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PERPUSTAKAAN UTHM
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CATAT A'\: •. Potong yang tidal: berkenaan >0, Jika tesis ini SCUT atau TIRI-L-ill. sila Iampirkan surat daripada pilw: + berkuasa organisasi berk enaan dengan m enyatal:an sebli sebab dan tem poh tesi s ini
perJu dike1askan sebagai Sl1.IT atau TIRE.-ill Tesis dim al: sudk an sebagai tesis bagi Ij a:ah Doktor Falsafah chn S arjana secara penyelidi1-:an, atau disertasi bagi pengajian seeM kerja l:ursus dan penye1idi1-:an. atau
L aporan Projek S <llj all a ~:uda (PS~7)
"I hereby declare that I have read this thesis and in my opinion this thesis
is sufficient in terms of scope and quality for the award of the degree of Master in
Mechanical Engineering"
, Signature
Supervisor
Date
INFLUENCE OF ELECTRICAL PARAMETERS AND OPTIMIZATION
OF EDM PERFORMANCE MEASURES ON Ti-6AI-4V
USING DOErr AGUCHI METHOD
MOHD ZAHIRUDDIN B MD ZAIN
This thesis is submitted as a fulfillment of the requirements for the award of the degree
of Master in Mechanical Engineering
Faculty of Mechanical and Manufacturing Engineering
Kolej Universiti Teknologi Tun Hussein Onn
DECEMBER, 2005
II
"1 declare that this thesis entitled "Influence of Electrical Parameters and
Optimization of EDM Performance Measures on Ti-6AI-4V Using DOEffaguchi
Method" is the result of my own research except as cited in references. The thesis has
not been accepted for any degree and is not concurrently submitted in candidature of any
degree".
Signature
Name of Candidate : Mohd Zahiruddin B Md Zain
Date o \.- \ 1- - ::LO 0 S
Ulltuk isteri
dall allak-allak
yallg mellceriakall sllasalla,
mak dall abalz serta keillarga yang memberi sokollgall
1lI
PENGHARGAAN
Saya ingin mengucapkan ribuan terima kasih kepada
Dr Sulaiman Hj. Hasan
selaku penyelia dan banyak membantu dalam perlaksanaan projek ini.
Ucapan terima kasih juga kepada
En. Amri, En. Erween, En. Kamaruddin
serta abang-abang juruteknik;
Zharul, Faizal, Tarmizi, Rahman dan Adam
di atas sokongan dan bantuan anda.
Juga terima kasih kepada pensyarah-pensyarah di:
KUiTTHO, UTM dan UKM
yang mengajar dan mendidik saya sepanjang kursus di KUiTTHO.
Seterusnya ucapan terima kasih kepada staf-staf:
PPS, FK.MP khasnya serta KUiTTHO amnya.
HANY A ALLAH DAP AT MEMBALAS
KEIKHLASAN YANG TELAH
ANDA CURAHKAN
IV
\.
ABSTRACT
Advanced materials such as Titanium Alloys exhibit very excellent technical
properties, however have only achieved partial acceptance in industrial application due
to difficulties in machining. Advanced machining process such as Electrical Discharge
Machining (EDM) is a potential process to machine such materials. However, lack of
infonnation regarding machining process of those materials using EDM is a major
constraint. In this work Channilles Technology Robofonn 100 die-sinking EDM was
utilized to perfonn the machining of Ti-6AI-4 V and copper was used as the tool
electrode. The focus of this work is the optimization of the EDM process variables
where electrical parameters namely; intensity (I), pulse duration (Ii), pulse-off time (to)
and open circuit voltage (U) were set as design factors. The effect of these design factors
on EDM perfonnance measures or responses such as Material Removal Rate (MRR),
Volumetric Electrode Wear Rate (EW) and surface roughness average (Ra) were studied
and the optimum conditions and values of those responses were estimated. Beside that,
the overall evaluation criteria (OEC) which represents all three responses into single
index were also proposed at the finishing stage. Finally confinnation tests were
conducted to verify the estimated values and all the experimental results fall within 10%
error. Taguchi approach Design of Experiment (DOErraguchi) was utilized from
planning until analyzing the results and to assists this work, DOE software; Qualitek 4
was utilized.
