i EFFECTS OF CHROMIUM POWDER MIXED IN ELECTRICAL …and poor surface quality. EDM becomes most...
Transcript of i EFFECTS OF CHROMIUM POWDER MIXED IN ELECTRICAL …and poor surface quality. EDM becomes most...
i
EFFECTS OF CHROMIUM POWDER MIXED IN ELECTRICAL
DISCHARGE MACHINING OF AISI D2 HARDENED STEELS
MUHAMMAD RIDZUAN BIN IDRIS
Project dissertation submitted in partial fulfilment of the requirement for the Master’s
Degree in Mechanical Engineering
Faculty of Mechanical and Manufacturing Engineering
Universiti Tun Hussein Onn Malaysia
APRIL, 2015
v
ABSTRACT
Nowadays, electrical discharge machining (EDM) is the non-conventional
method that has been used extensively in machining hard material that is commonly
used in mold and die industry but the limitations of EDM will cause lower productivity
and poor surface quality. EDM becomes most apparent by using powder metallurgy
electrode together with chromium (Cr) powder suspension into the dielectric fluid which
has led to the increasing of productivity and good quality performance and
characteristics. Therefore, by combining of both EDM parameters and machining
conditions by incorporating with specific magnetic system plus integrated with existing
filter system, it is highly expected that the machining speed can be enhanced. However,
there are difficulties to determine the best combination of these machining parameters in
order to increase the material removal rate (MRR) and at the same time to reduce the
electrode wear rate (EWR) with the acceptable surface integrity. This research
emphasizes the studies of Cr powder mixed in EDM machining of AISI D2 hardened
steel using copper tungsten electrode which has been done successfully. Data were
analysed using design of three factors at a time consisted of peak current (Ip), pulse-on
(Pon) and powder concentration(C). Discussions were made on the responses such as
MRR, EWR, Surface Roughness (Ra), surface morphology, recast layer (RL) and
microhardness (MH) on the selected samples from the same machining conditions.
Results have proved that Ip was the most significant parameter which has influenced the
machining responses on Cr powder mixed EDM of AISI D2. It is also found that proper
powder concentration of 2gram/litre enhanced the machining efficiency particularly in
MRR. Furthermore, introduction of proper addition of Cr powder in the dielectric also
decreased Ra and RL thickness. The EWR increased as the peak current increased, but
inversely with pulse-on. In general, the possibility of EDM process for machining AISI
D2 tool steel by incorporating Cr powder mixed in the dielectric is acceptable and the
entire objectives were successfully proven.
vi
ABSTRAK
Pada masa kini, mesin nyahcas elektrik (EDM) adalah satu kaedah tidak-
konvensional yang telah digunakan secara meluas di dalam pemesinan bahan keras
yang lazimnya digunakan dalam industri acuan tetapi kekurangan yang ada pada EDM
akan menyebabkan pengeluaran produktiviti yang rendah dan kualiti permukaan
pemesinan yang tidak baik. EDM akan menjadi lebih baik dengan menggunakan
elektrod jenis serbuk metalurgi bersama-sama dengan campuran serbuk kromium (Cr)
ke dalam cecair dielektrik yang boleh meningkatkan produktiviti dan menghasilkan
ciri-ciri pemesinan yang berkualiti. Oleh yang demikian, dengan gabungan kedua-dua
parameter EDM tersebut ditambah pula dengan sistem magnet yang menggantikan
penapis sedia ada dijangka meningkatkan kelajuan pemesinan. Walau bagaimanapun,
terdapat kesukaran untuk menentukan kombinasi parameter yang paling baik untuk
meningkatkan kadar pembuangan bahan (MRR) dan pada masa yang sama
mengurangkan kadar haus elektrod (EWR) dengan integriti permukaan yang boleh
diterima. Kajian campuran serbuk Cr dalam cecair dielektrik diuji dengan keluli keras
AISI D2 sebagai bahan kerja dan menggunakan kuprum tugsten sebagai elektrod telah
dilakukan dengan jayanya. Data akan dianalisis menggunakan reka bentuk daripada
tiga faktor iaitu arus puncak(Ip), kadar denyutan(Pon) dan kepekatan campuran(C).
Tindak balas seperti MRR, EWR, kekasaran permukaan bahan (Ra), morfologi, lapisan
kesan pemanasan haba (RL) dan mikrokeras hasil dari sampel yang dipilih dari keadaan
pemesinan sama akan dibincangkan. Keputusan menunjukkan bahawa Ip adalah
parameter yang paling berkesan mempengaruhi pemesinan. Ia juga mendapati bahawa
tambahan serbuk Cr akan membantu meningkatkan kecekapan pemesinan terutamanya
dalam keputusan MRR. Campuran serbuk Cr dengan kuantiti optimum sebanyak
2gram/liter ke dalam dielektrik akan mengurangkan Ra dan RL. Selain itu, EWR
meningkat kerana peningkatan arus tetapi menurun jika masa denyutan ditambah.
Secara umumnya, sesuatu proses EDM untuk pemesinan keluli AISI D2 dengan serbuk
Cr dicampur dalam dielektrik boleh diterima dan keseluruhan objektif telah terbukti.
vii
TABLE OF CONTENTS
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF FIGURES xii
LIST OF TABLES xvii
LIST OF ABBREVIATIONS AND SYMBOLS xix
LIST OF APPENDICES xxi
CHAPTER 1 INTRODUCTION 1
1.1 Overview 1
1.2 Background of Study 3
1.3 Problem Statement 5
1.4 Objective 6
1.5 Scope 7
1.6 Hypothesis 8
viii
CHAPTER 2 FUNDAMENTAL OF ELECTRICAL
DISCHARGE MACHINING (EDM)
9
2.1 Introduction 9
2.2 Principle of EDM Process 11
2.2.1 Generator Design 12
2.2.2 EDM Control System 14
2.2.3 EDM Process Mechanism 15
2.3 EDM Parameter 17
2.3.1 Electrical Parameter 18
2.3.1.1 Peak Current 18
2.3.1.2 Pulse duration 20
2.3.1.3 Frequency 21
2.3.1.4 Polarity 22
2.3.1.5 Discharge Voltage 23
2.3.2 Non-Electrical Parameter 24
2.3.2.1 Dielectric 24
2.3.2.1 Flushing 25
2.3.3 Powder Mixed EDM 26
2.4 Electrode 30
2.4.1 Metallic Electrodes 32
2.4.1.1 Copper 32
2.4.1.2 Tungsten 33
2.4.1.3 Copper Tungsten 34
ix
2.4.1.4 Brass 36
2.4.1.5 Silver 36
2.4.2 Graphite Electrodes 37
CHAPTER 3 LITERATURE RIVIEW 39
3.1 Introduction 39
3.2 The Fabrication of AISI D2 Hardened Steel 40
3.3 EDM Machining of Hardened Steels 42
3.4 EDM Machining of AISI D2 Hardened Steels 44
3.5 Powder Mixed of EDM machining 55
3.6 Summary 63
CHAPTER 4 METHODOLOGY 66
4.1 Research Design Principles 66
4.1.1 Higher peak current, pulse duration
employed for higher MRR and productivity 68
4.1.2 Filtering system 68
4.1.3 Chromium powder as suspended material 70
4.2 Experimental design and variables 71
4.2.1 Machining parameters 71
4.2.2 Machining characteristic 73
4.3 Research procedures 79
4.3.1 Machining Setup 80
x
4.3.2 Powder Metallurgy Electrode 85
4.4 Equipment and instrumentation 86
4.4.1 Major Instrument 87
4.4.2 Measuring Instruments 88
4.4.2.1 Digital weighting balance 89
4.4.2.2 Surface Roughness Tester 90
4.4.2.3 Tool Maker Microscope 91
4.4.2.4 Scanning Electron Microscope 92
4.4.2.5 Vickers hardness tester 94
4.5 Specimen preparation 95
4.5.1 Sectioning 97
4.5.2 Mounting of specimens 99
4.5.3 Grinding 100
4.5.4 Polishing 101
4.5.5 Etching 103
CHAPTER 5 RESULTS AND DISCUSSION 106
5.1 Material Removal Rate (MRR) 108
5.2 Electrode Wear Rate (EWR) 112
5.3 Surface Roughness (Ra) 117
5.4 Surface Integrity 128
5.4.1 Recast Layer (RL) 128
5.4.2 Microhardness (MH) 139
xi
CHAPTER 6 CONCLUSION 144
REFERENCE 147
APPENDIX 158
xii
LIST OF FIGURES
1.1 Classification of EDM research 2
2.1 Schematic of conventional EDM process 12
2.2 Relaxation circuit 13
2.3 Variation of capacitor voltage with time 13
2.4 EDM spark sequence 15
2.5 Illustration of different usage of current to the different
