Study Of Sharp Edge Cutting In Wire EDM.
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 (√)
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JLN. IKAN AYU, CHERAS,
56000, KUALA LUMPUR
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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
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………………………………………………………….
Author’ s Name
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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 120o 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.
i
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 30 o dan 120o
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.
ii
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.
iii
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.
iv
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
v
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
vi
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
57
Influence of wire tension
4.4.2.1 Influence of wire tension with different peak current at angle 30
o
4.4.2.2 Influence of wire tension with different peak current at angle 120o
57
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
5.4
roughness at angle 30o and 120o
64
Effect of peak current and wire speed on dimensional accuracy
65
5.4.1 Comparison of peak current and wire speed effect on dimensional
5.5
accuracy at angle 30o and 120o
66
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
5.6
error at angle 30o and 120o
68
Effect of peak current and wire tension on surface roughness
69
5.6.1 Comparison of peak current and wire tension effect on surface
5.7
roughness at angle 30o and 120o
70
Effect of peak current and wire tension on dimensional accuracy
71
5.7.1 Comparison of peak current and wire tension effect on dimensional
5.8
accuracy at angle 30o and 120o
72
Effect of peak current and wire tension on sharp edge error
73
vii
5.8.1 Comparison of peak current and wire tension effect on sharp edge
error at angle 30o and 120o
74
6.
DISCUSSION AND RECOMMENDATIONS
6.1
Conclusion
75
6.2
Recommendations
77
REFERENCES
78
viii
LIST OF TABLES
2.1
ISO standard Ra value for common manufacturing method
3.1
Constant parameters for machining mild steel workpiece material
using brass wire at diameter 0.25 mm
3.2
33
39
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
ix
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
x
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
5.2
63
Effects of wire speed and peak current on surface roughness of
workpiece at angle 120o
5.3
63
Effects of wire speed and peak current on dimensional accuracy of
workpiece at angle 30o
5.4
65
Effects of wire speed and peak current on dimensional accuracy of
workpiece at angle 120o
5.5
65
Effects of wire speed and peak current on sharp edge error of
workpiece at angle 30o
5.6
67
Effects of wire speed and peak current on sharp edge error of
workpiece at angle 120o
5.7
67
Effects of wire tension and peak current on surface roughness of
workpiece at angle 30o
5.8
69
Effects of wire tension and peak current on surface roughness of
workpiece at angle 120o
5.9
69
Effects of wire tension and peak current on dimensional accuracy of
workpiece at angle 30o
5.10
71
Effects of wire tension and peak current on dimensional accuracy of
workpiece at angle 120o
5.11
71
Effects of wire tension and peak current on sharp edge error of
workpiece at angle 30o
5.12
73
Effects of wire tension and peak current on sharp edge error of
workpiece at angle 120o
73
xi
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
xii
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
1
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 nonconventional 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
2
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
3
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 120o.
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
4
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.
5
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:
6
(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.
7
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.
8
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
√
(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)
TIDAK TERHAD
Disahkan oleh:
(TANDATANGAN PENULIS)
Alamat Tetap:
54-03-06 FLAT SRI SABAH,
JLN. IKAN AYU, CHERAS,
56000, KUALA LUMPUR
Tarikh: _______________________
(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
:
………………………………………………………….
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 120o 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.
i
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 30 o dan 120o
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.
ii
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.
iii
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.
iv
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
v
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
vi
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
57
Influence of wire tension
4.4.2.1 Influence of wire tension with different peak current at angle 30
o
4.4.2.2 Influence of wire tension with different peak current at angle 120o
57
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
5.4
roughness at angle 30o and 120o
64
Effect of peak current and wire speed on dimensional accuracy
65
5.4.1 Comparison of peak current and wire speed effect on dimensional
5.5
accuracy at angle 30o and 120o
66
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
5.6
error at angle 30o and 120o
68
Effect of peak current and wire tension on surface roughness
69
5.6.1 Comparison of peak current and wire tension effect on surface
5.7
roughness at angle 30o and 120o
70
Effect of peak current and wire tension on dimensional accuracy
71
5.7.1 Comparison of peak current and wire tension effect on dimensional
5.8
accuracy at angle 30o and 120o
72
Effect of peak current and wire tension on sharp edge error
73
vii
5.8.1 Comparison of peak current and wire tension effect on sharp edge
error at angle 30o and 120o
74
6.
DISCUSSION AND RECOMMENDATIONS
6.1
Conclusion
75
6.2
Recommendations
77
REFERENCES
78
viii
LIST OF TABLES
2.1
ISO standard Ra value for common manufacturing method
3.1
Constant parameters for machining mild steel workpiece material
using brass wire at diameter 0.25 mm
3.2
33
39
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
ix
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
x
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
5.2
63
Effects of wire speed and peak current on surface roughness of
workpiece at angle 120o
5.3
63
Effects of wire speed and peak current on dimensional accuracy of
workpiece at angle 30o
5.4
65
Effects of wire speed and peak current on dimensional accuracy of
workpiece at angle 120o
5.5
65
Effects of wire speed and peak current on sharp edge error of
workpiece at angle 30o
5.6
67
Effects of wire speed and peak current on sharp edge error of
workpiece at angle 120o
5.7
67
Effects of wire tension and peak current on surface roughness of
workpiece at angle 30o
5.8
69
Effects of wire tension and peak current on surface roughness of
workpiece at angle 120o
5.9
69
Effects of wire tension and peak current on dimensional accuracy of
workpiece at angle 30o
5.10
71
Effects of wire tension and peak current on dimensional accuracy of
workpiece at angle 120o
5.11
71
Effects of wire tension and peak current on sharp edge error of
workpiece at angle 30o
5.12
73
Effects of wire tension and peak current on sharp edge error of
workpiece at angle 120o
73
xi
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
xii
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
1
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 nonconventional 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
2
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
3
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 120o.
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
4
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.
5
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:
6
(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.
7
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.
8