MODELING PULSE POWER GENERATOR OF ELECTRICAL DISCHARGE
MACHINING
ADIBAH BINTI AHMAD
UNIVERSITI TEKNOLOGI MALAYSIA
MODELING PULSE POWER GENERATOR OF ELECTRICAL DISCHARGE
MACHINING
ADIBAH BINTI AHMAD
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Electronics and Telecommunication)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
JANUARY 2018
iii
Dedicated to my beloved mum
Zainab binti Abdullah
Beloved siblings
Azraimee bin Ahmad
Azren bin Ahmad
Azlinda binti Ahmed
Mohd Farid bin Ahmad
Azura binti Ahmad@Ahmed
Azimah binti Ahmed
Abdul Azim bin Ahmad@Ahmed
and
All my friends in MKEL programme
for their support and encouragement
iv
ACKNOWLEDGMENT
First and foremost, I am very grateful to ALLAH S.W.T. for giving me life and
chance to finish this project without much difficulty. Special thank goes to my helpful
supervisor Assoc. Prof. Dr. Azli bin Yahya. The supervision and support that he gave
truly helps the progression and smoothness of completing this project. The cooperation
is much indeed appreciated.
My grateful thanks go to my family for their endless support and
encouragement. My deepest gratitude also extends to all lecturers of Universiti
Teknologi Malaysia (UTM), for their guidance, ideas, and support in completing this
master project. This project had opened my eyes on solving real problems and I was
able to relate them with what I’ve been studied in UTM during the past 2 and half
years.
A number of individuals in Electrical and Biomedical faculty were very helpful
and understanding. I would like to acknowledge in particular for their contribution in
this work.
Last but not least, I would like to thank to all my friends especially Nur Akmal,
Mohd Azli, Rohana, Nor Dayana, Mohd Nur Amin, Chan Suei Ngan and Nazriah for
the wise idea and tips throughout the project works. I’m very much enjoy working
with all of you and thank you very much for all of the contributions and care.
v
ABSTRACT
Electrical Discharge Machining (EDM) is non-conventional manufacturing
process that uses electrical energy to shape the material, high voltage as the source
for removal, electrons as the medium to transfer the energy and spark erosion as
the mechanism that involves in the manufacturing process. A series of stochastic
sparks are produced when the gap between electrode and workpiece is very narrow
just about 10 to 50 microns. EDM has been introduced to this project due to the
capability covering a various type of conducting material such as steel, titanium,
super alloys, refractories and aluminum. The selection of EDM pulse power
generator is one of the most critical aspects to take into consideration in the
manufacturing process. This project focused on the modeling and analysis of pulse
power generator of EDM. A model of pulse power generator has been developed
by using model-based design tools MATLAB/Simulink. Pulse power generator
consists of power supply unit and pulse generator unit. The first section of pulse
power generator which is linear power supply has been modeled accordingly.
Similarly, the second section of pulse power generator which is the pulse generator,
the system has been modeled in order to analyse the pulse profile of EDM. The
characteristic of the pulse profile are an open circuit, normal discharge, arc and
short circuit condition during the machining process. A model of pulse power
generator has been presented and implemented successfully. The phases of the
pulses have been discussed thoroughly which are initial phase, ignition phase,
discharge phase and ejection phase. The pulse power generator model has been
simulated and validated by the experimental results of previous research.
vi
ABSTRAK
Electrical Discharge Machining (EDM) adalah proses pembuatan bukan
konvensional yang menggunakan tenaga elektrik untuk membentuk bahan,
menggunakan voltan tinggi sebagai sumber untuk penyingkiran, elektron sebagai
medium untuk memindahkan tenaga dan percikan hakisan sebagai kaedah dalam
proses pembuatan. Serangkaian bunga api stokastik dihasilkan apabila jurang antara
elektrod dan sekeping kerja sangat sempit hanya kira-kira 10 hingga 50 mikron. EDM
telah diperkenalkan dalam projek ini kerana keupayaan meliputi pelbagai jenis bahan
yang dijalankan seperti keluli, titanium, aloi super, refraktori dan aluminium.