surface area
19
2.6 Pulse-on with different duty cycle 20
2.7 Pulse-on with different frequency 21
2.8 EDM polarity 22
2.9 Actual profile of a single EDM pulse 23
2.10 Schematic diagrams of the electric discharge for single
power pulse
27
2.11 The material removal mechanism during the normal
discharge for the working fluid
28
2.12 Mechanism of PMEDM 28
2.13 Additive particle behavior 28
2.14 PMEDM spark sequence 29
2.15 Copper electrode 33
2.16 Tungsten electrode 33
2.17 Copper Tungsten electrode 35
2.18 Brass electrode 36
2.19 Silver electrode 37
2.20 Graphite electrode 38
xiii
3.1 EDM setup using CNT 49
3.2 PMEDM schematic for dispenser and pump system. 50
3.3 Diagram of a self-designed filter system for the EDM. 52
3.4 Typical waveform of voltage and current: 59
3.5 Discharging waveform of voltage 60
3.6 The apparatus used to produce a single discharge 61
3.7 Comparison of crater morphology at various machining
parameters
62
3.8 Micrographs of crater generated by a single pulse discharge 63
4.1 Overall research methodology 67
4.2 Illustration of powder and debris motion in PMEDM
process
69
4.3 Ishikawa Cause-Effect Diagram 72
4.4 Two categories of machining characteristic 73
4.5 Specimen test preparation 74
4.6 Experimental process flowchart 79
4.7 Experiment setup for HPEDM 81
4.8 Image for HPEDM 84
4.9 Sodick AQ55L 88
4.10 Mettler Toledo PL403 precision balance. 89
4.11 Mahr Perthometer PGK-120 90
4.12 Tool Maker Microscope Nikon MM-60 91
4.13 Scanning Electron Microscope (Joel-JSM 6380 L.V) 93
4.14 Vickers tester 95
4.15 Specimen preparation 97
4.16 Abrasive cut-off machine (Stuers Lobotom 3) 98
4.17 Specimens after compression mounting 99
4.18 Buehler Auto Mounting Press machine 100
xiv
4.19 Buehler Roll Grinder 101
4.20 Polish machine 102
4.21 Bright field illumination 104
4.22 Dark field illumination 105
5.1 Effect of powder concentration and pulsed duration on
material removal rate [Ip=20A]
110
5.2 Effect of powder concentration and pulsed duration on
material removal rate [Ip=32A]
110
5.3 Effect of powder concentration and pulsed duration on
material removal rate [Ip=40A]
110
5.4 Effect pulsed duration and powder concentration on
electrode wear rate [Ip=20A]
114
5.5 Effect pulsed duration and powder concentration on
electrode wear rate [Ip=32A]
114
5.6 Effect pulsed duration and powder concentration on
electrode wear rate [Ip=40A]
114
5.7 Surface morphology of electrode with different pulse-on 116
5.8 Effect pulse duration and powder concentration on surface
roughness [Ip=20A]
119
5.9 Effect pulse duration and powder concentration on surface
roughness [Ip=32A]
119
5.10 Effect pulse duration and powder concentration on surface
roughness [Ip=40A]
119
5.11 Surface morphology of D2 workpiece at increasing peak
current [Pon=50µs, C=2g/l]
121
5.12 Surface morphology of D2 workpiece at increasing pulse-
on [Ip=20A, C=2g/l]
123
5.13 Surface morphology of D2 workpiece at an increasing
powder concentration [Ip=40A, Pon=50µs]
125
5.14(a) Surface texture of EDM workpiece for maximum and
minimum surface roughness
127
xv
5.15 Effect Pulse-on and Powder concentration on Recast layer
at Peak current [Ip=20A]
130
5.16 Effect Pulse-on and Powder concentration on Recast layer
at Peak current [Ip=32A]
130
5.17 Effect Pulse-on and Powder concentration on Recast layer
at Peak current [Ip=40A]
130
5.18(a) Optical microscope showing the cross-sectional view of the
recast layer of the EDM machined surface layer
[Pon=100µs, C= 2g/l, Ip=20A]
132
5.18(b) Optical microscope showing the cross-sectional view of the
recast layer of the EDM machined surface layer
[Pon=100µs, C=2g/l, Ip=40A]
132
5.18(c) SEM showing the cross-sectional view of the recast layer of
the EDM machined surface layer [Pon=100µs, C= 2g/l,
Ip=20A]
133
5.18(d) SEM showing the cross-sectional view of the recast layer of
the EDM machined surface layer [Pon=100µs, C=2g/l,
Ip=40A]
133
5.19(a) Optical microscope showing the cross-sectional view of the
recast layer of the EDM machined surface layer [Pon=50µs,
C= 0g/l, Ip=32A]
134
5.19(b) Optical microscope showing the cross-sectional view of the
recast layer of the EDM machined surface layer[Pon=100µs,
C= 0g/l, Ip=32A]
134
5.19(c) SEM showing the cross-sectional view of the recast layer of
the EDM machined surface layer [Pon=50µs, C= 0g/l,
Ip=32A]
135
5.19(d) SEM showing the cross-sectional view of the recast layer of
the EDM machined surface layer[Pon=100µs, C= 0g/l,
Ip=32A]
135
xvi
5.20(a) Optical microscope showing the cross-sectional view of the
recast layer of the EDM machined surface layer [Pon=75µs,
C= 0g/l, Ip=20A]
137
5.20(b) Optical microscope showing the cross-sectional view of the
recast layer of the EDM machined surface layer [Pon=75µs,
C= 2g/l, Ip=20A]
137
5.20(c) SEM showing the cross-sectional view of the recast layer of
the EDM machined surface layer [Pon=75µs, C= 0g/l,
Ip=20A]
138
5.20(d) SEM showing the cross-sectional view of the recast layer of
the EDM machined surface layer [Pon=75µs, C= 2g/l,
Ip=20A]
138
5.21 Microhardness of Sub-surface layer of workpiece at
different Powder concentration [Ip = 40A, Pon = 100s]
140
5.22 Microhardness of Sub-surface layer of workpiece at
different Peak current[C = 2g/l, Pon = 100s]
141
5.23 Microhardness of Sub-surface layer of workpiece at
different Pulse-on [Ip = 40A, C = 2g/l]
143
xvii
LIST OF TABLES
2.1 Advantages and limitations of EDM 10
2.2 Electrode material properties that effect EDM 31
2.3 Physical properties and miscellanea of copper and tungsten 35
3.1 Chemical composition of AISI D2 hardened steel 40
3.2 Physical properties of AISI D2 hardened steel 40
3.3 Procedure of heat treatment for AISI D2 hardened steel 41
4.1 Specifications of powder used 70
4.2 Thermophysical properties of powder used 70
4.3 Machining parameter 72
4.4 Experimental Design and Response 75
4.5 Data collection sample of material removal rate of each
composition of powder concentration and peak current (Ip)
setting
76
4.6 Data collection sample of tool wear rate of each
composition of powder concentration and peak current (Ip)
setting
77
4.7 Data collection sample of surface roughness of each
composition of powder concentration and peak current (Ip)
setting
78
4.8 Data collection sample of average micro-hardness of each
composition of powder concentration and peak current (Ip)
setting
78
4.9 Summary PMEDM part 82
xviii
4.10 The specification of Nikon MM-60 (Tools Maker
Microscope)
92
4.11 The specification of SEM (JSM 6380) 93
5.1 Overall Result of EWR, MRR, Ra and RLwith different peak
current, pulsed on duration and powder concentration
107
5.2 Results of material removal rate (MRR) with different peak
current, powder concentration and pulsed on duration
109
5.3 Result of electrode wear rate (EWR) with different peak
current pulsed on duration and powder concentration
113
5.4 Result of surface roughness (Ra) with different peak current,
powder concentration and pulsed on duration
118
5.5 Result of Recast Layer (RL) with different peak current,
powder concentration and pulsed on duration
129
6.1 Summary of optimum MRR, EWR and Ra 146
xix
LIST OF ABBREVIATIONS AND SYMBOLS
Al - Aluminium
AISI - American Iron and Steel Institute
C - Powder concentration
CNT - Carbon nano tube
Cr - Chromium
CV - Control valve
CuW - Copper tungsten
EDM - Electrical discharge machining
EWR - Electrode wear rate
