universiti teknikal malaysia melaka study of sharp edge...

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

Study of Sharp Edge Cutting In Wire EDM

This report submitted in accordance with requirement of the Universiti Teknikal Malaysia

Melaka (UTEM) for the Bachelor Degree of Manufacturing Engineering (Manufacturing

Design) with Honours

by

Nur Zahirah binti Zakria @ Zakaria

FACULTY OF MANUFACTURING ENGINEERING

2009

UTeM Library (Pind.1/2007)

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA

TAJUK: Study of Sharp Edge Cutting in Wire EDM

SESI PENGAJIAN: 2008/2009 Semester 2

Saya: NUR ZAHIRAH BINTI ZAKRIA @ ZAKARIA

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 punulis . 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja. 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 yang termaktub di dalam

AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan

oleh organisasi/badan di mana penyelidikan dijalankan)

(TANDATANGAN PENULIS)

Alamat Tetap: 54-03-06 FLAT SRI SABAH, JLN. IKAN AYU, CHERAS, 56000, KUALA LUMPUR Tarikh: _______________________

Disahkan oleh:

(TANDATANGAN PENYELIA)

Cop Rasmi: Tarikh: _______________________

** Jika laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai

SULIT atau TERHAD.

DECLARATION

I hereby, declared this thesis entitled “Study of Sharp Edge Cutting in Wire EDM” is

the result of my own research except as cited in references.

Signature : ………………………………………………………….

Author’ s Name : ………………………………………………………….

Date : ………………………………………………………….

i

ABSTRACT

Wire electrical discharge machining (WEDM) is a thermal machining process by the

usage of an electrode to begin the sparking process. During the WEDM process, the

material is eroded ahead of the wire and there is no direct contact between the

workpiece and the wire which could eliminate the mechanical stresses during

machining. The utilizing of continuous traveling wire electrode enables this machine

to machining parts with varying hardness or complex shapes accurately. However,

due to varying factors like wire tension, wire speed, angle of cut, open-circuit

voltage, current, dielectric flow and so on, WEDM could not achieve the accurate

dimension during machining especially when cutting the sharp edge at a particular

angle. Thus, this study is conducted to finds out the best optimum conditions using

WEDM machine (Mitsubishi RA90) in Universiti Teknikal Malaysia Melaka

(UTeM) to fabricate high quality products in terms of surface roughness, sharp edge

angle and dimensional accuracy. A triangle shape that contains 30o and 120

o angle is

cut on a mild steel plate to analyze the performance parameters characteristics under

different machining conditions or design parameters that have been selected. All the

performance parameters are tested using suitable measurement equipment. The

surface roughness tester is equipment used to measure the texture of the sample

surface. The dimensional accuracy will be measured using optical comparator and

meanwhile the accuracy of sharp edge error is analyzed using digital imaging and

measurement system. Then, all the data are collected in tables and graphs form to

ease the process of data interpretation.

ii

ABSTRAK

WEDM atau Mesin Dicas Elektrik Wayar ialah suatu proses pemesinan termal

dengan penggunaan elektrod bagi mencetuskan proses percikan. Semasa proses

WEDM, bahan kerja dihakis ke hadapan oleh wayar dan tanpa sebarang hubungan

terus secara langsung antara bahan kerja dengan wayar yang mana dapat

menghapuskan tekanan mekanikal semasa proses pemesinan. Penggunaan wayar

elektrod yang sentiasa bergerak secara berterusan membolehkan mesin ini untuk

memesin komponen yang mempunyai pelbagai jenis kekerasan atau bentuk

kompleks dengan tepat. Walau bagaimanapun, disebabkan pelbagai faktor seperti

ketegangan wayar, kelajuan wayar, sudut pemotongan, voltage litar terbuka, arus

elektrik, arus dielektrik dan lain-lain lagi, menyebabkan WEDM tidak dapat

menghasilkan dimensi yang tepat semasa proses pemesenan terutama skali ketika

memotong sisi tajam pada suatu sudut. Oleh itu, kajian ini dijalankan untuk

mengenalpasti keadaan optimum yang paling baik menggunakan mesin WEDM

(Mitsubishi RA90) yang disediakan di makmal FKP, UTeM untuk menghasilkan

produk yang berkualiti tinggi dari segi kelicinan permukaan, sisi suatu sudut tajam

