i

ABSTRACT

Electrical discharge machining (EDM) is a widespread process which works very

effectively in machining of micro holes and harder material with high dimension

accuracy. In this study, the objective is to optimize the machining parameter of the EDM

process including peck current, pulse duration, and with or without flushing process to

increase the material removal rate and reduce the electrode wear rate. EDM machine

model MITSUBISHI has been used in this project and the weight for the workpiece and

electrode has been measured using the digital weight machine. The material removal rate

and electrode wear rate were calculated using the formula. Copper has been used as

electrode to machine the tungsten carbide, which is widely used to make micro die for

plastic extrusion. Response surface methodology (RSM) method has been applied in this

project at two levels (high, +1 and low, -1) and there are 26 experiments have been done.

From the result, the lowest material removal rate is 4.55952E-006g/second while the

maximum material removal rate is 5.49336E-005g/second. The lowest electrode wear

rate is 1.91171E-006g/second while maximum electrode wear is 6.30569-005g/second.

The optimum machining parameter to increase material remove rate and reduce the

electrode wear rate are 14.67 A of peak current, 2.57 μs pulse on time and ON the

flushing process.

ii

ABSTRAK

Electrical discharge machining (EDM) ialah proses yang digunakan untuk menjalankan

pemotongan lubang yang bersaiz mikro dan bahan yang keras dengan ukuran yang tepat.

Dalam projek ini, pembolehubah yang dikawal ialah peak current, pulse duration, dan

sistem flushing. Hasil yang telah diuji ialah kadar pemotongan bahan kerja dan kadar

kehausan bagi electrode. Mesin EDM model MITSUBISHI digunakan untuk memotong

benda kerja tungsten carbide dengan menggunakan electrode kuprum. Berat electrode

dan bahan kerja diukur dengan menggunakan mesin penimbang digital sebelum dan

selepas ujukaji. Masa untuk pemotongan bahan kerja dicatatkan dan kadar pemotongan

bahan kerja dan kadar kehausan electrod dikira dengan formula. Jumlah eksperimen

yang telah dijalankan ialah 26 kali dan response surface methodology (RSM) digunakan

dalam projek ini untuk menentukan pembolehubah yang paling sesuai untuk mencapai

kadar pemotongan bahan kerja yang maximum dan kadar kehausan electrod yang

minimum. Nilai untuk kadar pemotongan bahan kerja maksimum dalam projek ini ialah

5.49336E-005g/saat sementara minimum adalah 4.55952E-006g/saat. Nilai maksimum

untuk kadar kehausan electrod ialah 6.30569-005g/saat sementara minimum ialah

1.91171E-006g/saat. Pembolehubah yang paling sesuai untuk mencapai kadar

pemotongan bahan kerja yang maksimum dan kadar kehausan electrod yang minimum

ialah 14.67 A of peak current, 2.57 μs pulse on time dan flushing system ON.

iii

DEDICATION

This project is dedicated to my parent, without whose caring support it been possible to

done the project. Besides that, this project also dedicated to sister and brother, who

support me in knowledge and other.

iv

ACKNOWLEDGEMENT

I am heartily thankful to my supervisor, Miss Liew Pay Jun, whose encouragement,

guidance and support from the initial to the final level enabled me to develop an

understanding of the project. Lastly, I offer my regards and blessings to all of those who

supported me in any respect during the completion of the project. Besides that, I want to

thank my parent that always supports me in project.