FPGA - Field-programmable get array
HAZ - Heat affective zone
HRC - Hardness Rockwell unit for steel
Ip - Discharge current
MRR - Material removal rate
PMEDM - Powder mixed dielectric electrical discharge machining
Pon - Pulse duration
PLC - Programmable logic controller
PM - Powder metallurgy
SEM - Scanning electron microscopy
SA - Surface area
SI - Surface integrity
SiC - Silicon carbide
TELCO - Tellurium copper
Ra - Surface roughness
RL - Recast layer
xx
tm - Machining times
Wa - Weight of workpiece after machining
Wb - Weight of workpiece before machining
xxi
LIST OF APPENDICES
Apendix A List of Publication Related
Apendix B A Summary of Literature Review on EDM Die Sinking
(AISI D2 Hardened Steel)
1
CHAPTER I
INTRODUCTION
1.1 Overview
Following the technology of manufacturing today, machining process is dealing with
challenges from the marketing demand that needed to requires the use of advanced
materials such as composite, super alloys, and hardened steels that are so hard to be
machined. The high speed machine that can produce good surface integrity and precise
cutting with less tool wear, are among the criteria to use in the advance technology, i.e.
aerospace, automotive and medical material. Since it is impossible to use conventional
machining of hard material, non-conventional machining such as electrical discharge
machining (EDM) is one of the ideal techniques in dealing with these materials
including hardened steel.
EDM is generally known as a ‘vertical’, ‘ram’ or ‘sinker’ electrical discharge
machining that has been used in the industry over fifty years ago. According to the
current world developments, EDM has also increased technology that enables the EDM
to produce superficial, thin and compact mechanical elements that are used by the
advanced manufacturer. The power supply on a previously effective EDM has improved
according to the changes in electric and electronic fields. It is capable to produce more
power efficiently, generate various types of waves and high frequency. Due to the
2
existence of rapidly growing control systems, EDM is suitable for producing work that
requires a high level of accuracy. Most of EDM use computer numerically method
(CNC) as their programming to communicate with human to improve the machining
process.
EDM is a machine that can provide many benefits for high accuracy and
precision of machining process. It requires further research to produce a more realistic
EDM. Numerous researchers have optimized the process variable to improve the
machining workpiece characteristics such as by increasing the material removal rate due
to increase in machining speed, increasing the tool life and obtain the best surface
integrity. Some of the researchers modified the EDM system to fulfill the requirement
global trend of machining process. Figure 1.1 shows some of the research area in EDM.
Figure 1.1: Classification of EDM research (Pandey and Singh, 2010)
High potential of EDM can help to improve productivity in the industry. Productivity
is one of the important elements in the industry today. Higher productivity can lead to
improved industry performance such as lower average costs, higher profits, higher
EDM ResearchArea
Improve PerformanceMeasure
EDMApplication
Area
HybridMachining
Process
SurfaceRoughness
EWRMRR
PMEDM
USEDMECDM
Pulse-on Peak Current Discharge
Voltage Polarity
Rotational Speed Flushing Pressure Volume Friction of
Powder Mixed
Electrode DesignModification
Optimization ofProcess Variable
EDMDevelopment
Incr
ease
Red
uce
Red
uce
3
wages and improved competitiveness and trade performance. Hence, to fulfill this
demand, the machines in the industry must have a high speed productivity including
EDM.
1.2 Background of Study
Electrical discharge machining (EDM) is the non-conventional method that has been
used extensively in the machining process of hard material that is commonly used in
mold and die industry. The basic process of EDM is to remove metal through the action
of an electrical discharge energy and high current intensity between the tool (electrode)
and the workpiece without physical cutting force. This is one of the advance methods to
replace traditional machine method that able to machine difficult-to-cut or hard materials
such as titanium, inconel and hardened steel. It can be successfully employed to
electrically conductive machine parts regardless of their hardness and toughness. In spite
of remarkable process capabilities, limitations such as low volumetric material removal
and poor surface quality are associated with EDM (Kansal et al, 2007).
Limitation of EDM will cause lower productivity, which is due to low cutting
speed. In that case, researchers of EDM explored a new method to improve the sparking
efficiency phenomenon including some modification of experimental concepts and their
existing system. The researchers needed to consider the machining process condition
and parameters such as discharge voltage, peak current, pulse-on, flushing and dielectric
medium before executing the new method of the machining process. To date, most of
the studies in EDM have undergone the normal effect of machining process condition
which applies low level of machining parameters. Yet, few studies have been
implemented in greater current and long pulse-on and at the same time to maintain the
EDM machining stability and efficiency to obtain the best material removal rate (MRR),
lower electrode wear rate (EWR) and the good performance of the workpiece surface
4
integrity. Therefore, there is a keen interest to look forward into this new phenomena in
EDM machining and hence for greater productivity.
Nowadays, research becomes most apparent by using powder metallurgy
electrode together with powder suspension into the dielectric fluid which has increased
the productivity, and good quality performance and characteristics. Therefore, by using a
combination of both EDM parameters and machining process conditions, and
incorporating with the specific magnetic system plus integrated with the existing filter
system, it is highly expected that this combination can enhance the machining speed.
The filter system integrated with magnetic force is used to separate debris or
contaminants from dielectric fluid and hence the efficiency of spark erosion becomes
more stable and easy to cut the materials. In order to realize the full potential of new
setting of EDM machining by incorporating magnetic and pump system, the new
dielectric tank was developed which was integrated with a continuous circulation
system.
Many studies have been applied through this process in several types of
materials, but lack of work has been carried out to incorporate powder mixed in the
EDM machining of AISI D2 hardened steels. It is also found that a comprehensive study
in EDM machining of AISI D2 is still scarce. New machining data on the EDM of AISI
D2 serves a great significance and could be further exploited especially for hole making
operation. Further research on powder mixed EDM machining mechanism and its
characteristics of this kind of material is expected to give better rate and efficiency of the
machining process. This project was undertaken to study the effect of machining process
conditions and incorporated with powder mixed in EDM machining of AISI D2
hardened steels and by employing advanced powder metallurgy electrode of copper
tungsten (CuW).