dan ketepatan dimensi. Satu bentuk segitiga yang mempunyai sudut 30o dan 120

o

dipotong pada satu kepingan milsteel untuk menganalisa ciri-ciri parameter yang

terhasil dalam pelbagai keadaan pemesenan atau parameter rekaan yang telah dipilih.

Penguji kekasaran permukaan adalah alat yang digunakan untuk mengukur tekstur

permukaan sampel. Ketepatan dimensi akan diukur menggunakan pembanding optik

manakala ketepatan sudut sisi tajam dianalisa menggunakan mikroskop alat.

Kemudian, semua data dikumpulkan dalam bentuk jadual dan graf untuk

memudahkan proses tafsiran data dibuat.

iii

DEDICATION

For my beloved father, Zakaria bin Idrus and my mother, Halimah binti

Sulaiman, sis and bro thank you for your encouragement and

understanding during completing this project.

Also dedicated to all my friends who always support and giving hands to

help me without hoping any rewards. Your effort in helping me cannot be

repaid with any valuable things.

Not forgetting my supervisors, En. Abd. Halim Hakim b. Abd. Aziz.

Without his commitment, guide and advice it is impossible for me to

complete this project.

iv

ACKNOWLEDGEMENT

First and foremost, a very thankful to Allah for his Mercy, the author could

finally finish this project prosperously, after experience a lot of obstacles and

challenges. An appreciation goes to the author’s PSM supervisor, Encik Abd. Halim

Hakim b. Abd. Aziz for his untiring devotion in reading, checking and guiding in this

project. At the same time, the author wish to express her sincere thanks towards her

parents and siblings for enthusiastic support in finance, moral, guidance and all their

contributions in order to finish this industrial training successfully. Not forgetting her

beloved friends for always helping her in develop the ideas and explain whatever

things that the author couldn’t understand. Thanks to Universiti Teknikal Malaysia

Melaka for providing the equipments and materials needed for the students to

execute their researches especially for PSM project which is compulsory done by

undergraduate students at final year to complete their studies. From this precious

moment, a lot of new things could be gained by the students besides getting more

understand about the concept that need to be used in any of their project studies.

They also capable to apply the knowledge that they have learned to finish their

project. The trainee’s gratitude also goes to those who had spent their time to teach,

explain and answer all the questions. Last but not least, the author would like to

address her thanks for those who have contributed directly or indirectly during the

making of this project.