Pemilihan penjana kuasa nadi EDM adalah salah satu aspek yang paling kritikal untuk
diambil kira dalam proses pembuatan. Projek ini memberi tumpuan kepada pemodelan
dan analisis penjana kuasa nadi EDM. Model penjana kuasa nadi telah dibangunkan
dengan menggunakan alat reka bentuk berasaskan model MATLAB / Simulink.
Penjana kuasa nadi terdiri daripada unit bekalan kuasa dan unit penjana nadi. Bahagian
pertama penjana kuasa nadi yang merupakan bekalan kuasa linear telah dimodelkan
dengan sewajarnya. Bahagian kedua penjana kuasa nadi yang merupakan penjana
denyut telah dimodelkan untuk menganalisis profil nadi EDM. Ciri profil nadi adalah
litar terbuka, pelepasan normal, arka dan keadaan litar pintas semasa proses
pemesinan. Model penjana kuasa nadi telah dibentangkan dan dilaksanakan dengan
baik. Fasa-denyut nadi telah dibincangkan yang terdiri daripada fasa awal, fasa
pencucuhan, fasa pembuangan dan fasa ejeksi. Model penjana kuasa denyut telah
disimulasikan dan disahkan oleh hasil kajian sebelum ini.
vii
TABLE OF CONTENT
CHAPTER
1
2
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENT
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF ABBREVIATIONS
xiii
LIST OF SYMBOLS
xiv
LIST OF APPENDICES
xv
INTRODUCTION
1
1.1
Background
1
1.2
Problem Statements
4
1.3
Objectives of Project
5
1.4
Scope of Project
5
1.5
Report Outlines
6
LITERATURE REVIEW
7
2.1
7
Introduction
viii
2.2
Introduction to EDM system
7
2.3
Principle of EDM System
8
2.4
Type of EDM System
10
2.5
Pulse Power Generator for EDM
11
2.6
Power Supply for EDM
12
2.7
Linear Power Supply (LPS)
14
2.7.1 Transformer
16
2.7.2 Rectifier
18
2.7.3 Filter
21
2.8
4
23
2.8.1 RC Pulse Generator
23
2.8.2 Transistor Pulse Generator
24
2.8.3 Types of Pulse Profile
26
2.9
3
Pulse Generator
Previous study on EDM Pulse Power Generator
27
METHODOLOGY
31
3.1
Introduction
31
3.2
Linear Power Supply Model
33
3.3
Pulse Power Generator Model
34
3.3.1 Open Circuit Pulse Profile model
38
3.3.2 Normal Discharge Pulse Profile Model
39
3.3.3 Arc Pulse Profile Model
48
3.3.4 Short Circuit Pulse Profile Model
49
RESULTS AND DISCUSSIONS
51
4.1
Introduction
51
4.2
Simulation of Linear Power Supply
51
4.3
Simulation of Pulse Power Generator
53
4.3.1 Simulation of Open Circuit Pulse Profile
54
ix
4.3.2 Simulation of Normal Discharge Pulse Profile
55
4.3.3 Simulation of Arc Pulse Profile
57
4.3.4 Simulation of Short Circuit Pulse Profile
59
4.4
5
Validation Simulation of Pulse Power Generator
59
CONCLUSION
63
5.1
Conclusion of the project
63
5.2
Future Works
65
REFERENCES
66
Appendix A
69
x
LIST OF TABLES
TABLE NO.