5
1.3 Problem Statement
The low cutting speed for machining process of difficult-to-cut material which is due to
low productivity of electrical discharge machining (EDM) is one of the EDM
limitations. According to this problem, researchers associated to EDM have explored a
new method to improve the efficiency and cutting speed of the machining process
including some modification of experimental concepts to improve their existing system.
The machining process condition and parameters such as discharge voltage, peak
current, pulse-on, flushing and dielectric medium, need to be considered before
executing the new method or some modification.
In EDM process, the pulse-on, peak current and dielectric condition are among
the very important machining parameters because they can directly control the result of
material removal rate (MRR), electrode wear rate (EWR), surface roughness (Ra) and
surface integrity. However, there are difficulties to determine the best combination of
these machining process parameters to increase the MRR and at the same time to reduce
the EWR with the acceptable surface integrity. In addition, the unsuitable dielectric
condition used with longer pulse-on and higher peak current will also increase the
production cost. The high hardness properties of AISI D2 hardened steel and high wear
of tool electrode EDM material will also affect the performance of EDM machining
characteristic. Therefore, it is estimated that by incorporating Chromium (Cr) powder in
the dielectric fluid can deliver better result in terms of material removal rate, electrode
wear rate and acceptable surface integrity in machining process of AISI D2 hardened
steel. Likewise, the use of copper tungsten (CuW) electrode is also expected to deliver
minimum EWR and maximum MRR in the Cr suspended dielectric electrode.
6
1.4 Objective
The aim of the research is to investigate the effect of machining process parameter at
different concentration of Chromium (Cr) powder mixture of dielectric in electrical
discharge machining (EDM) machining of AISI D2 hardened steel with specific aims:
i). To determine the effect of machining process parameter on the following
machinability such as electrode wear rate (EWR), material removal rate (MRR)
and surface roughness (Ra).
ii). To identify the effect of machining process parameter on the following
machining characteristics such as;
a) Topmost workpiece surface morphology
b) Subsurface layer changes which include recast layer (RL) and heat
affected zone (HAZ)
c) Microhardness at deeper layer of the machined surface
iii). To explore the performance of powder mixed dielectric in EDM machining of
AISI D2 hardened steel.
1.5 Scope
i. Electrical discharge machining (EDM) die sinking AQ55L Sodick machine is
used to carry out the experiments designed.
ii. The main parameters investigated are: powder concentration and pulse-on.
a) Peak current: 20A, 32A, 40A.
b) Powder concentration: 0g/l, 2g/l, 4g/l.
c) Pulse-on: 50µs, 75µs, 100µs.
iii. Powder metallurgy tool electrode (W-Cu: Copper-Tungsten 35%C65%W) is
selected as the cutting tool for machining the work piece.
7
iv. The machining process operation is conducted on AISI D2 hardened steel
(having a typical hardness range of 56-62 HRC) as work material.
v. The experiment is carried out in hydrocarbon oils (i.e. Kerosene) as a dielectric
medium with Chromium (Cr) powder suspended.
vi. Magnetic system attached with filter system is applied in the EDM machine.
vii. Experimental trials are conducted to investigate and evaluate the following
responses:
a) Subsurface layer changes which include recast layer (white layer) and
heat affected zone (HAZ) using scanning electron microscope (SEM)
b) Microhardness at deeper layers of the machined surface using the Vickers
Hardness Tester
c) Machining removal rate and tool electrode wear rate by Digital Weighing
Machine
d) Workpiece morphology by SEM
viii. Collection of data through experiments are analyzed with:
a) Observation of machining process characteristics of workpiece materials
due to surface modification. The machining process characteristics are
composed of EWR, MRR, Ra and RL.
b) Evaluation and comparison of the effect of cutting conditions on the
machinability of the cutting tool material with the effects of workpiece
surface modification or alteration.
1.6 Hypothesis
Powder mixed of electrical discharge machining (PMEDM) is one of the methods to
improve the quality of the machined component. It is expected that the investigation on
machining process performance for different concentration of Chromium (Cr) powder
of PMEDM will determine the best amount of Cr powder concentration in the machining
process of AISI D2 hardened steel particularly for high productivity of EDM machining
8
operation. The introduction of Cr powder as an additive in dielectric can help to
improve the machining process capability to remove material from workpiece material
efficiently. This research concentrates on high productivity of machining process by
achieving faster and more efficient metal removal rate (MRR) by using higher peak
current and pulse-on without compromising the electrode wear rate (EWR) and surface
machining characteristics. In addition, the evaluation of surface morphology images
using scanning electron microscope (SEM) will give good information about the
characteristics of the workpiece after machining process. Hence, the information could
be used to analyze the electrode and surface integrity of the machined workpiece
surface.
9
CHAPTER II
FUNDAMENTAL OF ELECTRICAL DISCHARGE
MACHINING
2.1 Introduction
The history of electrical discharge machining (EDM) goes far back to the 1770’s when
an English scientist named Joseph Priestly, discovered the eroding effect of electricity
on various metals. Based on Priestley’s research, the soviet researchers named
Lazarenko B. R and Lazarenko N.I had the idea to use the destructive effect of the
electrical charge for difficult-to-cut machining. In 1943, they developed the discharge
generator of EDM known as Larazenko Circuit. It is based on the relaxation or RC
circuit that was used today. They also developed a working procedure with spark
erosion, where electrical discharges in a dielectric liquid take place between two
conductors (Fleming, 2005). Since the introduction of EDM over fifty years ago, the
technology for speed and precision has grown tremendously and, likewise, its capability
and manufacturing applications have followed suit (Guitrau, 1997).
EDM is one of the non-traditional machining process that uses electrochemical
concept, where electrical energy is used to generate an electrical spark and vaporizing a
part of the material. The material removal mainly occurs due to the thermal energy of
the spark. In fact, EDM can create precise shapes, burn-free and intricate in machining
material. Because of that, EDM has been widely used not only in molds and dies, but
10
also in aerospace application, making extrusion dies and production in small holes.
EDM is selected in many cutting applications because of the advantages offered over the
conventional method, but EDM is available only for conductive material. The
advantages and limitations of EDM are listed in Table 2.1.
Table 2.1: Advantages and limitations of EDM
Advantages Limitation
EDM can be used to all conductive
materials
The workpiece must be conductive
Able to create complex shapes Slower material removal rate for hard
material
No force between tool electrode and
workpiece
Electrode wear may require the use of
several tools
Automated Undesirable recast layer needs to be
removed
High precision machine Equipment is expensive
Repeatability Leave a very shallow, highly stresses,
surface layer
High accuracy machine Cavities may slightly taper
EDM has been proven to be applicable for electrically conductive machine
materials such as carbide, stainless steel, hastalloy, naturally, waspalloynomonic and
others regardless of their physical and metallurgical properties (Kumar et al., 2011).
EDM technology is expanding as being used in tool, dies and mold making industries for
machining process of heat treated tool steel and advanced material (super alloys,
ceramics and metal composites) which require high precision, complex shapes and high
surface finish (Prabhu and Vinayagam, 2008). This has made the EDM technology to
grow with more accurate and dependable process.
11
2.2 Principle of EDM Process
Electrical discharge machining (EDM) is a process that uses electrical discharge to
remove metal from the workpiece. The electrode and workpiece are separated by a small
gap and connected to the power supply probe. These two parts are immersed in dielectric
fluid such as kerosene which is functioning as integral to the process. By applying high
frequency of AC or DC current to workpiece through an electrode, the workpiece melts
and vaporizes. Positioned very precisely near the workpiece, the electrode never touch
the workpiece but discharges its potential current through an insulating fluid (dielectric)
across a very small spark gap (Guitrau, 1997). The electric spark is generated and
controlled by a machine power supply.
