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UNIVERSITI TEKNIKAL MALAYSIA MELAKA
EFFECT OF CUTTING PARAMETER ON ROUGHNESS
DURING SURFACE GRINDING OF INCONEL 718
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Manufacturing Process) (Hons.)
by
NURUL AFIZAN BINTI YAAKOB
B051110173
920606105002
FACULTY OF MANUFACTURING ENGINEERING
2015
UNIVERSITI TEKNIKAL MALAYSIA
MELAKA BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA
TAJUK: Effect of Cutting Parameter on Roughness during Surface Grinding of Inconel 718
SESI PENGAJIAN: 2014/15 Semester 2 Saya NURUL AFIZAN YAAKOB mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:
1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan
untuk tujuan pengajian sahaja dengan izin penulis. 3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan
pertukaran antara institusi pengajian tinggi.
4. **Sila tandakan ( )
SULIT
TERHAD
TIDAK TERHAD
(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia sebagaimana yang termaktub dalam AKTA RAHSIA RASMI 1972)
(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)
Alamat Tetap:
NO 39, Blok L,
Sungai Udang II,
41250 Klang, Selangor.
Tarikh: ________________________
Disahkan oleh:
Cop Rasmi: Tarikh: _______________________
** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai SULIT atau TERHAD.
DECLARATION
I hereby, declared this report entitled “Effect of Cutting Parameter on Roughness
during Surface Grinding of Inconel 718” is the result of my own research except as
cited in references.
Signature : ………………………………………………….
Author’s Name : ………..Nurul Afizan binti Yaakob……………
Date : ………….………………….…………………...
APPROVAL
This report is submitted to the Faculty of Manufacturing Engineering of UTeM as
a partial fulfilment of the requirements for the degree of Bachelor of
Manufacturing Engineering (Manufacturing Process) (Hons.). The member of the
supervisory is as follow:
………………………………………
(Dr. Mohd Shahir Kasim)
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ABSTRACT
Surface grinding is a finishing process where it will give the surface roughness of the
product lower than before. By this process, smooth surface can be produced. In order
to do this process, surface grinding machine is used. The parameters that are variable
in order to get the smoother surface roughness are traverse speed, depth of cut and
number of passes. The surface roughness is identified by using portable surface
roughness machine. The surface of the material look closer by using a stereo
microscope. In this experiment, there are 19 runs. Historical data under Response
Surface Methodology (RSM) is used to construct and analyze the data. Analysis of
variance (ANOVA) is used in order to look for the trend of the parameter towards the
surface roughness. After the analysis is done, the parameters can be known whether it
is significant or non-significant. A factor that is significant and not significant has been
identified. Traverse speed and depth of cut are significant factors while the number of
passes is not a significant factor in this experiment. A model is created after a trend
have been developed. In order to know whether the model is valid to use, validation
of the model is done. The number of errors produced is indicated whether the model
is valid or not. The model was valid as the error from actual value and predicted value
of surface roughness is 9.86%, which is less than the maximum acceptable error. The
future surface roughness can be predicted by insert the parameters into the model. The
optimum response were achieved by traverse speed of 9173 mm/min, depth of cut of
7 µm, and 10 number of passes. From this experiment, Inconel 718 can have low
surface roughness even though it is difficult to machine.
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ABSTRAK
Pengisaran permukaan adalah satu proses akhir di mana ia akan memberikan
kekasaran pada permukaan produk lebih rendah daripada sebelumnya. Melalui proses
ini, permukaan licin boleh dihasilkan. Bagi melakukan proses ini, mesin pengisaran
permukaan digunakan. Parameter yang berubah untuk mendapatkan kekasaran
permukaan yang licin adalah kelajuan mendatar, kedalaman pemotongan dan bilangan
laluan. Kekasaran permukaan dapat dikenalpasti dengan menggunakan mesin mudah
alih kekasaran permukaan. Permukaan bahan dapat dilihat dengan lebih dekat dengan
menggunakan mikroskop stereo. Eksperimen ini, terdapat 19 kali operasi. Data sejarah
di bawah Kaedah Sambutan Permukaan (RSM) digunakan untuk membina dan
menganalisis data. Analisis varians (ANOVA) digunakan untuk mencari arah aliran
parameter terhadap kekasaran permukaan. Selepas analisis dilakukan, parameter boleh
diketahui sama ada memberi kesan atau tidak. Faktor yang penting dan tidak penting
telah dikenal pasti. Kelajuan melintang dan kedalaman pemotongan adalah penting
manakala bilangan laluan adalah bukan faktor penting bagi eksperimen ini. Model
dicipta selepas arah aliran telah terhasil. Untuk mengetahui sama ada model itu adalah
sah untuk digunakan, pengesahan model dilakukan. Bilangan ralat yang terhasil
menunjukkan sama ada model itu adalah sah atau tidak. Model ini adalah sah kerana
ralat daripada nilai sebenar dan nilai ramalan kekasaran permukaan adalah 9.86%
dimana kurang daripada ralat maksimum yang boleh diterima. Kekasaran permukaan
boleh diramal dengan memasukkan parameter ke dalam model. Hasil optimum dicapai
dengan kelajuan melintang sebanyak 9173 mm / min, kedalaman pemotongan
sebanyak 7 μm, dan bilangan laluan adalah 10. Daripada eksperimen ini, Inconel 718
boleh mempunyai kekasaran permukaan yang rendah walaupun ianya sukar untuk
pemesinan.
