABBREVIATIONS
DOE
-
Design of Experiment
UTeM
-
Universiti Teknikal Malaysia Melaka
PSM
-
Projek Sarjana Muda
HSG
-
High Speed Grinding
ANSI
-
American National Standard Institute
ASTM
-
American Society for Testing and Materials
ISO
-
International Standard Organization
Ra
-
Roughness average
AA
-
Arithmetic average
CLA
-
Centre line average
Rz
-
Arithmetic mean
RMS
-
Root mean square
HAZ
Heat Affected Zone
16
CHAPTER 1
INTRODUCTION
1.1 Background
Grinding is one type of machining processes which utilizes hard abrasive particles as the
cutting medium. Grinding is traditionally regarded as a final machining process in the
production of components requiring smooth surfaces and fine tolerances. Nowadays,
grinding is a major manufacturing process which accounts for about 20-25% of the total
expenditures on machining operations in manufacturing countries (Malkin, 1998). When
compare grinding machine and lathe machine, there are many major different especially
type of operations. As we know, grinding machine is used to perform a grinding process.
The selection of the grinding process is depends on part shape and size, ease of fixturing
and the production rate required. Grinding operations are carried out with a variety of
wheel and workpiece configurations. The basic types of grinding operations are surface
grinding, cylindrical grinding, internal grinding and centerless grinding (Kalpakjian,
2001). Surface grinders are the largest percentage of user in manufacturing industries
compare with other type of process in grinding. For the lathe machine, it’s still known as
the oldest machine tools, simple and versatile machine. The operation process on the
lathe machine required a skilled machinist because all controls are manipulated by hand.
The type process can be done by lathe machines are turning, boring, drilling, milling,
planning, shaping, broaching and sawing.
The important aspect in selection of grinding machine is grinding wheel. The type of
grinding wheel used for a certain application can greatly influence the quality of
17
surfaces produced, as well as the economics of the operation. The selection process on
wheels not only the shape of wheel and part to be produce, but it also consider on
characteristics of the workpiece material as well. The grindability of materials consider
such as the quality of the surface produced, surface finish, surface integrity, wheel wear,
cycle time and overall economics. In manufacturing industries today, the using of
ceramics as grinding wheel increase relative ease using diamond wheel. The ability of
this wheel material is possible to produce continuous chips and good surface integrity in
grinding (Malkin, 1998). The ceramic chips sizes are typically 1 µm-10 µm (40µin400µin). There are also has another various type of materials that recommends for
grinding wheels like Aluminum, Brass, Bronze, Cast iron, Carbides, Ceramics, Copper,
Nickel alloys, Nylon, Steels, Titanium and Tool steels. These recommendations
materials vary significantly, depending on material composition, grinding operation and
grinding fluids used.
As equipment in manufacturing machining, grinding machine also has advantage and
disadvantage. The grinding machines are available for various workpiece, geometries
and size. But, for the lathe machine the workpiece with cylindrical shape only available
to be machining on lathe machine. In production, grinding machine now was completed
with computer controlled. It has features such as automatic workpiece loading and
unloading, clamping, cycling, gaging, dressing and wheel shaping. Beside that, grinders
also equipped with probe and gages for determining the relative position of the wheel
and workpiece surface. For the limitations of grinding machines, grinding requires much
energy than turning process. So, thermal and other damage to the workpiece surface is
more likely to occurred and cutting fluid is necessary than machine tool more expensive.
It is evident that the competitive position of hard turning verse grinding must be
evaluated individually for each application and in terms of product surface finish and
integrity, quality and overall economics.
For grinding mechanisms, High Speed Grinding (HSG) is one of the most popular
processes in manufacturing industries. To reduce the cycle time, high speed grinding is
needed for a certain process. High speed grinding has been used in certain process that
18
need to remove material as quickly and efficiently as possible with little concern for
surface quality. In gathering a good surface finish, grinding machining used in the
production and is important part of the machine tool trade to improved machine
construction has permitted the production of parts to extremely fine tolerances with
improved surface finish and accuracy of the finish product (Krar, 2006). In the HSG, the
parameter can be observed like surface roughness, speed, depth of cut and feed rate.
According to Kalpakjian (2001), increase the wheel speed, depth of cut and wheel
diameter will increase temperature. But, temperature decreases with increasing
workpiece speed. So, temperature rise in grinding is an important consideration because
it can adversely affect the surface quality and cause residual stresses on the workpiece.