An EDM system comprised of a generator, servo system, dielectric fluid system
and dielectric work tank. Figure 2.1 shows the schematic diagram of EDM system. The
workpiece is placed in the dielectric tank and affixed to the metal plate in the tank. The
tank is filled with hydrocarbon dielectric which is ionized in the presence of an electrical
field. The dielectric fluid breakdown electrically, after short ionization period, assuming
that the electricity is high enough. The electric field is created by applying voltage
between electrode and workpiece. The breakdown of dielectric fluid is much like the
breakdown of air when the large voltage is supplied from coil in an automotive ignition
system to the spark plug (Fleming, 2005). The spark of EDM is reported to be in the
range of 8000C to 12000C (14432F to 21632F), and it vaporizes and melts the
workpiece material (Guitrau, 1997).
The effect of using EDM machining is that the ‘chip’ from the workpiece is
produced and not allowed to accumulate at the workpiece. Flushing is needed to flush
away the ‘chip’ and debris from the spark gap because the accumulated debris will
disturb the machining process. The debris is filtered by the EDM filter to maintain the
cleanliness of dielectric in the work tank.
12
Figure 2.1: Schematic of conventional EDM process
2.2.1 Generator Design
The electrical discharge machining (EDM) generator is the device to control electrical
discharge. In 1943, B.R and N.I Lazarenko exploited the destructive effect of an
electrical discharge machining and developed the relaxation circuits known as lazarenko
relaxation (RC) circuit. They realized that the spark energy would have to be harnessed
and controlled if the discharges are to be efficiently utilized for machining (McGeough,
1988). Figure 2.2 below shows relaxation or RC circuit. The electrical energy of the
capacitor is charged from the DC source voltage until it breaks down and discharges into
the electrode and workpiece that are immersed in the dielectric fluid. Figure 2.3 below
shows the output voltage generated by relaxation circuit.
FILTER
PUMP
DIELECTRICFLUID SYSTEM
DIELECTRIC
MACHININGSERVO HEAD
POWER SUPPLY
HYDRAULICPOWER UNIT
RESERVOIR
MACHINE TOOL
WORKPIECE
WORKTANK
ELECTRODE
13
Figure 2.2: Relaxation circuit (Lazarenko,1943)
Figure 2.3: Variation of capacitor voltage with time.
The basic of EDM generator is the controlled pulse generator. The pulse
generator system can control their ON/OFF time, frequency and current level. The
advantages of pulse generator are the electrode wear can be greatly reduced and higher
metal removal rate under certain condition (Fleming, 2005). The development of control
pulse generator has been improved every decade and century. Their efficiency has
improved from 33% (1970) to >80% (today). With the development of electronics power
system, the power supply of EDM is now using field programmable get array (FPGA), a
technology that can control the distance of spark gap tightly, high frequency and high
current and constant result. The EDM generator has improved drastically which is
Chargingvoltage,V
BreakdownVoltage Vc
Gap filled with
dielectricWorkpiece
Toolelectrode
DC voltagesource
Resistor
Capasitor
Voltage Vc
Capasitorvoltage
Time
14
progressing from RC circuit power supply and vacuum tubes to solid-state-transistor
with nanosecond pulsing (Guitrau, 1997).
2.2.2 EDM Control System.
Almost all of EDM machining use drive system in their manufacturing. Some builders
use stepper motors and others use servo motor. With the presence of sophisticated
technology today, high resolution of an encoder can move the electrode in micron scale.
To support the increase in technology movement that can produce high potential
machine, this driver must be provided. Over the past few years, the trends in control
system have grown from 16 bit to 32 bit processor for increasing the computing speed
(Guitrau 1997).
The investigation of the control systems of EDM machines has been an
important effort in the field of electric discharge machining. Each EDM can be seen as a
stochastic time-dependent nonlinear system involving many parameters. Applications
mainly include those situations when the conventional controls of linear, constant
coefficient systems could not produce adequate outcomes. The current commonly
employed EDM control systems are established on the modern control theory. The
control systems often applied as self-adaptive control systems generally employ the
mathematical models estimates accompanied by high costs without actually realize the
truly significant optimal results (Liu, 2010).
Some ram machines are equipped with fuzzy logic. Unlike bilevel logic, which
recognizes a statement as either true or false, fuzzy logic allows a statement to be
partially true or false. Fuzzy logic allows the machine to think and react quickly to
various machining conditions. This machine can lower the increased power setting to
obtain the optimum combination of speed, precision and finish. Fuzzy logic system will
constantly control the power setting to maximize the efficiency (Sommer, 2005).
15
2.2.3 EDM Process Mechanism
In electrical discharge machining (EDM), the removal of material is based upon the
effect of electro discharge erosion of electric spark occurring between the electrode and
workpiece separated by dielectric as their type of gap. The spark is unstable, irreversible
and transient phenomenon sometimes marked the transition from a state of more or less
stable for the current between the electrodes in the gas to other more stable under
conditions imposed (Leonard and Meek, 1941). For the EDM process, the transition
spark from the electrode will occur because the condition of the workpiece is more
stable. An electric spark is a type of electrostatic discharge that occurs when an electric
field creates an electrically conductive ionized channel in the air producing a brief
emission of light and sound. A spark is formed when the electric field strength exceeds
the dielectric field strength of air (Leonard and Meek, 1941). Figure 2.4 shows the
illustrations of relative values of voltage and current at the represented point and the
description of the process.
Process Description
(a)
“Open-Gap” voltage. The electrode is seeking
the workpiece while “cutting air”. The graph
shows high potential voltage only and no
current. Time line runs horizontal. The
capacitor starts to charge until voltage
breakdown.
(b)
Displays the electromagnetic field created
between electrode and workpiece. Dielectric
within this field becomes polarized as
resistance decreases. Voltage level off because
capacitor stop to charge.
16
(c)
“On-time” begins. Dielectric resistance is
overcome and the spark occurs, generating
current which vaporizes the workpiece. As
amperage increases, voltage decreases.
(d)
The spark is plasma hot and enclosed within a
sheath of gases. Vaporization of workpiece
continues.
(e)
Gas bubble continues to expand rapidly (vapor
pressure). At a certain point, vaporization will
cease and melting begins. Dielectric
contamination increases.
(f)
Amperage and voltage have leveled off as
contamination and thermal damage of dielectric
increase. Dielectric is now severely
compromised and its electrical resistivity
continues to rise. If allowed to continue,
conditions will cause “DC arcing”.
17
(g)
Power is interrupted during “off time” part of
EDM cycle. Current drops to zero. The gas
bubble collapses upon removal of heat source.
(h)
Gases and contaminated dielectric will
naturally disperse, but using forced or sealed
flushing is the best method and will
significantly reduce dielectric recovery time
and increase cutting speed.
(i)
Contamination and damaged dielectric are
expelled, revealing EDM crater on workpiece
and wear on the electrode. Dielectric begins
reionization, allowing a repeat of the cycle.
Figure 2.4: EDM spark sequence
2.3 EDM Parameter
In EDM process, various input parameters affected the measured experimental
parameter. Electrical parameter on EDM can controlthe power supply system or
generator of EDM machine, while non-electrical parameter is not related to discharge
energy such as flushing and dielectric type. Each distinctly different, but must be used
18
together in different combination to obtain the desired result (Guitrau, 1997). Generally,
EDM parameters consist of two functional groups which are:
i) Electrical parameter
(a) Peak current
(b) Pulse-on
(c) Frequency
(d) Polarity
(d) Discharge voltage
ii) Non electrical parameters
(a) Flushing
(b) Dielectric
2.3.1 Electrical Parameter
Major electrical parameters are discharged voltage, peak current, pulse-on and pulse
interval, pulse waveform and polarity. The EDM process is a stochastic thermal nature
which has complicated discharge mechanism. Therefore, it is difficult to explain all the
effect of these parameters on performance measures. However, researchers are now
relying on the process analysis for optimization of parameters to identify the effect of
operating variables in achieving the desired machining characteristics.