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DEDICATION
To my beloved parents,
Yaakob Mohd Amin
Masrifah Haji Maskor
My beloved siblings,
Muhammad Asyraf Yaakob
Syaza Amirah Yaakob
Syarah ‘Afifah Yaakob
Muhammad Aizat Yaakob
Nurul Adiilah Yaakob
Muhammad Amirul ‘Adli Yaakob
Muhammad Arief Akmal Yaakob
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ACKNOWLEDGEMENTS
Praise to Allah as giving me to complete my PSM 1 and PSM 2. First of all, I would
like to thank my beloved parents, Yaakob Mohd Amin and Masrifah Haji Maskor for
their support and encourage. Hereby, gratitude to first and foremost, my PSM
Supervisor, Dr. Mohd Shahir Kasim for his supervision, guidance and information that
I had gained. Not forgotten, to all lecturers and staffs of Faculty of Manufacturing
Engineering, Universiti Teknikal Malaysia Melaka.
In addition, I wish to state my appreciation to those who helped me for their
contribution, especially to Encik Mazlan bin Mamat @ Awang Mat, assistant engineer
of machine shop laboratory and also, to Puan Siti Aisah Khadisah and Encik Mohd
Nazri Abdul Mokte, assistant engineer of metrology laboratory for their cooperation
and kindness. Last but not least, to all my course mates, BMFP batch 2011/2012 who
has been supporting me.
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1 TABLE OF CONTENTS
Abstract i
Abstrak ii
Dedication iii
Acknowledgements iv
Table of content v
List of figures viii
List of tables x
CHAPTER 1: INTRODUCTION 1
1.1 Introduction 1
1.2 Problem Statement 2
1.3 Objectives 3
1.4 Scope 3
1.5 Report Organization 4
CHAPTER 2: LITERATURE REVIEW 5
2.1 Surface roughness 5
2.2 Grinding Parameters 7
2.2.1 Depth of cut 7
2.2.2 Traverse speed 7
2.2.3 Number of pass 8
2.2.4 Wheel speed 8
2.3 Surface grinding machine 9
2.3.1 Type of wheel 11
2.3.2 Dressing 13
2.3.3 Coolant 14
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2.4 Material Used 17
2.5 Matrix of journal 18
CHAPTER 3: METHODOLOGY 20
3.1 Overview of the study 20
3.2 Machine, Apparatus and Equipment Used 23
3.2.1 Surface Grinding Machine 23
3.2.2 Portable Surface Roughness Machine 26
3.2.3 Stereo Microscope 27
3.3 Material Used 28
3.4 Software used 29
3.5 Determine factors that affect response 29
3.6 Select the factors to be analysed and the range of size to be used 30
3.7 Construct the experiment 31
3.8 Perform the experimental runs 32
3.9 Testing for significant 33
3.10 Analysed the result 34
3.11 Create a model 34
3.12 Validate the model 34
CHAPTER 4: RESULT AND DISCUSSION 35
4.1 Result of Experiment 35
4.1.1 Surface Roughness Test 35
4.2 Analysis of the Experiment 46
4.2.1 Analysis of variance 47
4.2.2 Traverse speed 48
4.2.3 Depth of cut 50
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4.2.4 Number of pass 52
4.3 Model creation 53
4.3.1 Validation 53
4.4 Optimization 54
CHAPTER 5: CONCLUSION 56
5.1 Conclusion 56
5.2 Recommendation 57
REFERENCES 58
APPENDICES 62
A Calculation of Traverse Speed.
viii
2 LIST OF FIGURES
2.1 Surface Characteristics and Terminologies. 6
2.2 Effect of increasing wheel speed a) at constant removal rate and
b) at increasing removal rate (Rowe, 2009).