TITLE
PAGE
2.1
Type of EDM
10
2.2
Comparison of LPS and SMPS technology[7][17]
13
2.3
Comparison between Unregulated and Regulated Linear
Power Supply
15
2.4
Comparison performance parameter of rectifier [21]
19
2.5
Interpretation of Percent Ripple [23]
21
2.6
Parameter variable and result
28
4.1
Linear Power Supply Specification
52
4.2
Summarized 4 phase of machining process
53
4.3
EDM Specification
60
4.4
Simulation and Sample of Experiment Data
62
5.1
Summarised pulse profile of EDM
64
xi
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
2.1
Spark generated schematic [5]
9
2.2
EDM System [6]
10
2.3
Die Sinking EDM[10]
11
2.4
Wire EDM[10]
11
2.5
Pulse Power Generator for EDM
12
2.6
Linear unregulated power supply [19]
14
2.7
Block diagram and Unregulated Linear Power Supply[20]
15
2.8
Block diagram and Regulated Linear Power Supply [20]
15
2.9
Transformer with primary and secondary winding
17
2.10
Ideal transformer [19]
17
2.11
Full Bridge rectifier circuit[23]
19
2.12
Operation during positive cycle[20]
20
2.13
Operation during negative cycle[20]
20
2.14
Input and Output of bridge rectifier [19]
21
2.15
Half wave and Full wave rectifier charging and discharging
rate[20]
23
2.16
Relaxation type cicuit[1]
24
2.17
Transistor type of EDM pulse [6]
25
2.18
Relationship Between Duty Cycle and PWM Signal [29]
26
2.19
Pulse Profile of EDM[30]
26
3.1
Project flow chart
32
3.2
Linear Power Supply Block Diagram
33
3.3
Linear power supply model
33
xii
3.4
Transistor type of EDM pulse [6]
34
3.5
Equivalent Circuit Pulse Generator Model
34
3.6
Overall Pulse Power Generator Model
36
3.7
Pulse Generator Model of EDM using MATLAB/Simulink
37
3.8
Equivalent circuit initial phase condition
38
3.9
Open circuit pulse profile model MATLAB/Simulink
38
3.10
Equivalent circuit initial phase condition
39
3.11
Equivalent circuit ignition phase condition
40
3.12
Equivalent circuit discharge phase condition
41
3.13
Equivalent circuit ejection phase condition
46
3.14
Normal Discharge pulse profile model using MATLAB/Simulink 47
3.15
Equivalent circuit discharge phase model
48
3.16
Equivalent circuit ejection phase model
48
3.17
Arc pulse profile model MATLAB/Simulink
49
3.18
Equivalent circuit short circuit model
49
3.19
Short circuit pulse profile model MATLAB/Simulink
50
4.1
Simulation of Linear Power Supply
52
4.2
Simulation Open Circuit Pulse Profile of EDM
54
4.3
Phases of normal discharge pulse profile
55
4.4
Simulation of normal discharge pulse with 4µs ignition delay
56
4.5
Simulation of normal discharge pulse with 10µs ignition delay
56
4.6
Simulation of normal discharge pulse with 16µs ignition delay
57
4.7
Phases of arc pulse profile
58
4.8
Simulation of Arc Pulse Profile of EDM
58
4.9
Simulation of Short Circuit Pulse Profile of EDM
59
4.10
EDM in laboratory
60
4.11
Sample of experiment data during EDM machining process
61
4.12
Discharge pulse profile with different ignition delay
61
4.13
Simulation of pulse profile of EDM during machining process
62
xiii
LIST OF ABBREVIATIONS
EDM
-
Electrical Discharge Machining
AC
-
Alternating Current
DC
-
Direct Current
LPS
-
Linear Power Supply
SMPS
-
Switching Mode Power Supply
RC
-
Resistance Capacitance
MOSFET
-
Metal Oxide Semiconductor Field Effect Transistor
I
-
Current
V
-
Voltage
P
-
Power
xiv
LIST OF SYMBOLS
R
-
Resistance
L
-
Inductance
C
-
Capacitance
𝜋
-
Pi (3.141593)
f
-
Frequency
Ω
-
Ohm
F
-
Farad
Hz
-
Hertz
xv
LIST OF APPENDICES
APPENDIX
A
TITLE
Journal Style Publication
PAGE
67
CHAPTER 1
INTRODUCTION
1.1
Background
With the advancement of technology in the field of space research, missile and
nuclear industry, there is an increased demand for very complicated and precise
component[1]. The need for micro-features, components, and products is rapidly
increasing in diverse industries such as electronics, medical and aviation. Product
miniaturization demands innovative manufacturing methods[2]. This challenge has
been accepted and many new materials and non-conventional methods of machining
have been developed to suit the requirement of the industry[1]. The weaknesses of
traditional or conventional manufacturing method used today have been limited in
their efficiency and ability for these new materials. Therefore, the new approach of
contro system has been invented to deal with this new material that called nonconventional manufacturing method.