VI
ABSTRAK
Bahan tennaju seperti aloi Titanium mempunyai sifat-sifat teknikal yang sangat
baik, tetapi penerimaanya agak kllrang dalam industri disebabkan oleh kesukaran dalam
proses pemesinan. Mesin tennaju seperti Mesin Nyahcas Elektrik (EDM) merupakan
proses yang berpotensi untuk memotong bahan-bahan tersebut. Halangan utama ialah
kurangnya infonnasi berkenaan proses pemotongan bahan-bahan terse but menggunakan
EDM. Dalam projek ini Channilles Technology Robofonn 100 die-sinking EDM telah
digunakan untuk memesin Ti-6A1-4V dengan kuprum sebagai mata alat. Fokus dalam
projek ini adalah pengoptimaan pembolehubah proses EDM di mana parameter elekirik
iaitu arns puncak (I), tempoh denyutan (Ii), tempoh tanpa denyutan (to) and voltan litar
terbuka (U) telah diset sebagai fakior. Kesan fakior-faktor ini ke atas pencapaian EDM
iaitu kadar pmbuangan bahan (MRR), kadar kehausan isipadu mata alat (EW) dan purata
kekasaran pennukaan (Ra) telah dikaji dan kombinasi serta nilai optima bagi setiap
pencapaian telah dianggar. Selain itu, kriteria penilaian keseluruhan (OEC) yang
mewakili kesemua riga pencapaian dalam satu indeks juga dicadangkan pad a peringkat
penyudah. Akhir sekali, ujian pengesahan telah dijalankan untuk pengesahan nilai
anggaran dan semua nilai ujian eksperimen jatuh dalam lingkungan 10% ralat. Taguchi
approach Design of Experiment (DOE/Taguchi) telah digunakan dari perancangan
sehingga ke peringkat penganalisaan dapatan kajian dan bagi membantu projek ini
peri sian DOE; Qualitek 4 telah digunakan.
VB
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDIKASI iii
PENGHARGAAN iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xiii
LIST OF SYMBOLS xiv
LIST OF APPENDICES xvii
I INTRODUCTION 1
1.1 Research Background 2
1.2 Problem Statement 3
1.3 Research Objective 4
1.4 Scope of Work 4
1.5 Definition 5
Vlll
IT LITERA TURE REVIEW 7
2.1 Titanium Alloy Machining 8
2.1.1 Ti-6AI-4V 8
2.1.2 Ti-6Al-4V Machining 9
2.2 Electrical Discharge Machining (EDM) 11
2.2.1 EDM System 11
2.2.1.1 Electrode 11
2.2.1.2 Power Supply 13
2.2.1.3 Servo system 13
2.2.1.4 Dielectric 14
2.2.2 EDMProcess 15
2.2.3 EDM Research Area 18
2.2.3.1 Major Areas 18
2.2.3.2 Focus Area 22
2.2.4 EDM Responses 23
2.2.4.1 Material Removal 24
2.2.4.2 Tool Wear 25
2.2.4.3 Surface Quality 26
2.2.5 Design Factors 27
2.2.5.1 Intensity 28
2.2.5.2 Pulse Duration 28
2.2.5.3 Pulse-Off Time 29
2.2.5.4 Open Circuit Voltage 29
2.2.6 Design Factors Effects over Reponses 30
2.2.6.1 General Effects 30
2.2.6.2 Effects over MRR 33
2.2.6.3 Effects over EW 34
2.2.6.4 Effects over Ra 35
2.2.6.5 The Summary of Design Factors Effect 35
2.3 DOE/Taguchi 37
IX
2.3.1 Introduction 38
2.3.1.1 Quality Characteristic 38
2.3.1.2 Overall Evaluation Criteria 39
2.3.1.3 Orthogonal Arrays 40
2.3.1.4 MSD and SIN Analysis 42
2.3.2 Representing Multiple Responses into Single Index 44
2.3.3 ANOVA 46
2.3.3.1 Average Factor Effect 48
2.3.3.2 Optimum Condition 50
2.3.3.3 Estimated Performance at Optimum
Condition 50
2.4 Literature Review Summary 51
ill METHODOLOGY 53
3.1 Introduction 53
3.2 Overview of the Methodology 54
3.3 Equipment 56
3.3.1 EDM System 56
3.3.2 Weight Measurements 57
3.3.3 Surface Roughness Measurement 58
3.4 Literature Review 59
3.5 Planning the Experiment 60
3.5.1 ClarifY the Project Objectives 60
3.5.2 ClarifY the Design Factors 61
3.5.3 Determine the Number of Levels 62
3.5.4 Describe the Experiments 63
3.6 System Setting and Programming 64
3.7 Electrodes Preparation 66
3.7.1 Copper Tool Electrode 66
IV
v
VI
3.8
3.7.2 Ti-6AI-4V Workpiece
Conduct the Experiments
RESULT ANALYSIS AND DISCUSSION
4.1 Introduction
4.2 Experimental Result
4.3 Result Analysis
4.3.1 Average Factor Effects
4.3.2 ANOVA Table
4.3.3 Predicted Optimum Condition & Confirmation Test
4.4 Discussion
4.4.1 Effect of Design Factors over MRR
4.4.2 Effect of Design Factors over EW
4.4.3 Effect of Design Factors over Ra
4.4.4 Effect of Design Factors over OEC
4.4.5 Optimum Condition
CONTRIBUTION AND RECOMMENDATION
5.1
5.2
Contribution of this Work
Future Work Recommendation
CONCLUSION
REFERENCES
APPENDICES
67
68
69
69
70
73
73
76
78
79
80
82
84
86
88
89
89
90
91
93
96
x
Xl
LIST OF TABLES
TABLE NO. TITLES PAGE
2.1 Chemical Composition of Ti-6AI-4V (v.1. %) 9 2.2 Mechanical Properties of Ti-6Al-4V 9 2.3 Typical Range for EDM Perfonnance Measures 23 2.4 Summary of Factors Effects over Responses 36 2.5 Full-Factorial Experiments 41 2.6 Number of Combinations 41 2.7 General EDM Perfonnance for Ti-6AI-4V (finishing