2.3.1.1 Peak Current
Current is the amount of power used in the electrical discharge machining. The
utilization of current in EDM is related to the area of machining “cut”. It is like cutting
wood, if we cut a thick wood, we need a lot of energy to swing the ax. The greater
amount of surface area needs more power to cut. According to Guitrau (1997), the
19
maximum power selection is approximately 65 amps per square inch of electrode
engagement. This is a simple formula to be based upon surface area (SA) of electrode
engagement multiplies by a constant of 65 amps per square inch or
Surface Area(SA) 65 = maximum amperage (2.1)
Based on the formula, the electrode has an area of 0.1 inch and 0.2 inch, 6.5A
and 13A current, respectively. Figure 2.5 below shows the illustration of different usage
of current to different surface area (Guitrau, 1997).
Figure 2.5: Illustration of different usage of current of the different surface area
Dc source
Dc source
Dc PulseCurrent
6.5A
13A
Dc PulseCurrent
Dc PulseCurrent
0.1”Electrode
Workpiece
0.2”Electrode
Workpiece(a)
(b)
20
2.3.1.2 Pulse Duration
Knowing the EDM process and how it works is not enough. The pulse duration of EDM
needs to be explored because it relates to know how to get good machining speed and
good finishes with minimum wear, high machining rate and the lowest possible chance
of d.c arcing. The pulse duration is controlled by pulse generator that can adjust the
value of ON time and OFF time. In the ON-time cycle, current is generated and spark
gap is bridged, and the work accomplishes. The longer duration of ON-time will create
the longest spark and this will cause more workpiece material to melt. With the
occurrence of longer discharge energy, the resulted creators will be broader and deeper,
therefore the surface finish will be rougher. In positive polarity, the spark leaves
electrode and strikes the workpiece. More sparks produced within a unit time will
produce proportionately wear. OFF-time is the duration of rest required for reionization
of dielectric. The longer period of OFF-time is not good because the process will take
longer time, but the machine stability increases (Guitrau, 1997). The ON-time as a
percentage of total cycle time (inverse of the frequency) is call duty cyle. Figure 2.6
shows three examples of pulse-on with different duty cycle.
(a)
(b)
(c)
Figure 2.6: Pulse-on with different duty cycle (a)25% (b)50% (c)75 % (Guitrau, 1997)
50µs
0
0
I
OFF-time
I
I
025µs
25µs
50µs
0
25µs
ON-time25µs
21
2.3.1.3 Frequency
Frequency is the number of total cycles in one second. Low frequency is usually used in
the roughing operation because it consists of long pulse-on of the spark that yield a
larger, deeper and broader crater. In addition, the recast layer will be thicker and Heat
Affected Zone (HAZ) is deeper because of the length of heat transfer. While, high
frequency is usually for finishing state that can reduce the size of the crater and less
recast (Guitrau, 1997). Figure 2.7 shows three different frequencies of pulse-on.
(a)
(b)
(c)
Figure 2.7: Pulse-on with different frequency (a)low (b)moderate (c)high
(Guitrau, 1997)
100µs
ON
CURRENT
OFF
f=6.67 KHz
50µs
50µs
200µs
ON
CURRENT
OFF
f=4 KHz
50µs
f=10 KHz
50µs
ON
CURRENT
OFF
22
2.3.1.4 Polarity
This parameter determines electric polarity of the electrode and the workpiece. Polarity
refers to the direction of current flow in relation to the electrode (Sommer, 2005).
Polarity can be either reverse (positive) or normal (negative). Polarity can affect speed,
finish, wear and stability. In most cases, positive polarity (reverse polarity) will machine
slower than negative polarity. Despite this disadvantage, positive polarity is often used
to protect the electrode from excessive wear (Fleming, 2005). According to the research
from Khan (2011), higher metal removal rate and lower relative electrode wear are
achieved with normal polarity (positive polarity) but better surface finish is achieved
with reverse polarity (negative polarity). Figure 2.8 shows normal polarity and reverse
polarity in EDM.
(a) (b)
Figure 2.8: EDM polarity (a) Reverse polarity (b) Normal polarity
+ve
Electrode
Workpiece
-ve
PL=-
-ve
Electrode
Workpiece
PL=+
+ve
23
2.3.1.5 Discharge Voltage
Discharge voltage in Electrical Discharge Machining (EDM) is related to the spark gap
and break-down strength of the dielectric (Kansal et al., 2005). Prior to flow of current,
the open gap voltage increases until it has created an ionized path through the dielectric.
Once the current starts to flow, the voltage drops and stabilizes at the working gap level.
The preset voltage determines the width of the spark gap between the leading edge of the
electrode and workpiece. Higher voltage settings increase the gap, which improves the
flushing conditions and helps to stabilize the cut. Electrode wear rate (EWR) and surface
roughness increase by increasing the open circuit voltage because the electric field
strength increases. However, the impact of changing open circuit voltage on surface
hardness after machining has been found to be only marginal (Kansal et al., 2005).
Figure 2.8 shows the actual profile of the single EDM pulse; (a) ionization time, (b)
discharge time, (c) deionization time, and (d) idle time.
Figure 2.9: Actual profile of a single EDM pulse (Fuller, 1996).
On-Time Off-Time
Voltage
Current
Time
a b c d
24
2.3.2 Non-Electrical Parameter
Main non-electrical parameters are flushing the dielectric and type of dielectric. These
non-electrical parameters play a critical role in optimizing the performance measures.
Researches on flushing pressure revealed that it affects the surface roughness, tool wear
rate, acts as a coolant and also plays a vital role in flushing away the debris from the
machining gap (Leonardo and Bruzzone, 1999). Workpiece rotary motion improves the
circulation of the dielectric fluid in the spark gap and temperature distribution of the
workpiece yielding better material removal rate (MRR) and surface roughness (Guu and
Hocheng, 2001).
2.3.2.1 Dielectric
Basic characteristics required for dielectric used in EDM are high dielectric strength and
quick recovery after a breakdown (Wong et al., 1995). The dielectric oils are the best
coolant for most of the EDM machining and impact for machining speed. In EDM,
material removal mainly occurs due to thermal evaporation and melting as thermal
processing is required to be carried out in the absence of oxygen so that the process can
be controlled and avoid oxidation. Oxidation often leads to poor surface conductivity
(electrical) of the workpiece hindering further machining. Hence, dielectric fluid should
provide an oxygen free machining environment. Further, it should have enough strong
dielectric resistance so that it will not electrically breakdown too easily, but at the same
time ionizes when electrons collide with its molecule. Moreover during sparking, it
should be thermally resistant as well (Dewangan, 2010). The sinker EDM process has
primarily used oil in the dielectric fluid. According to Roger Ken from EDM Magazine
Today, the dielectric oil in a Sinker EDM serves a number of functions:
• The dielectric oil acts as a medium through which control the occurrence of
electrical discharges.
147
REFERENCES
Ahsan, A.K., Mohammad Y.A. and Md. Mohafizul H., (2009). A study of electrode
shape configuration on the performance of die sinking EDM. Int J Mech& Mat
Eng (IJMME), Vol. 4, No.1, 19 - 23.
Angelo P. C. and Subramanian R. (2008). Powder Metallurgy: Science, Technology
And Applications, PHI learning private limited India
Amorim and Weingaertner (2005). The influence of generator actuation mode and
process parameters on the performance of finish EDM of a tool steel. Journal of
Materials Processing Technology Volume 166, Issue 3, 20 August 2005, Pages
411–416
Beri, N. and Kumar, A., (2011). Optimisation of electrical discharge machining process
with CuW powder metallurgy electrode using grey relation theory. International
Journal Machining and Machinability of Materials, Vol. 9, Nos. 1/2.