v

TABLE OF CONTENT

Abstract i

Abstrak ii

Dedication iii

Acknowledgement iv

Table of Contents v

List of table ix

List of figure x

List of Abbreviations xii

1. INTRODUCTION

1.1 Background 1

1.2 Problem statements 3

1.3 Objectives of study 3

1.4 Scope of the limitation 4

1.5 Importance of study 4

1.6 Outline of study 4

2. LITERATURE REVIEW

2.1 Electrical Energy Processes 6

2.2 Introduction of EDM 9

2.2.1 History of EDM 10

2.2.2 Application of EDM 10

2.2.3 Principles of EDM 11

2.2.4 Circuits of EDM 12

2.2.5 Advantages and limitations of EDM 15

2.3 Introduction of wire EDM (WEDM) 16

2.3.1 History of wire EDM 16

2.3.2 Wire cut EDM machine 17

2.3.3 Process of wire EDM 18

2.3.4 Operating system of wire EDM 19

2.3.4.1 Servo mechanism 19

vi

2.3.4.2 Dielectric fluid 20

2.3.4.3 Electrode 20

2.3.4.4 Machine control unit 21

2.4 Sharp edge cutting 22

2.5 Factors affecting geometrical accuracy of sharp edge cutting 23

2.5.1 Cutting conditions 24

2.5.2 Cutting regime 25

2.5.3 Type of cut 25

2.5.4 Different properties of the workpiece material 26

2.5.5 Machine characteristics 26

2.5.6 Dielectric fluid 27

2.5.7 Component geometry 27

2.6 Performance parameter 28

2.6.1 Sharp edge angle 28

2.6.2 Dimensional Accuracy 29

2.6.3 Surface Integrity 29

2.6.3.1 Surface finish definition 30

3. METHODOLOGY

3.1 Process flow chart 34

3.1.1 Problem statements and objectives identification 35

3.1.2 Data or information gathering 35

3.1.3 Experiment preparation 35

3.1.4 Machine parameter setting 38

3.1.5 Measurement analysis on the product 39

3.1.6 Data obtained interpretation 39

3.2 Gantt chart 40

3.3 K-Chart 42

3.4 Wire Cut EDM (Mitsubishi RA 90 model) 43

3.5 Brass wire 44

3.6 Mildsteel 45

3.7 Measurement equipments 46

3.7.1 Digital Imaging and Measuring System Equipment 46

3.7.2 Optical Comparator 47

vii

3.7.3 Surface Finish Analysis 48

4. RESULTS

4.1 Surface roughness data measurement 50

4.2 Dimensional accuracy data measurement 52

4.3 Sharp edge accuracy data measurement 53

4.4 Experimental results 54

4.4.1 Influence of wire speed

4.4.1.1 Influence of wire speed with different peak current at angle 30o 54

4.4.1.2 Influence of wire speed with different peak current at angle 120o 55

4.4.2 Influence of wire tension 57

4.4.2.1 Influence of wire tension with different peak current at angle 30o 57

4.4.2.2 Influence of wire tension with different peak current at angle 120o 58

5. DISCUSSIONS

5.1 Data interpretation 60

5.2 Influence of wire speed, wire tension and peak current 60

5.3 Effect of peak current and wire speed on surface roughness 63

5.3.1 Comparison of peak current and wire speed effect on surface

roughness at angle 30o and 120

o 64

5.4 Effect of peak current and wire speed on dimensional accuracy 65

5.4.1 Comparison of peak current and wire speed effect on dimensional

accuracy at angle 30o and 120

o 66

5.5 Effect of peak current and wire speed on sharp edge error 67

5.5.1 Comparison of peak current and wire speed effect on sharp edge

error at angle 30o and 120

o 68

5.6 Effect of peak current and wire tension on surface roughness 69

5.6.1 Comparison of peak current and wire tension effect on surface

roughness at angle 30o and 120

o 70

5.7 Effect of peak current and wire tension on dimensional accuracy 71

5.7.1 Comparison of peak current and wire tension effect on dimensional

accuracy at angle 30o and 120

o 72

5.8 Effect of peak current and wire tension on sharp edge error 73

viii

5.8.1 Comparison of peak current and wire tension effect on sharp edge

error at angle 30o and 120

o 74

6. DISCUSSION AND RECOMMENDATIONS

6.1 Conclusion 75

6.2 Recommendations 77

REFERENCES 78

ix

LIST OF TABLES

2.1 ISO standard Ra value for common manufacturing method 33

3.1 Constant parameters for machining mild steel workpiece material

using brass wire at diameter 0.25 mm 39

3.2 Variable parameters for machining mild steel workpiece material

using brass wire at diameter 0.25 mm 39

3.3 Gantt chart for PSM 1 and 2

4.1 Influence of wire speed with different peak current at angle 30o 54