45 operation)
2.8 OEC for Each Trial 46 2.9 Experimental Design Array with Results for EDMed TI-6Al-
48 4V
2.10 Literature Summary 52 3.1 Levels of Design Factors 62 3.2 Experiments Layout 63 3.3 Robofonn 100 Generator Setting Table 64 3.4 Robofonn 100 Generator Setting Code 64 3.5 Constant Input Parameters 65
4.1 Experimental Results for MRR 71
4.2 Experimental Results for EW 71
4.3 Experimental Results for Ra 72
4.4 Experimental Results for OEC 72
4.5a Average Effects of Factors (SIN Ratio ofMRR) 74
4.5b Average Effects of Factors (MRR average) 74
4.6a Average Effects of Factors (SIN Ratio ofEW) 74
4.6b Average Effects of Factors (EW average) 74
XII
4.7a Average Effects of Factors (SIN Ratio ofRa) 75
4.7b Average Effects of Factors (Ra average) 75
4.8a Average Effects of Factors (SIN Ratio of OEC) 75
4.8b Average Effects of Factors (OEC average) 75
4.9 Analysis of Variance (ANOVA) for MRR 76
4.10 Analysis of Variance (ANOVA) for EW 76
4.11 Analysis of Variance (ANOVA) for Ra 77
4.12 Analysis of Variance (ANOVA) for OEC 77
4.13 Optimum Conditions and Values 78
xiii
LIST OF FIGURES
FIGURE NO. TITLES PAGE
2.1 Relaxation Circuit 15
2.2 Different of Waveform Between Both Types of Generator 16
2.3 Classification of Major EDM Research Areas 18
2.4 Relation ofEDM Major Research Areas 21
2.5 Effect of Current on EDM Process 31
2.6 Effect of Spark Frequency on Surface Finish 31
3.1 Methodology Overview and Result 55
3.2 Roboform 100 56
3.3 Electronic Balance 57
3.4 Surface Roughness Measuring Set 58
3.5 Copper Tool Electrode 66
3.6 Ti-6AI-4V Worh.rpiece 67
4.1a Multi-plot of Average Factors Effect over MRR 81
4.1b Factors Influence Percentage over MRR 81
4.2a Multi-plot of Average Factors Effect over EW 83
4.2b Factors Influence Percentage over EW 83
4.3a Multi-plot of Average Factors Effect over Ra 85
4.3b Factors Influence Percentage over Ra 85
4.4a Multi-plot of Average Factors Effect over OEC 87
4.4b Factors Influence Percentage over OEC 87
AC
Al
ANOVA
B4C
C CF
CNC
DC DOE
DOElTaguchi
DOF El~E9
EDM
EW
EWR
EWV EWW
f F fl
FI
HAZ HMP
I Ii m
Mn Mo
MRM MRPI
LIST OF SYMBOLS
Alternating current
Aluminum
Analysis of variance
Hot-pressed boron carbide Condenser
Correction factor
Computer Numeric Control
Direct current Design of experiment
Taguchi approach DOE
Degree of Freedom
Experiments conditions ] through 9 Electrical Discharge Machining
Volumetric Electrode Wear Rate
Electrode wear ratio
Tool electrode wear volume (mm3)
Tool electrode wear weight (g)
DOF of the factor F-ratio
DOF of the factor I F-ratio for factor I Heat affected zone Hybrid Machining Process
Intensity Total result at level i of! (i=l, 2, 3) Total number of average effect
Manganese
Molybdenum Material removal mechanism Multiple-response performance index
XIV
xv
MRR Material Removal Rate MSD Mean-squared deviation
N Total number of result Ni Number of result at level i of! (i=l, 2, 3)
OEC Overall evaluation criteria P Factors influence percentage P Percentage influence of factor
Pc Peak count or peak density PMD-EDM Powder-mixed dielectric
QC Quality Characteristic QC=B Bigger is better QC=N Nominal is the best QC=S Smaller is better
Ra Roughness average RC Relaxation circuit RF Radio Frequency Rq Roughness quadratic average
S The factor sums of squares S' The pure sum
SIN Signal-to-noise ratio SI' The pure sum for factor I
SiSiC Reaction-bonded silicon carbide Sm Mean spacing of profile irregularities SR Surface roughness ST The total sum of squares
T Machining time in minute T Total of results ti Pulse Duration to Pulse-off Time
TWP Tool wear process TWR Tool wear ratio
U Open Circuit Voltage V Vanadium V Variance
Vc Potential difference across the condenser Ve Variance for the error Vg Breakdown potential of the spark gap VI Variance for factor I Vs Supply voltage
VTW Volumetric tool wear WC-Co Cobalt-bonded tungsten carbide
WRV
WRW
Yi
'1 P T
C
o
Workpiece removal volume (mm3)
Workpiece removal weight (g)
Result at trial i (i = 1, 2 ...... 9)
Duty Cycle
Density
Grand Average
Total Contribution
Predicted Optimum Value
XVI
XVll
LIST OF APPENDICES
APPENDIX NO. TITLES PAGE
A Common Orthogonal Arrays 96
B 4 Three-Level Orthogonal Arrays 97
C Simple Arithmetic Calculation 98
D ANOV A Calculation 106
E MSD and SIN Ratios 110
F Titanium Alloys 112
G Main Effects of Design factors over Responses 117
1
CHAPTER I
INTRODUCTION
There are many advanced materials such as Titanium Alloys which exhibit very
excellent technical properties that have been invented. However, these materials have