Beri, N., Maheshwari, S., Sharma, C. and Kumar, A., (2008). Performance Evaluation of
Powder Metallurgy Electrode in Electrical Discharge Machining of AISI D2
Steel Using Taguchi Method. International Journal of Aerospace and
Mechanical Engineering 2:3, 167 – 171.
Beri, N., Maheshwari, S., Sharma, C. and Kumar, A., (2010). Technological
Advancement in Electrical Discharge Machining with Powder Metallurgy
Processed Electrodes: Review. Material and Manufacturing Processes, 25:
1186-1197.
148
Charmilles Technologies (1991). ROBOFORM 100,200,400 Users Manual. Charmilles
Technologies Coorporation. Geneva
Che haron et al. (2008). Copper and Graphite electrode performance in electrical
discharge machining of XW42 tool steel. Journal of material processing
technology. 201: 570-573
Chow, H.M.et al., (2000). Study of added powder in kerosene for the micro-slit
machining of titanium alloy using electro-discharge machining. Journal of
Materials Processing Technology 101 (2000) 95±103
Debdulal Das et al. (2011). Sub-zero treatments of AISI D2 steel: Part I. Microstructure
and hardness. Materials Science and Engineering A 527 (2010) 2182–2193
Dewangan, S.K. (2010), Experimental Investigation of Machining Parameters for EDM
Using U-shaped Electrode of AISI P20 Tool Steel. Master Thesis Department of
Mechanical Engineering National Institute of Technology Rourkela (India)
Fleming, B. (2005). The EDM How-To-Book. Fleming Publishing. USA.
Fuller, John, E., (1996). Electrical Discharge Machining. ASM Machining Handbook,
vol. 16, pp. 557–564.
Geels, K. (2006). Metallographic and Materialographic Specimen Preparation, Light
Microscopy, Image Analysis and Hardness Testing, ASTM International
German R.M. and Heaney D.F. (2004) Advances in the Sintering of Titanium Powders,
PM 2004, Vienna, Austria.
Guitrau, E.B(1997). The EDM Handbook. Hanser Gardner Publications, Cincinnati.
149
Guu,Y.H., and Hocheng, H., (2001). Effects of workpiece rotation on machinability
during electrical discharge machining. Journal of Material and Manufacturing
Processes, 16 (1), 91–101.
Guu Y.H., Hocheng H., Chou C.Y., Deng C.S. (2003). Effect of electrical discharge
machining on surface characteristics and machining damage of AISI D2 tool
steel, Materials Science and Engineering A358: 37-43.
Guu Y.H. (2005). AFM surface imaging of AISI D2 tool steel machined by the EDM
process, Applied Surface Science 242: 245–250.
Guu,Y.H., Tsai,K.L., Chen,L.K., (2007). An experimental study on electrical discharge
machining of maganese-zinc ferrite magnetic material. Materials and
Manufacturing Processes, 22, 66 - 70.
Kumar H., and Davim J.P(2011). Role of powder in machining of Al-10%SiCp metal
matrix composites by powder mixed electric discharge machining, Journal of
Composite Materials, Sage,45, (2011), 133-151.
Khan, D.A. (2011). Effect Of Tool Polarity On The Machining Characteristics In
Electric Discharge Machining Of Silver Steel And Statistical Modelling Of The
Process. International Journal of Engineering Science and Technology (IJEST)
Kansal, H.K et al,. (2007).Effect of Silicon Powder Mixed EDM on Machining Rate of
AISI D2 Die Steel. Journal of Manufacturing Processes Vol. 9/No. 1
Kansal, H.K. et al,.(2008). Numerical simulation of powder mixed electric dischar
machining (PMEDM) using finite element method. Mathematical and
Computer Modelling 47 (2008) 1217–1237
150
Kansal, H.K. et al,. (2005). Parametric optimization of powder mixed electrical
discharge machining by response surface methodology. Journal of
Materials Processing Technology 169 (2005) 427–43.
Kansal, H.K. et al. (2006). Technology and research developments in powder
mixed electric discharge machining (PMEDM). Journal of Materials
Processing Technology 184 (2007) 32–41
Karastojkovic and Janjusevic (2003). Hardness and structure changes at surface in
Electrical Discharge Machined steel 3840. Proceedings of 3rd BMC-2003-
Ohrid, R. Macedonia
Ken, R.(2008). Sinker Electrode material Selection. EDM Magazine Today.
Ken, R.( (2011). Filtration Filtration. EDM Magazine Today.
Kiyak and Cakir (2007). Examination of machining parameter on surface roughness in
EDM tool of tool steels. Journal of Material Processing Technology, 191(200&)
141-144
Kumar ,H. and Davim,J.P. (2011). Role of Powder in the Machining Al-10%Sicpof
Metal Matrix Compositesby Powder Mixed ElectricDischarge Machining.
Journal of composite materials, Vol. 0, No. 00/2010
Klocke, F. Et al.(2004).The effects of powder suspended dielectrics on the thermal
influenced zone by electrodischarge machining with small discharge energies.
Journal of Materials Processing Technology 149 (2004) 191–197
Kung, K.Y et al (2009). Material removal rate and electrode wear ratio study on the
powder mixed electrical discharge machining of cobalt-bonded tungsten carbide.
Int J AdvManuf Technol (2009) 40:95–104
151
Kumar, A et al. (2011). Research Developments in Additives Mixed Electrical
Discharge Machining (AEDM): A State of Art Review. Materials and
Manufacturing Processes, 25: 1166–1180, 2010
Lawley, A. (1978) Powder Metallurgy Processing — New Techniques and Analyses,
Academic Press, New York, 1978
Lee, H. T et al. (2004). Relationship between electrode size and surface cracking in the
EDM machining process. Journal of Materials Science, 2004, Volume 39,
Number 23, Pages 6981-6986
Lee, S.H. and X.P. Li, (2001). Study of the effect of machining parameters on the
machining characteristics in electrical discharge machining of tungsten carbide.
J. Mater. Process. Technol., 115: 344-358.
Lonardo, P.M., and Bruzzone, A., (1999). Effect of Flushing and Electrode Material on
Die Sinking EDM. CIRP Annals - Manufacturing Technology Volume 48, Issue
1, 1999, Pages 123–126
Leonard B.L, Meek J.M. (1941). The Mechanism of the Electric Spark. The Baker and
Tailor Company, London
Liu S. (2010). Advances in Grey Systems Research. Scientific Publishing Services Pvt.
Ltd.
Ming, Q.Y and He,Y.L (1995). Powder-suspension dielectric fluid for EDM. Journal of
Materials Processing TechnologyVolume 52, Issue 1, May 1995, Pages 44–54
McGeough, J.A. (1988). Advanced Methods of Machining. Chapman and hall
LtdPublishing.London
152
Marafona, J.D. and Araujo,A., (2009). Influence of workpiece hardness on EDM
performance. Int J Mach Tool Manuf, 49, 744 - 748.
Marafona, J. and Wykes C.A., (2000). A new method of optimizing material
removalrate using EDM with copper-tungsten electrodes. Int J Mach Tools
Manuf, 40: 153 - 164.
Marafona, J. (2007). Black layer characterisation and electrode wear ratio in electrical
discharge machining (EDM). Journal of Materials Processing Technology 184:
1-3. 27-31 April
Marafona, J., (2009). Black layer affects the thermal conductivity of the surface of
copper tungsten electrode. Int J Mach Tools Manuf, 42: 482 - 488.
Marafona, J., (2009). Black layer characterization and electrode wear ratio in electrical
discharge machining (EDM). J Mat Process Tech, 184: 27 - 31.
Mohri, N.; Saito, N.; Higashi, M.A.(1991). A new process of finish machining on free
surface by EDM methods. Annals of CIRP 1991, 40 (1), 207–210.