9
2.3 Material removal as workpiece the grinding wheel in down-cut
grinding (Rowe, 2009).
10
2.4 Roughing, ploughing, and cutting at different grain penetration
through the arc of contact (Rowe, 2009).
11
2.5 Aluminium oxide grinding wheel. 12
2.6 Single-point dressing (Rowe, 2009). 14
2.7 Function of the fluid (Source: Rowe, 2009). 15
2.8 Traditional nozzle 17
3.1 Flow Chart 22
3.2 Surface Grinding Machine 23
3.3 Surface roughness produced by common production methods
(Vorburger & Raja, 1990).
25
3.4 Portable surface roughness machine 26
3.5 Stereo microscope 27
3.6 Specimen of Inconel 718 28
3.7 Peripheral surface grinding (Rowe, 2009). 33
4.1 Graph of surface roughness for pick and feed directions 37
4.2 Surface of run number 1 with surface roughness of 1.169 µm 39
4.3 Surface of run number 2 with surface roughness of 1.822 µm 39
4.4 Surface of run number 3 with surface roughness of 2.350 µm 39
4.5 Surface of run number 4 with surface roughness of 1.343 µm 40
4.6 Surface of run number 5 with surface roughness of 0.863 µm 40
4.7 Surface of run number 6 with surface roughness of 1.680 µm 40
4.8 Surface of run number 7 with surface roughness of 0.973 µm 41
4.9 Surface of run number 8 with surface roughness of 0.988 µm 41
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4.10 Surface of run number 9 with surface roughness of 1.780 µm 41
4.11 Surface of run number 10 with surface roughness of 0.955 µm 42
4.12 Surface of run number 11 with surface roughness of 1.746 µm 42
4.13 Surface of run number 12 with surface roughness of 1.814 µm 42
4.14 Surface of run number 13 with surface roughness of 0.893 µm 43
4.15 Surface of run number 14 with surface roughness of 0.945 µm 43
4.16 Surface of run number 15 with surface roughness of 1.677 µm 43
4.17 Surface of run number 16 with surface roughness of 0.864 µm 44
4.18 Surface of run number 17 with surface roughness of 1.115 µm 44
4.19 Surface of run number 18 with surface roughness of 2.333 µm 44
4.20 Surface of run number 19 with surface roughness of 3.012 µm 45
4.21 Graph of diagnostic case statistics 48
4.22 Graph of inverse square root of surface roughness against
traverse speed
49
4.23 Graph of inverse square root of surface roughness against depth
of cut
50
4.24 Illustration of depth in workpiece 51
4.25 Graph oh inverse square root of surface roughness against
number of pass
52
x
3 LIST OF TABLES
2.1 Recommendation to select abrasives (Kalpakjian & Schmid,
2014)
12
2.2 General recommendations for grinding fluids (Kalpakjian &
Schmid, 2014)
16
2.3 Grinding fluid characteristics (Webster et al., 1995) 16
2.4 Properties of Inconel 718 17
2.5 Matrix of journals 18
3.1 Gantt chart 21
3.2 Specification of surface grinding machine 24
3.3 Standard of surface roughness measurement 27
3.4 Chemical composition of Inconel 718 (Mankar & Jadhav, 2007). 28
3.5 Physical and mechanical properties of Inconel 718 (Shokrani et
al., 2012)
29
3.6 Parameter used and its range 30
3.7 Run of experiment 31
4.1 Readings of surface roughness on pick direction 36
4.2 Readings of surface roughness on feed direction 36
4.3 Calculation of Surface Roughness 38
4.4 Result of experiment 46
4.5 Analysis of variance 47
4.6 Parameters for validation 53
4.7 Parameters for optimization. 54
4.8 Calculation of the reading of surface roughness 55
1
1 CHAPTER 1
INTRODUCTION
1.1 Introduction
Grinding is a chip-removal process that uses an individual abrasive grain as the cutting
tool (Kalpakjian & Stevent, 2014). Rowe (2009) defined that grinding is a term used
in modern manufacturing practice to describe machining with high-speed abrasive
wheels, pads, and belts. In other word, grinding is a machining process that employs
an abrasive grinding wheel rotating at high speed to remove material from a softer
material (Marinescu et al, 2006). It is one of the last steps in machining operation chain
and highly developed to particular product and process requirement. In this study,
surface grinding machine is used.