19
1.2 Problems Statements
The quality of a machined surface is becoming more and more important in order to
satisfy the increasing demands of sophisticated component performance, longevity, and
reliability. An understanding of surface integrity provides much advantage in avoiding
failures, enhance component integrity and reduce overall costs. Although considerable
research has been done on high speed grinding, there is hardly any research following on
the AISI D2 cold work tool steel. Many researchers have shown that grinding process
can induce white layer. The presence of white layer in HSG and it causes still be a great
concerns in the machining industries and academia because the effect of the white layer
on a components service life has not yet been clarified as understood at present.
1.3 Objectives
The objectives of this research are:
i.
To study the influence of heat on the surface morphology in grinding process.
ii.
To find the significant machining parameters (depth of cut and feed rate) that
influence machining characteristics through (DOE).
iii.
To analyze the data from the experiment using MINITAB software.
20
1.4 Scope of Study
This research will involve experimentation by machining parts using surface grinding
machine in UTeM machine shop. The grinding parameter that had been used was feed
rate and depth of cut and the material that had been choose for this analysis is Mild Steel
AISI 1020. The process of the experiment had been analyzed under the process of using
coolant and without using coolant. After the machining process, all those specimens will
be analyzed by using the portable roughness measuring machine. The specimens will
also be analyzing using optical microscope for analyzing the effect of Heat Affected
Zone (HAZ). Besides, the result of the specimen microstructure will be compare with
microstructure of other specimens which by using differences parameter. The result of
surface roughness had also been analyzed by using Design of Experiment (DOE)
method. Through this method, the data is analyzed using the full factorial design.
21
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction to High Speed Grinding
High speed grinding is one type of process in manufacturing industries to reduce the
production time. It is required in a certain process and material. HSG could be an
economic strategy for achieving high efficiency in machining process. Applications of
high speed grinding have expanded the field of grinding from traditional finishing
operation to now more widely employed high-performance machining. In this way, high
performance grinding corresponds to the dual attributes of high efficiency and high
precision, which are required for competitive grinding processes.
HSG is characterized by efforts to improve the economics of the process by increasing
material removal rates and simultaneous improvements of process stability, capability
and machining quality (Kopac et al., 2006). Besides that, in technological terms HSG
refer to high productivity grinding in order to reduce the machining time while
maintaining the same level of quality and high quality grinding in order to enhance
machining quality while maintaining a constant machining capacity. As a theoretical, an
increase in wheel speed results in a reduction in maximum chip thickness and hence
grinding force which should promote ductile flow by reducing the tendency for brittle
fracture (Huang, 2002). In his research, Huang (2002) used Silicon nitride with resin
bond diamond wheel as a material. High wheel speeds will introduce other factors such
as vibration and wheel wear. In addition, the wheel speed and other grinding parameters
will be effect on the surface quality. Beside that, the effect of vibration by the
unbalanced wheel at high speeds will affect the surface roughness quality.
26
Surface grinding was employed in a down grinding mode. The effect on grinding
performance is caused by various wheel speeds, wheel depths of cut and feed rates.
According to Huang et al. (2001), he claims the lowest speed is 40m/s and the highest
speed is 80m/s and above. Increasing the wheel speed substantially reduced the
maximum chip thickness during grinding, which resulted in a lower grinding force
(Huang, 2002). In addition, it was also seen that the depth of cut had an importance
influence on the grinding force. A larger depth of cut led to a higher grinding force.
According to Huang (2002), it was found that higher grinding speed caused less
subsurface damage because a smaller grinding force was associated with the grinding
process. So, the application of high wheel speeds was useful to compensate for the
subsurface damage caused by high speed grinding and also has many advantages to
manufacturing industries.
2.1.1 Advantages of High Speed Grinding
High speed machining, like the grinding of hard materials at higher speeds increasingly
applied in the manufacturing industries. This technology is possible to execute final
machining operations without consequent grinding or similar finishing operations. This
machining process can produce high productivity, good surface finish quality and higher
dimensional tolerances. In this way, an increased cutting speed is prerequisite for
increased productivity. The tool life of high performance grinding wheels also increased.
The grinding tools for HSG are subjected to special requirements in terms of their
operational speed and resistance to wear and fracture (Kopac et al., 2006). Besides that,
high speed grinding more efficiently and can save production time. It is also suitable
used for finishing process. High sped grinding also can improve product quality in
combination with increased throughput and reduced production time. HSG can maintain
the machine tool reliability and in-process sensing product quality. Also, the increase in
the cutting speed is expected to cause a reduction in cutting forces (Bosheh et al., 2005).
27