Non-conventional methods of machining having several specific advantages
and promise a revolution in the field of technology. These methods capable to produce
any intricate shape and are not affected by the hardness, brittleness, strength and
toughness of a material. This method required an appropriate control parameter,
depending upon the process used for machining. Non-conventional methods of
machining are generally classified into some group as shown in Table 1.1.
2
Table 1.1: Classification of non-conventional methods of machining
Classification
Type
Energy to shape material
Electrical, Chemical, Mechanical
Source of energy for removal
Hydrostatic Pressure, High Voltage,
High Current Density
Medium transfer the energy
High-velocity
particles,
Electrolyte,
Electrons, Hot Gases
Mechanism involved in the processes
Ionic
dissolution,
spark
erosion,
chemical erosion, vaporization
There a few methods have been used for non-conventional machining
processes such as Electrical Discharge Machining (EDM), Electrochemical Machining
(ECM), Plasma Arc Machining (PAM), Ultrasonic Machining (USM) and Electron
Beam Machining (EBM). Table 1.2 shows the application of non-conventional
methods of machining with various work material include aluminum, steel, titanium,
super alloys, refractories, ceramics, glass and plastic. This new invention makes the
efficiency and capability of manufactures are greatly improved.
Table 1.2: Application of non-conventional method of machining with various work
materials [1]
MATERIAL
EDM
ECM
PAM
USM
EBM
Aluminum
Fair
Fair
Good
Poor
Fair
Steel
Good
Good
Fair
Fair
Fair
Titanium
Good
Fair
Fair
Fair
Fair
Super alloys
Good
Good
Good
Poor
Fair
Refractories
Good
Fair
Poor
Good
Good
Ceramics
NA
NA
Good
Good
Good
Glass
NA
NA
Fair
Fair
Fair
Plastic
NA
NA
Fair
Good
Fair
3
Electrical Discharge Machining (EDM) is one of the most accurate nonconventional manufacturing processes used for cutting or creating intricate shapes in
very hard or difficult-to-cut, electrically conducting materials[3]. EDM has been
introduced on this project due to the capability of this non-conventional method
covering a various type of conducting material. EDM is the non-conventional method
that uses electrical energy to shape the material, a high voltage as the source for
removal, electrons as the medium to transfer the energy and spark erosion is the
mechanism involves in the manufacturing process. Various types of products, such as
dies and molds, can be produced by EDM[4]. EDM is one of the most significant
manufacturing processes widely used in the die and mold making industry to generate
an intricate shape, mold cavity, complex shapes[5].
A variability of research work has been carried out on different aspects of EDM
such as tool material-workpiece combination, type of dielectric, pulse train, flushing
techniques and hybridization of EDM with other non-conventional techniques such as
ultrasonic machining, electrochemical machining and abrasive machining. In EDM
process, pulse power generator is required to obtain the discharge spark. The efficiency
of production is depending on the performance of the pulse power generator[6].
Therefore, the selection of pulse power generator is one of the most critical aspects to
take into consideration in EDM manufacturing process. The project has been
conducted to model the pulse power generator that capable to supply a maximum
voltage with the variable current that can be verified by the development of the system.