only achieved partial acceptance in industrial application due to difficulties in machining
especially when utilizing conventional machine. Therefore, advanced machining such as
Electrical Discharge Machining (EDM) are normally used.
Since 1950s, EDM is one of the most extensively used advanced material
removal processes. The capability in machining extremely hard material is the main
advantage of this system. The non-contact machining technique is a characteristic of
EDM that reduces mechanical stresses, chatter and vibration during machining.
However, there is no universal criterion regarding machining condition for all
electrodes combinations. Therefore, in this work information regarding Titanium alloy
machining using EDM has been obtained. For this purpose optimizing process variables
ofEDM process are the main focus.
There are multi variables involve while utilizing EDM and design of experiment
(DOE) is appropriate method for this situation. In this work Taguchi approach DOE
(DOE/Taguchi) was used to study the influence of electrical parameters over EDM
responses simultaneously.
2
1.1 Research Background
Advanced materials such as Titanium Alloy exhibit very excellent teclmical
properties especially in term of strength, hardness and touglmess. These materials are
suitable in either macro components such as in aerospace and automotive industries or
micro components such as in electronic industries. These industries depend increasingly
on higher geometric accuracies and micro or nano structured surfaces to meet the
growing need for improve performance and reliability. However, it is partially
acceptable in industrial application due to difficulties in machining especially when
utilizing conventional machining. Therefore, for many industries the above requirements
is leading to capabilities of conventional machining methods and machine tools being
eclipsed by new processes and machine systems which currently at the research stage [4],
[24]. Furthermore, the advances in the field of EDM have permitted the application of
this technology to the manufacture ofthose materials [4].
High precision manufacturing has become a strategic and globally competitive
issue for a wide range of high teclmology products in the mechanical and electronic
industries. In order to increase global competitiveness it is essential to have the ability to
manufacture critical components with increasingly higher precision. The importance to
manufacture products with higher precision has been demonstrated by Japanese through
its dominance of many markets with advance technology and high quality products,
made possible by higher precision capabilities. Another critical aspect of high precision
manufacturing is the trend towards miniaturization [24].
Therefore, information regarding machining process of new materials usmg
advanced machining including EDM process is important. For this purpose, optimizing
process variables is one of the major EDM research areas [22]. Furthermore, result of
optimal condition is unique for every combination of different materials of tool electrode
and workpiece. Once the parameters of the model have been determined experimentally
for a given workpiece and tool, the model should be able to give reliable predictions
under various process conditions [14], [15].
3
Repeating the same research and usmg the same electrodes combination is
meaningless unless an improvement is added for better performances. However,
research on combination of electrodes that was never done before is important as a basis
for improvement and comparison by other researcher or for future research. For example
improvements that can be added are powder-mixed dielectric EDM (PMD-EDM),
oxygen assisted machining and carbon layered tool [22].
Although many aircraft industries use EDM for Titanium Alloys machining, not
much work has been reported regarding their machining conditions. Furthermore, there
is no standard teclmology for reference and there is no teclmical data available [29].
Currently, there is also no specific research regarding optimizing EDM process variables
between Ti-6Al-4V and Copper tool combination. Thus, this work is will be the basis
and reference for improvement research of particular combination in future.
1.2 Problem Statement
1. How do electrical parameters applied in this work influence the EDM
performance for machining Ti-6Al-4V?
11. What are the optimum conditions to achieve optimum perfonnances in this
research?