Aslan and Budak (2014) stated that grinding can be a cost effective alternative even
for roughing operations of some hard-to-machine materials. It is important to know
the relation between input parameter and its response or output characteristic. Input
parameter that usually researcher vary it are speed, feed rate, depth of cut, type of
wheel, grit, usage of coolant and force. In this study, three parameters are vary which
are traverse speed, depth of cut and number of passes.
The output or the response that is going to study is the surface roughness of the
material. Surface roughness is choose as the response because, it is one of the quality
measures, especially in industry of manufacturing (Davim, 2010). In the shop floor,
the usual practice is to allocate to the grinding process the most experimented
operators, who use their experience to take decisions related to the process (Hassui &
Diniz, 2003). Moreover, the machining conditions used play a key role in deciding the
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surface quality (Mankar & Jadhav, 2007). This shows that the surface quality is not
easily predicted by its parameter.
1.2 Problem Statement
Surface grinding is one of the final steps that is used to surface finish of the product.
This because, the product that was not done by finishing process will result bad surface
roughness. It is important for the product to get the desired surface roughness as to
improve the quality of product and survive in industry (Whitehouse, 2004). By
choosing survival in industry, it will give a good opportunity to suggest the result and
applied it in industry. Choosing problems that can give result that have merit (Alon,
2009).
In this study, Inconel 718 which is Nickel base alloy is the material of specimen. This
type of material is not only has high strength, fatigue resistance, corrosion resistance,
and heat resistance, but also possesses lower thermal conductivity (Tso, 1995b). This
type of material has a wide variety of particular purposes. It is mainly applied in
reciprocating engines, stack gas reheater and aircraft gas turbines. However, Nickel-
base super alloy, Inconel 718, is generally known to be one of the most difficult
materials to machine because of its high hardness, high strength at high temperatures
(Nalbant et al, 2007). Machinability is refer to the work material being machined in
ease way under a given set of cutting parameters conditions where the main parameters
of machinability assessment are surface roughness, cutting force and tool life
(Choudhury & El-Baradie, 1999).
There will be several effect to the sample which grind with one type of grinding wheel.
The purpose of this research is to find the good parameter that can produce optimum
effect on the surface roughness of Inconel 718. Due to the hardness of the Inconel 718
with the type of grinding wheel, depth of cut will affect the surface roughness (Ulutan
& Ozel, 2011). This research also develop to know the best feed rate that will give the
best surface roughness. At the end of this study, a model can be created based on the
experimental run. There are narrow attention on grinding process of Inconel 718.
3
Understanding the behaviour of Inconel 718 in the grinding process is vital importance
as it is limited attention on machinability of Inconel 718 (Tso, 1995b).
1.3 Objectives
While grinding, there will be changes in surface roughness of Inconel 718 due to
different parameter used. There are three objectives that will be executed which are:
a) To identify the significant and non-significant factors that affect surface roughness
on Inconel 718.
b) To identify the optimum parameter which affect surface roughness of Inconel 718.
c) To develop a mathematical model of surface roughness.
1.4 Scope
Surface grinding machine is used in order to grind the surface of the material. The
material that is going to be grind is Nickel base alloy which is Inconel 718. The sample
size of the material is 123 x 31 x 30 mm. Traverse speed, depth of cut and number of
pass is vary in order to find significant and non-significant factor of surface grinding.
Design of Experiment (DOE) is used to design the experimental run. By using Design
Expert software, this research applies the historical data approach which is under
response surface methodology to study the surface roughness. The surface roughness
is measured from the surface grinding machine. 19 experimental run is construct in
order to analyse the trend of the surface roughness. Each of the variable parameter is
vary in three values. The values are decided by previous study and the range of
parameter that the machine can handle. The parameter input that is constant for every
experiment are type of wheel and coolant used. Type of wheel that is used is aluminium
oxide (Al2O3) while the type of coolant is Synkool 300G which is synthetic water
soluble coolant.
4
In order to identify its surface roughness after it is grind on its parameter, portable
surface roughness machine is used. Arithmetic mean value, Ra is used which the
standard is Jis 94. In order to look closer on the surface topography, stereo microscope
is used. Data collected is then be analysed by analysis variance (ANOVA).