v

TABLE OF CONTENT

Abstract i

Abstrak ii

Dedication iii

Acknowledgement iv

Table of Content v-vii

List of Table viii-ix

List of Figure x-xi

List Abbreviations xii

1. INTRODUCTION 1

1.1 Introduction 1-2

1.2 Problem Statement 3

1.3 Objective 3

1.4 Scope 3-4

1.5 Important of Study 4

1.6 Expected Result 4

2. LITERATURE REVIEW 5

2.1 Principle of EDM 5-6

2.2 The Electrode 7-8

2.2.1 Copper Electrode 9

2.3 Tungsten Carbide 10

2.4 Dielectric Fluid 10-11

2.5 EDM Parameter 11

2.5.1 Flushing 11-12

2.5.2 Peak Current, IP 12

2.5.3 Pulse-on Time, On 12-13

2.5.4 Pulse-off Time, OFF 13

vi

2.6 EDM Machining Characteristics 13

2.6.1 Electrode Wear Rate 13-14

2.6.2 Material Removal Rate 14

2.7 Design of Experiment (DOE) 14-15

2.7.1 Response Surface Methodology (RSM) 15-17

2.8 Summary Previous Journal 18-22

2.9 Summary 23

3. METHODOLOGY 24

3.1 Flow Chart of Study 25

3.2 Step 1: Define the Objective for the Project 26

3.3 Step 2: Identify the Machining Parameter and Response Variable 26

3.3.1 Variable Machining Parameter 26

3.3.2 Constant Machining Parameter 27

3.4 Step 3: Preparation of the Experiment 27

3.4.1 Workpiece 27-28

3.4.2 EDM Electrode 28-29

3.4.3 Digital Weight Machine 29

3.4.4 Design of Experiment Matrix 30

3.5 Step 4: Running the Experiments 31

3.5.1 Machining Flow Chart 32

3.5.2 Testing the Finish Produce 33

3.6 Step 5: Analysis Result 33

3.6.1 Material Removal Rate (MRR) Measurement 34

3.6.2 Electrode Wear Rate (EWR) Measurement 34

3.7 Step 6: Define the Optimal Setting of Experimental Parameters 35

3.8 Step 7: Confirmation Run 35

3.9 Step 8: Make Conclusion for Project 35

4. RESULTS AND DISCUSSION 36

4.1 Result 36-37

vii

4.2 Analysis of Material Removal Rate 37-38

4.2.1 Fit Summary 38-39

4.2.1.1 Lack of Fit 39

4.2.1.2 Model Summary Statistic 40-41

4.2.2 ANOVA 41-43

4.2.3 Model Graphs 43-47

4.3 Analysis of Electrode Wear Rate 48

4.3.1 Fit Summary 48-49

4.3.1.1 Lack of Fit 49

4.3.1.2 Model Summary Statistic 49-51

4.3.2 ANOVA 51-52

4.3.3 Model Graphs 53-57

4.4 Optimization 57

4.4.1 Numerical 57-58

4.5 Confirmation Run 59

4.5.1 Average Deviation Percentage Value 59

4.5.1.1 Material Removal Rate 60

4.5.1.2 Electrode Wear Rate 60-61

4.6 Discussion 61

4.6.1 Material Removal rate 61-62

4.6.2 Electrode Wear Rate 62-63

5. CONCLUSION AND RECOMMENDATIONS 64

5.1 Conclusion 64

5.2 Recommendation 65

REFERENCES 66-67

APPENDICES

A Gantt chart PSM 1

B Gantt chart PSM 2

1

CHAPTER 1

INTRODUCTION

This chapter is introduces the micro EDM process and problem statement. Besides that,

this chapter also includes the objective, scope, importance of study and expected result

for the project.

1.1 Introduction

Rapid advances in technology require further development in the manufacturing of

micro parts and micro-electromechanical system components. Increasing demand for

micro-parts made micro-machining processes more focused and investigated among the

front end of the technology in recent years. Micro-machining is the basic manufacturing

technology of the miniaturized and smaller parts having size of millimeter down to

micrometer.

Electrical Discharge Machining (EDM) is one of the machining processes that may have

high potential to manufacture small size components. It is a thermal process that utilizes

spark discharges to erode a conductive material and electrode is almost unloaded. There

is no physical contact between the tool electrode and the work piece so the process

works efficiently and particularly in the machining of hardness material. When the same

process principles are applied to the micro machining, the process is called as micro-

EDM.

2

The basic physical characteristics of the micro EDM process is essentially similar to that

of the conventional EDM process but the main difference is the size of the electrode that

used. Electrical discharge machining is widely used in machining of dies and for

produce of unusually shaped or size production work. Example for EDM products are

fuel injector valves, parts and components for medical devices, fiber optic connectors,

micro mold making, stamping tools and micro electronic parts.

There are many manufacturing techniques to drill micro holes and micro parts beside

micro-EDM. The recently developed methods are Wire Electric Discharge Grinding

(WEDG), Micro-Electrochemical Machining (MECM), Laser-Beam Machining (LBM),

Focused Ion Machining (FIM), Micro milling, Micro Ultrasonic Machining (MUSM),

Electrochemical Discharge Machining (ECDM) and Micro punching. Performances of

these methods are unique, because they have different machining mechanisms. For

example, LBM can be used to drill a hole under diameter of 4 μm, however, it causes

deterioration and micro cracks on the machined surface. Besides that, ECDM can

improve the material removal rate to 1.5 mm/min and surface roughness to 0.08 μm.

However, the walls of the micro-holes are over etched (Yan et al, 2002).

Micro EDM is suitable for these and similar applications because its low discharges

energy generate smooth surfaces and that have no physical contact between the tool

electrode and the work piece so the process works efficiently. However, micro EDM

face two significant challenges that is high electrode wear and low Material Removal

Rate (MRR). Electrode wear which results from each discharge removing some material

from the electrode, degrades the geometric accuracy of machined features.

This report was analysis the MRR and EWR for the process by using the different

machining parameter that are peak current, pulse on time and add the flushing process

when machining. The type of electrode is copper and the material is tungsten carbide. At

the end, this project were also determined the optimum machining parameter to get the

good result.