4.2 Influence of wire speed with different peak current at angle 120o 55

4.3 Influence of wire tension with different peak current at angle 30o 57

4.4 Influence of wire tension with different peak current at angle 120o 58

x

LIST OF FIGURES

2.1 Schematic of Electro-Discharge Machining (EDM) 7

2.2 Schematic of Electro-Chemical Machining (ECM) 7

2.3 Schematic of Ultrasonic Machining (USM) 8

2.4 Schematic of Magnetic Pulse Forming 8

2.5 Electrolytic Grinding (EG) 9

2.6 Various kind of products manufactured using EDM 10

2.7 Basic features of electrical-discharge machining 12

2.8(a) Relaxation-type power supply 14

2.8(b) Pulse-type power supply 14

2.9 Effects on cratering and surfaces finish using various frequencies

of spark discharge 14

2.10 Outline of wire EDM machine 17

2.11 Overview of wire EDM operates 19

2.12 Error in sharp edge cutting 22

2.13 Numerous type of taper machining using Wire EDM 26

2.14 Sketch map of sharp edge machining 29

2.15 Surface characteristics 30

3.1. Process flow chart

3.2. llustration of drawing of workpiece material in CAD/W software

3.3. Upper and lower nozzle is set to the suitable clearance 38

3.4. K-Chart (The blue box highlight the flow of the study) 42

3.5. Wire Cut EDM (Model Mitsubishi RA) 44

3.6. Varieties kind of brass wire 45

3.7. Various size of Mild steel plate 46

3.8. Digital Imaging and Measuring System Equipment 46

3.9. Optical Comparator 48

3.10. Surface roughness tester 49

4.1 Measuring of surface roughness of an edge using surface roughness

xi

tester 51

4.2 Surface roughness and dimensional accuracy measuring method 51

4.3 Probably error happen if using Coordinate Measuring Machine (CMM) 52

4.4 Specimen image appear on screen monitor 53

5.1 Effects of wire speed and peak current on surface roughness of

workpiece at angle 30o 63

5.2 Effects of wire speed and peak current on surface roughness of


5.3 Effects of wire speed and peak current on dimensional accuracy of

workpiece at angle 30o

65

5.4 Effects of wire speed and peak current on dimensional accuracy of


5.5 Effects of wire speed and peak current on sharp edge error of


5.6 Effects of wire speed and peak current on sharp edge error of


5.7 Effects of wire tension and peak current on surface roughness of


5.8 Effects of wire tension and peak current on surface roughness of

workpiece at angle 120o

69

5.9 Effects of wire tension and peak current on dimensional accuracy of


5.10 Effects of wire tension and peak current on dimensional accuracy of


5.11 Effects of wire tension and peak current on sharp edge error of


5.12 Effects of wire tension and peak current on sharp edge error of


xii

LIST OF ABBREVIATIONS

B.C. – Before century

CNC – Computer Numerated Circuit

ECM – Electro Chemeical Machining

EG – Electro grinding

EDM – Electric Discharge Machine

PSM – Projek Sarjana Muda

USM – Ultrasonic machining

WEDM – Wire Electro Discharge Machine

HAZ – Heat Affected Zone

MRR – Material Removal Rate

CMM – Coordinate Measuring Machine

1

CHAPTER 1

INTRODUCTION

“The word manufacturing is derived from the Latin manu factus, meaning made by

hand.” The word manufacture first appeared in 1567, and the word “manufacturing”

appeared in 1683. The word product means something that is produced, and the word

“product” and production first appeared sometime during the 15th century. The word

“manufacturing” and “production” often are used interchangeably. (Kalpakjian, S.

and Schmid, S., 2006)

1.1 Background

Material and manufacturing process has been developed gradually over the centuries

using new materials and complex operations. It started in 4000 B.C., using material

existed during that period such as stone, flint, wood, bone, ivory, and composite

tools. All these material are using the muscle power to be used. Then, basics

equipments like hoe, hammer and axe are invented. These inventions still need the

human energy to be generated. It also need to be improve since there are a lot of

limitations especially when manufacturing the harden material.