If there is a void on the surface of the material after grind, the size of the void is not
going to be measured. The chip formation also will not be analyse. The attention is
more on its surface roughness.
1.5 Report Organization
This report consist of five chapters. First chapter is explaining about the background
of the study and problem statement which develop objectives and scope.
Second chapter is revolve on literature review from journal, books and web sites that
related to the surface roughness of Inconel 718. It also include the parameters that will
affect the surface roughness. At the end of this chapter will include summary of sum
previous research related to this study.
Third chapter explaining about the method used to execute the experiment. Apparatus,
tools, software and material used in the experiment also explain in this chapter. The
design of experiment was also explained in this chapter.
In chapter four, the result obtain from the experiment are shown. Analysis from the
result also included in this chapter. The discussion which is the explanation from the
result also discussed in this chapter.
The last chapter which is chapter five is the conclusion for the whole experiment. The
result from the achievement of objective is concluded.
5
2 CHAPTER 2
LITERATURE REVIEW
2.1 Surface roughness
Surface roughness is a component of surface texture. Surface roughness, not
surprisingly, is closely related to uncut chip thickness (Marinescu et al., 2006). In other
word, roughness is defined as narrowly spaced, uneven deviations on a small scale; it
is expressed in terms of its width, height and distance along the surface (Kalpakjian &
Stevent, 2014). There are two methods of surface roughness which are arithmetic mean
value (Ra) and root-mean-square roughness (Rq). The arithmetic mean value is based
on the schematic illustration of a rough surface and defined as (Hashimoto et al., 2012):
𝑅𝑎 =
𝑎 + 𝑏 + 𝑐 + 𝑑 + ⋯
𝑛
(1)
Where all ordinates a, b, c, …, are absolute values and n is the number of readings. In
the other hand, root-mean-square roughness is defined as
𝑅𝑞 = √
𝑎2 + 𝑏2 + 𝑐2 + 𝑑2 + ⋯
𝑛
(2)
The unit of surface roughness generally used micro meter, (µm). Figure 2.1 shows the
surface characteristics that the roughness is measured. The figure shows a surface that
has been produced by some machining process. There are two orders of structure. The
roughness with its typical roughness spacing and roughness height represents the more
6
narrowly spaced peaks and valleys. Usually, roughness is produced by the basic
process of surface forming.
The pick direction measurement is measure on the waviness of the surface. It consists
of broadly spaced irregularities and is often produced by vibrations in the machine. In
the other hand, feed direction is measure on the lay. Term lay is used to represent the
direction of the dominant pattern of texture on the surface. Machining processes that
produced surfaces ordinarily have a strong lay pattern (Vorburger & Raja, 1990).
Figure 2.1: Surface Characterisrics and Terminologies (Vorburger & Raja, 1990).
Surface integrity is important in manufactured products as it affects various properties
of the manufactured parts like corrosion rate, stress corrosion cracking, wear, fracture
toughness magnetic properties and dimensional stability (Demir et al., 2010).
7
2.2 Grinding Parameters
Grinding is different from turning and milling processes. It is important to know the
grinding parameter in order to understand on how process adjustments change cycle
time, part quality and wheel performance. Usually, it is quite limited in understanding
the number of grinding parameters. Surface roughness is affected by wheel speed,
traverse speed, feed rate, type of workpiece, depth of cut, type of wheel, and other
parameter (Razali, 2010).
2.2.1 Depth of cut
Depth of cut is the most basic grinding parameter. Depth of cut is the depth of material
removed per revolution or table. The real depth of cut ae is the depth of cut that has
been cut by grinding process. Typically, real depth of cut is approximately a quarter
of programmed depth of cut ap depending on the workpiece hardness (Rowe, 2009).
Based on Singh et al (2014), depth of cut is the most significant parameter that effect
the surface roughness. It can be said that, the higher the depth of cut, the higher the
surface roughness. Furthermore, the increase in depth of cut will increased the
maximum chip thickness which resulted in poor surface quality (Shokrani et al., 2012).
Moreover, lower depth of cut resulted lower surface roughness, while higher depth of
cut resulted in higher values of surface roughness due to the higher values of peaks
height (Arunachalam et al., 2004).