3

1.2 Problem Statement

In micro EDM process, the pulse on time, peak current and flushing are very important

machining parameter because it can control material remove rate and electrode wear rate.

However, there are difficulties to determine the optimum machining parameter to

increase the material remove rate and reduce the electrode wear rate. The unsuitable

pulse duration and peak current will increase the cost of production. Besides that, adding

the dielectric fluid flushing process will increase the material remove rate.

In this study, that were determined the optimum machining parameter to increase

material remove rate and reduce the electrode wear rate.

1.3 Objective

The objectives of this experiment are to:

1. Analysis the material remove rate and electrode wear rate for the process by

using the different machining parameter sure as peak current, pulse on time and

the flushing process.

2. Determine the optimum machining parameter to increase material remove rate

and reduce the electrode wear rate.

1.4 Scope

This project were analysis the material remove rate and electrode wear rate relate to the

EDM machining parameter such as peak current, pulse on time and the adding the

flushing process when machining. The type of electrode is copper and the material is

tungsten carbide. This study were not included the surface roughness for the work piece

and the other EDM machining parameter. Response surface methodology has been

applied in this project.

4

1.5 Important of Study

This project were defined the suitable EDM machining parameter such as peak current,

pulse on time and the flushing process to get more material remove rate and less of the

electrode wear rate. Besides that, this study was bringing benefit for industry to

minimize the costs when using the EDM machining to process the tungsten carbide.

1.6 Expected Result

At the end of this project, we were determined the optimum machining parameter to

increase material remove rate and reduce the electrode wear rate.

5

CHAPTER 2

LITERATURE REVIEW

This chapter discuss about the principle of EDM, electrode, material (tungsten carbide),

dielectric fluid, flushing process, machining parameter, and EDM machining

characteristics. Besides that, summary of the previous journal is included at the end of

this chapter.

2.1 Principle of EDM

Electrical discharge machine is a controlled metal remove technique whereby an electric

spark is used to cut (erode) the work piece, which takes a shape opposite to that of the

cutting tool or electrode. The electrode is made from electrically conductive material,

usually carbon. The die sinking electrode, made to the shape of the cavity required, and

the work piece are both submerged in dielectric fluid light lubricating oil). This

dielectric fluid should be a nonconductor (or poor conductor) of electricity. A servo

mechanism maintains a gap of about 0.0005 to 0.01 in. (0.01 to 0.02mm) between the

electrode and the work, preventing them from coming into contact with each other. A

direct current of low voltage and high amperage is delivered to the electrode at the rate

of approximately 20000 hertz (Hz). These electrical energy impulses vaporize the oil at

this point. This permits the spark to jump the gap between the electrode and the work

piece through the dielectric fluid. Intense heat is created in the localized area of the

spark impact; the metal is expelled from the surface of the work piece. The dielectric

fluid, which is constantly being circulated carries away the eroded particles of metal

6

during the off-cycle of the pulse and assists in dissipating the heat caused by the spark.

(Steve et al, 2005)

Figure 2.1: a) A controlled spark remove metal during electrical discharge machining (EDM); b) basic

element of an electrical discharge system.

Figure 2.2: Stages of single spark

Electrode

Servo

Work piece

Material

Electrode

7

2.2 The Electrode

The electrode in die sinking EDM is formed to the shape of the cavity desired. As in

conventional machining, some materials have better cutting and wearing qualities than

others. Therefore, electrode must have the following characteristics:

Be good conductors of electricity and heat.

Be easily machined to shape at a reasonable cost

Produce efficient metal removal from the work piece

Resist deformation during the erosion process

Exhibit low electrode (tool) wear rates

The most common electrode materials are graphite, copper, copper graphite, copper

tungsten, brass, and steel. None of these electrode materials has general-purpose

application. Each machining operation dictates the selection of the electrode material.

Copper produces better results in the resistance capacitance circuits where higher

voltages are employed. It is commercially available in various shapes and side, is

relatively inexpensive, can be machined easily, and makes an excellent electrode. Its tool

wear rate is much less and its high metal removal ate is almost double that of nay other

electrode material (Steve et al, 2005).

8

Table 2.1: Selection of electrode material (Pandey et al, 2008)

Material Wear ratio Metal

removal rate

Fabrication Cost Application

Copper Low High on

rough range

Easy can be

sprayed also

High On all metals

Brass High High only on

finishing

ranges

Easy Low On all metals

Tungsten Lowest Low Difficult High Only where

small holes are

to be drilled

Tungsten

copper

alloys

Low Low Difficult High Used for higher

accuracy work

Cast iron Low Low Easy Low Can be used

only on few

material

Steel High Low Easy Low Can be used for

finishing only

Zinc based

alloys

High High on

rough range

Easily die cast Low Can be used in

all metals

Copper

graphite

Low High Very delicate

and hence

difficult

High Can be used on

all metals