More energy required to enables the product to be manufactured. Due to that reason,

more complicated machines are created to replace human power and to make the

manufacturing of the product easier. This kind of machine is known as conventional

machines. This machine can be categorized as semi-auto machine because human

energy still needed to handle the machine. The product quality of this machine is

depends on the operator who is handling the machine. Problems still occurs when

2

using this machine. Since this machine also depending on human’s ability, the

quality of the product is not very satisfied. It is hard to achieve the accuracy required

since all the setting is done manually. In addition, there are a lot of new harden

material existed which cannot be machined by the conventional machine. Thus, it is

the need to create a machine that integrates with the computer to make the machining

operation more effective and efficient.

Utilization of computers in manufacturing applications has proved to be one of the

most significant developments over the last couple of decades in helping to improve

the productivity and efficiency of manufacturing systems. These advance methods,

which in the past have been called nontraditional or unconventional machining began

to be introduces in the 1940’s (Kalpakjian, S. and Schmid, S., 2006). These

requirements lead to the development of electrical-discharge machining, chemical,

electrical, laser and high-energy beams as energy sources for removing material from

metallic or non-metallic workpiece. Developments of nontraditional machining have

given a lot of benefits to industry applications. It has been commonly used in

automotive, aerospace, mould tool and die making industries.

Since this kind of machining approach has been using in a lot of critical sectors and

industries, the qualities of every product that will be manufactured need to be precise

and really high quality in meeting the demands. Due to this reason, one of non-

conventional machining which is electrical-discharge machining (EDM) is taken to

be studied in this research to perform a very good machining condition while

manufacturing every component. The electrical-discharge machining (EDM) can be

used for all electrically conducting materials regardless of its hardness. Geoffrey, B.

and Winston A.K., 1989 stated that the two most common EDM machines are wire

cut and the vertical ram type. This study wills only covers only on Wire EDM

(WEDM) type. WEDM is an adaptation of the basic EDM process, which can be

used for cutting complex 2-dimensional and 3-dimensional shapes through

electrically conducting materials. The workpiece is moved under computer numerical

control (CNC) relative to the wire and this enables complex shaped profiles to be cut

through sheet and plate materials. However, it seems hard to get the accurateness of

the manufacturing part since the accuracy of the parts machine is depending on the

shape of the geometry being machined. The problem of inaccuracy is obviously

3

happen when sharp edge machining is executed. The edge or corner of the

component that should be sharp at a particular angle desired, tend to form a radius

shape. Thus, this study is conducted to find the best optimum condition in order to

increase the accuracy of the product.

1.2 Problem statement

Electrical Discharge Machining (EDM) has become an economic, rapid and highly

efficient process for machining all conductive materials. It is capable of machining

various shapes of parts precisely. However, the problem comes when the sharp edge

of the angle does not perform at the accurate angle that has been desired after

machining process. It tends to build a fillet at the angle. This problem could be very

critical when the product needed to be very precise especially when it needs to be

assembling with another part. It could give a very bad impact to the industry when it

is produced in a very big volume. Thus, this problem needs to be fixed so that the

product produced can be obtained under the quality control and easier the part to be

assembled with another part.

1.3 Objectives of study

The objectives of this study are:

(a) To study the cutting process of sharp edge

(b) To study the relationship of sharp edge error, surface roughness and

dimensional accuracy between two different angle

(c) To propose the optimum condition for machining sharp edge

4

1.4 Scope and limitation

Wire EDM machine, Mitsubishi RA 90 model will be used as the main machine to perform all

the results in this report. Any other types of wire EDM machine are not applicable since

different machine capability and errors for every different machine that will affect the findings

of this study. This machine is located at CNC laboratory in UTeM. Only brass wire at 0.25mm

in diameter will be used as the electrode of wire EDM machine (Mitsubishi RA 90 model). The

material will be used as the workpiece is mild steel at 10mm in thickness. This research is will

study the effects of peak current, wire tension and wire speed at angle 30o and 120

o.

1.5 Importance of study

The importances of this study are as follows:

(a) To enhance the machining ability in order to produce sharp edge at approximate angle using

wire EDM machine (Model Mitsubishi RA 90).

