Influence of electrical parameters and optimization of EDM performance measures on Ti 6A1 4V using DOE/TAGUCHI method

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"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"

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Signature

Supervisor

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

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

Ulltuk isteri

dall allak-allak

yallg mellceriakall sllasalla,

mak dall abalz serta keillarga yang memberi sokollgall

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

\.

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

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

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

2

1.2

3

1.3

1.4

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

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

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

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

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

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

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

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

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}

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

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

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.

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

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