Ojha, K. et al,.(2011).Experimental Investigation and Modeling of PMEDM Process
with Chromium Powder Suspended Dielectric. International Journal of Applied
Science and Engineering 2011. 9, 2: 65-81
Ojha, K. et al,.( (2011). Parametric Optimization of PMEDM Process using Chromium
Powder Mixed Dielectric and Triangular Shape Electrodes. Journal of Minerals
& Materials Characterization & Engineering, Vol. 10, No.11, pp.1087-1102,
2011
153
Pradhan, M.K. and Biswas, C. K. (2009 ). Modeling and Analysis of process parameters
on Surface Roughness in EDM of AISI D2 tool Steel by RSM Approach. World
Academy of Science, Engineering and Technology 57
Pandey A. and Singh S. (2010). Current research trends in variants of Electrical
Discharge Machining: A review. International Journal of Engineering Science
and Technology. Vol. 2(6), 2010, 2172-2191
Pecas, P. and Henriques,E. (2003). Influence of silicon powder-mixed dielectric on
conventional electrical discharge machining. International Journal of Machine
Tools & Manufacture 43 (2003) 1465–1471
Pecas, P. and Henriques,E. (2008). Effect of the powder concentration and dielectric
flow in the surface morphology in electrical discharge machining with powder-
mixed dielectric (PMD-EDM). Int J AdvManufTechnol (2008) 37:1120–1132
Pecas, P. and Henriques,E. (2003). Electrical discharge machining using simple and
powder-mixed dielectric: The effect of the electrode area in the surface
roughness and topography. Journal of materials processing technology 200
(2008) 250–258
Prabhu, S., and Vinayagam, B.K., (2008).Analysis of Surface Characteristics of AISI D2
Tool Steel Material Using Carbon Nano Tube. Int J Nanotech App, Volume 2,
Number 1, pp. 107 - 122.
Prabhu, S., and Vinayagam, B.K., (2011). Modeling the machining parameters of AISI
D2 tool steel material with multi wall carbon nano tube in electrical discharge
machining process using response surface methodology. International Journal of
the Physical Sciences Vol. 7(2), pp. 297 – 305
154
Ramasawmy, Blunt, L. and Rajurkar, K.P. (2005), Investigation of the relationship
between the white layer thickness and 3D surface texture parameters in the die
sinking EDM process. Precision Engineering Volume 29, Issue 4, October
2005, Pages 479–490
Rao (2009). Manufacturing Technology Vol-Ii 2E, Volume 2, Tata McGraw-Hill
Education
Rival (1995). Electrical Discharge Machining Of Titanium Alloy Using Copper
Tungsten Electrode With Sic Powder Suspension. Master Thesis UTM.
Roberts, G.A , George K., Richard L. and K (1998). Tool Steels, ASM International.
Sharma, S et al., (2010). Effect of aluminium powder addition in dielectric during
electric discharge machining of hastelloy on machining performance using
reverse polarity. International Journal of Advanced Engineering Technology
Singh, S., Maheshwaria, S., PandeyP.C. (2004). Some investigations into the electric
discharge machining of hardened tool steel using different electrode materials.
Journal of Materials Processing Technology Volume 149, Issues 1–3, 10 June
2004, Pages 272–277
Singh, S.; Maheshwari, S.; Dey, A.(2006) Electrical Discharge Machining (EDM) of
aluminium metal matrix composites using powder-suspended dielectric fluid.
Journal of Mechanical Engineering 2006, 57 (5), 271–290.
Sutherland, K. (2008). Filters and Filtration Handbook. Elsevier Limited publications
Sommer, C. (2000). Non-traditional machining handbook. First edition. Advance
Publishing. Houston
155
Sommer, C., (2009). Non-Traditional Machining Handbook: 2nd Edition. Houston:
Advance Publishing, Inc.
Sommer, C.and Sommer, S. (2005).Complete EDM Handbook, Advance Pub., 2005
Salman, O. Kayacan, M.C(2007). Evolutionary programming method for modeling the
EDM parameters for roughness. Journal of Materials Processing Technology
Volume 200, Issues 1–3, 8 May 2008, Pages 347–355
Syed K.H. and Kuppan P, (2012). Performance of electrical discharge machining using
aluminium powder suspended distilled water, Turkish Journal of Engineering
and Environmental Science, vol. 36, pp. 195-207, 2012.
Tai and Lu (2009). Improving the fatigue life of electro-discharge-machined SDK11 tool
steel via the suppression of surfacecracks. International Journal of Fatigue
Volume 31, Issue 3, March 2009, Pages 433–438
Tebni, W., Boujelbene, M., Bayraktar,E. And Salem, S.B. (2008). Parametric Approach
Model For Determining Electrical Discharge Machining (EDM) Conditions:
Effect of Cutting Parameters on The Surface Integrity. The Arabian Journal for
Science and Engineering, Volume 34, Number 1C
Tzeng, Y.F. and Lee, C.Y(2001). Effects of Powder Characteristics on Electro
discharge Machining Efficiency. Int J Adv Manuf Technol (2001) 17:586–592
Tzeng, Y.F. and Chen ,F.C(2003). Multi-objective optimisation of high-speed electrical
discharge machining process using a Taguchi fuzzy-based approach. Materials
and Design 28 (2007) 1159–1168
156
Tzeng, Y.F. (2003). Development of a flexible high-speed EDM technology with
geometrical transform optimization. Journal of materials processing technology
203 (2008) 355–364
Tzeng, Y.F. and Chen F.C., (2005). Investigation into some surface characteristics of
electrical discharge machined SKD-11 using powder-suspension dielectric oil. J
Mat Process Technol, 170: 385-391.
Tzeng, Y. F.; Chen, F. C. (2007). Multi-objective optimization of high-speed electrical
discharge machining process using a Taguchi fuzzy-based approach, Materials
and Design, Vol. 28, No. 4, 1159–1168
Uno,Y., Okada,A., and Cetin S.,(2001). Study on the Distribution of Scattered Debris
Generated by a Single Pulse Discharge in EDM Process. Design and Production
of Dies and Molds, 2001
Volk, M.W., (1996). Pump characteristics and applications, New York : Marcel Dekker
Wong, Y.S., Lim, L.C., Lee, L.C., (1995). Effect of flushing on electro-discharge
machined surfaces. Journal of Materials Processing Technology 48, 299 - 305.
Wong, Y.S., Lim, L.C.; Iqbal, R.; Tee, W.M. (1998) Near-mirror-finish phenomenon in
EDM using powder-mixed dielectric. Journal of Materials Processing
Technology 1998, 79 (1–3), 30–40.
Wu, K.L. et al.(2005). Improvement of surface finish on SKD steel using electro-
discharge machining with aluminum and surfactant added dielectric.
International Journal of Machine Tools & Manufacture 45 (2005) 1195–1201
157
Yan, B.H.; Chen, S.L. (1993). Effects of dielectric with suspended aluminum powder on
EDM. Journal of Chinese Society of Mechanical Engineering 1993, 14 (3),
307–312.
Yeo, S.H. , Tan,P.C. and W Kurnia., (2007). Effects of powder additives suspended in
dielectric on crater characteristics for micro electrical discharge machining. J.
Micromech. Microeng. 17 (2007) N91–N98
Yu, C.P.; Chen, W.C.; Chang, S.W.; Chang, C.C.(1996). Effects of the concentration
of suspended aluminum powder in dielectric fluid on EDM of carbide of
tungsten. Proceedings of the 13th Conference of Chinese Society of Mechanical
Engineers,Taiwan, 1996; 445–450.
Zhao, W.S.; Meng, Q.G.; Wang, Z.L (2002). The application of research on powder
mixed EDM in rough machining. Journal of Materials Processing Technology
2002, 129 (1–3), 30–33.