(b) To discover the best approach and optimum condition to produce better results in

terms of surface finish, sharp edge angle and dimensional accuracy using wire

EDM machine (Model Mitsubishi RA 90).

(c) To diminish scrap due to failure of the workpiece to achieve the desired

dimensional accuracy during the machining process

1.6 Outline of study

This report in total is about a study on the machining parameter needed to execute

the best quality for a sharp edge at certain angle. Basically, this report is divided into

5 chapters which lead to different contents in each chapter. Chapter 1 give an account

of narrate introduction and brief circumstances on the study that will be conducted. It

is consist of background, problem statement, objective of study, scope and limitation,

important of study and study outline. Next, chapter 2 is mainly about the literature

review which will covers the definition of the term and converse about wire EDM

5

machine and other machines that will be used to carried out the results. This chapter also

will intent explain on the functions, characteristics and operation of the machine used.

On chapter 3, the outline on methodology of this study will be described where the

operation method, types of material and optimum conditions are the main elements that

will be determined in this chapter. Then, chapter 4 will affix all the findings gathered

all the data into the tables while chapter 5 analyzed on the results obtained via graphs.

Last but not least is chapter 6 will conclude all the observations and findings. This

chapter also consists of recommendation as the suggestion to improve dimensional

accuracy of the corner using wire EDM machine.

6

CHAPTER 2

LITERATURE REVIEW

In this literature review, the author will discusses published information in this study

and evaluate the sources find by the author related to the study that the author wants

to focus. In this chapter, all information of the Discharge Machining, EDM

especially wire EDM machine is covered to give the ideas to the readers on what

wire EDM is all about. The authors also gathers all the facts that related to this study

to explain to the readers why this study is carried out and the briefly clarify the scope

of this studies so that the readers can get the concept of this entire study.

2.1 Electrical Energy Processes

Evolution of the technology nowadays makes it possible to the enlargement of new

harder metals but which cannot be economically machined by conventional methods.

Besides that, more complex shape and very small tolerance demanded have led to

difficulties in conventionally fabricating and machining varieties of shapes. Due to

this reason, the author finds that it is a need to find a process that could produce a

product more effectively with lower cost. The developments high heat resistant

alloys as the tool material for machining is widely and frequently used in industrial

field could cause a large capital investment to be produced. Thus, a new concept

needs to be used to reduce the manufacturing cost of a product and improve the tool

making techniques. These new needs have resulted in introduction of several new

electrical machining concepts. Lascoe O. D., 1973 classified the electrical machining

concepts into five main categories which are:

7

(a) Electro-Discharge Machining (EDM) (Figure: 2.1); which removing the

metal through the action of an electrical discharge of very short duration

and high current density between electrode and the work.

Figure 2.1: Schematic of Electro-Discharge Machining (EDM) (Lascoe O. D.,1973)

(b) Electro-Chemical Machining (ECM) (Figure: 2.2); which is an

electrolysis process where electro-chemical reaction dissolves metal from

a workpiece into an electrolyte solution.

Figure 2.2: Schematic of Electro-Chemical Machining (ECM) (Lascoe O. D.,1973)

(c) Ultrasonic Machining (USM) (Figure: 2.3); which use high frequency

mechanical vibration transmitted through a shaped tool to an abrasive grit

to remove material.

8

Figure 2.3: Schematic of Ultrasonic Machining (USM) (Lascoe O. D.,1973)

(d) Magnetic Pulse Forming (Figure: 2.4); which operates with precisely

controlled electro-magnetic forces. The interaction of the magnetic field

and the eddy current will create a uniform central force.

Figure 2.4: Schematic of Magnetic Pulse Forming (Lascoe O. D.,1973)

(e) Electrolytic Grinding (EG) (Figure: 2.5); which is a reverse or depleting

method of grinding employing metal-bonded diamond wheels and

electrolytic coolant supply.

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