In this project, the pulse power generator model that consists of the linear power supply
model and a pulse generator model can represent 4 types of pulse profile which are an
open circuit, normal discharge, arc and short circuit during the machining process.
4
1.2
Problem Statements
The efficiency and performance of the EDM process which are the material
removal rate (MRR), surface finish, wear on workpiece and electrode is mainly
determined by the kind of power generator used for EDM machining. The gap
discharge status has a great effect on the machining performance together with the
machining efficiency, material removal rate, surface roughness and tool wear rate in
EDM processes. The final surface finish quality of the workpiece is resolute by the
energy per spark that is applied to the gap. In the EDM process, the rectangular pulses
sensed between the electrodes can be classified into four classes, namely open circuit,
normal discharge, arc and short circuit, correspondingly. An ignition delay has been
used as parameter for gap control in EDM processes. The effectiveness of the EDM
can be controlled by this parameter.
An arc and short circuit condition are an abnormal condition produced by
imperfect flushing of debris and outcome in the incidence of continues sparking on the
same position which could create a large and rough greater size and knowingly affect
the surface quality. An extremely short ignition delay, as an arcing pulse has, usually
portends the weakening of the gap status and instability of an EDM process. An arc
pulses can be attributed to the local overheating in the gap, which makes the dielectric
fluid easier to break down. Usually, arc pulses prime to an ineffective EDM process
and will harm the surface quality in finish machining. In this project, the model of
pulse power generator has been proposed to analyse the pulse profile of EDM during
machining process expecially during an abnormal condition . The model has been
validated with the sample of experiment data.
5
1.3
Objectives of Project
The objectives of this project are as follows
1)
To model pulse power generator using MATLAB/SIMULINK.
2)
To simulate EDM pulse profile during machining.
3)
To analyze pulse profile such as open circuit, normal discharge, arching
and short circuit.
1.4
Scope of Project
To achieve the objective of this project, there are some procedures need to be
designated in this project. The theory involved in designing the device is investigated
before constructing the device. First, the priciple of EDM power generator has been
studying. Power Generator for EDM consists of power supply unit and pulse generator
unit. The model of the linear power supply and pulse generator was modelled and
simulated by using MATLAB/Simulink. The linear power supply was chosen due to
the simplicity, reliability, noise free and cost effectiveness of this power supply. There
are a few types of the pulse generator for EDM system such as RC generator, Rotary
Impulse Generator (RIGS), Controlled Pulse Circuit (CPC) and transistor pulse
generator. Transistor pulse generator was selected because having the facility to
provide higher metal removal rate (MRR) due to its high discharge energy. Beside that
pulse duration and discharge current can be arbitrarily changed depending on
machining characteristic.
The electrical model has been modelled for 4 types of pulse profile which are
an open circuit, normal discharge, arc and short circuit characteristic by using
MATLAB/SIMULINK. Then, the simulation of pulse profile performance during all
6
the condition carried out is analysed and compared with the sample of experiment data
from the laboratory. The limitation of this project is the simulation does not consider
the stochastic nature of EDM process.
1.5
Report Outlines
The thesis consists of five chapters. In the first chapter, it discusses the project
background, problem statement, objectives, scope and report outline.
Chapter 2 presents the background, type of EDM, related work and an
overview of the pulse power generator of EDM. The principle of EDM system and a
previous study on EDM pulse power generator are explained in detail in this chapter.
In chapter 3, the focus is a detailed description of the model of the linear power
supply and pulse power generator. It is clear and concise of work performed. This
chapter describes the sample of experiment data to the model pulse power generator.
In chapter 4, the model of linear power supply, a model of pulse power
generator and a sample of experiment data is attached. This chapter presented
simulation result of pulse power generator model. The analysis and comparison
between simulation and sample of experiment data are obtained to achieve the
objectives of the project.
Lastly, the conclusion of the project is written in the fifth chapter. It also
provides suggestions and recommendations for future wor
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