2.2.2 Traverse speed
Grinding operations considered two dimensional motions in a common plane which
are wheel and workpiece motions. The equivalent terms of work speed are traverse
speed and table speed (Marinescu et al., 2006). Traverse grinding involves the addition
of cross feed which is traverse motion of the grinding wheel relative to the workpiece
in a direction perpendicular to the plane of the wheel rotation (Malkin & Guo, 2008).
8
The workpiece metal will be stick by magnetic worktable of surface grinding machine.
However, Inconel 718 is not magnetize, therefore clamping mechanism is used to
attach the workpiece. If the traverse speed is different, the surface roughness of the
workpiece will also be different. The surface roughness increases with decreasing
grinding wheel speed and increasing table speed and down-feed (Tso, 1995b). By
increasing the traverse speed, the surface roughness will also increase (Shokrani et al.,
2012). This because, reduce work speed will reduce waviness (Drive, 2007).
2.2.3 Number of pass
Grinding process is different from other process like turning and milling as it can do
in two ways which are in single stage or multi-pass grinding. By applying multi-pass
grinding, the surface roughness can be improved and better than single stage. The
single of grinding process did not give the surface roughness as smooth as multi-pass
grinding (Azizi, 2008). Therefore, number of passes is considered as variable
parameter in this study.
2.2.4 Wheel speed
The higher the grinding speed, the lower the forces and surface roughness that allowing
higher removal rate. The advantages of high-speed grinding are high productivity,
accuracy and quality. It also will reduce manufacturing complexity and improve
process reliability. By applying high-speed grinding, it will result better integrity,
better accuracy, faster machining and high-efficiency grinding (Rowe, 2009).
The effect of increasing the speed of wheel with constant work speed and depth of cut
will result low material removal rate by each grain. Surface roughness, grinding force,
and wheel wear are also reduced (Rowe, 2009). In the other hand, the effect of
increasing wheel speed with increasing material removal rate in directly proportional
will result constant grinding force, roughness and wheel wear. Figure 2.2 shows the
effect of increasing wheel speed for both situation.
9
Figure 2.2: Effect of increasing wheel speed a) at constant removal rate and b) at increasing removal
rate (Rowe, 2009).
2.3 Surface grinding machine
Grinding process will composed of chip formation. At the very first stage of the
interaction between abrasive grit and the workpiece, plastic deformation occurs,
temperature of the workpiece increases and let normal stress to exceed yield stress of
the material (Aslan & Budak, 2014). After a certain point, abrasive grit starts to
penetrate into the material and starts to displace it, which is responsible for the
ploughing forces. Finally, grit starts to shearing action and removes the chip from
workpiece (Aslan & Budak, 2014). Factor of applying grinding process is because of
it gives high accuracy. Furthermore, high removal rate that is required by the material
can be applied by grinding process. Machining of hard materials is also one of the
factor that grinding process is applied (Marinescu et al., 2006).
Rowe (2009) identify that the input for grinding process are speeds, feeds, tools,
materials, labour, energy and cost. Grinding process also has disturbances which will
affect the output of the process. The disturbances are vibrations, tool shape errors,
static deflections, initial workpiece shape, temperature flactuations and machine
errors. By present of those disturbances, the output will be affected. This will result,
10
inaccurate value. Therefore, it is important to run the experiment in condition of absent
or minimum disturbance.
The productive outputs are shape and accuracy, machined parts, production rate,
surface integrity and surface texture. Surface texture is the nature of a surface as
defined by the three characteristics which are lay, surface roughness and waviness.
The small local deviations of a surface from the perfectly flat ideal is comprise. In the
other hand, surface condition of a workpiece after being modified by a manufacturing
process where it change the properties of the material is the surface integrity. There
are also non-productive outputs which are waste fluid, noise, tool wear, swarf, heat,
and mist (Rowe, 2009). Those non-productive outputs are produce during or after
grinding process.
Down-cut is one of the grinding process. The advantages of conventional down-cut
grinding are its surface roughness and reduced wheel wear as the force tend to be lower
(Rowe, 2009). There will be material removal in down-cut grinding as shown in Figure
2.3. There are three stages of metal removal which are rubbing, cutting and ploughing.
Some grains rub without ploughing. There also some grains plough without cutting
and some grains experience all three stages. It is depending on increasing depth of
grain penetration into the surface (Rowe, 2009). Figure 2.4 shows rubbing, ploughing
and cutting through the arc of contact.
Figure 2.3: Material removal as workpiece the grinding wheel in down-cut grinding (Rowe, 2009).