The detailed study of history features and benefits of wire electric discharge machine

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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
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THE DETAILED STUDY OF HISTORY, FEATURES
BENEFITS OF WIRE ELECTRIC DISCHARGE MACHINE
Vasdev Malhotra*, Nitin Dixit**, Himani Gautam***
*Associate Professor, Mechanical Engineering Department, Mechanical Engg., YMCAUST,
Faridabad -121006, (India)
**Nitin Dixit, M.Tech Student, Mechanical Engineering Department, YMCAUST,
Faridabad, (India)
***Himani Gautam, M.Tech Student, Mechanical Engineering Department, YMCAUST,
Faridabad, (India)
ABSTRACT
Electric discharge machining is a non-conventional metal removal process used for
machining of very hard materials like ceramics, super alloysand composite matrix for manufacturing
very complex shapes which are not possible by conventional machining process. The objective of
this paper is to study the History, features and benefits of Wire cut Electric discharge machine.
Keywords: Discharge, Wire, Machining.
1. INTRODUCTION
Conventional machining processes utilize the ability of the cutting tool to stress the material
beyond the yield point to start the material removal process. This requires that the cutting tool
material is harder than the work piece material [1]. New materials which are having high strength-to-weight
ratio, heat resistance and hardness, such as nimonic alloys, alloys with alloying elements such
as tungsten, molybdenum, and columbium are difficult to machine by the traditional methods.
Machining of these materials by the conventional methods is very difficult as well as time
consuming, since the material removal rate reduces with an increase in the work material hardness
[3]. Hence, there is the, need for development of non-traditional machining processes which utilize
other methods for the material removal. As a result, these processes are termed as unconventional or
non-traditional machining methods. Non-Traditional machining processes are being used to achieve
optimum metal removal rate, better surface finish and greater dimensional correctness, with a
reduced amount of tool wear [5].

2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 5, Issue 11, November (2014), pp. 04-09 © IAEME
The Non-traditional Machining Methods are classified according to the major energy sources
employed in machining
1. Thermal Energy Methods. In these methods, the thermal energy is employed to melt and
vaporize tiny particles of work-material by concentrating the heat energy on a small area of the
workpiece. The required shape is obtained by the continued repetition of this process.
These methods include: [6]
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• Electrical discharge machining (EDM)
• Laser beam Machining (LBM)
• Plasma Arc Machining (PAM)
• Electron Beam Machining(EBM)
• Ion Beam Machining (IBM)
2. Electro - Chemical Energy Method: These methods involve electrolytic (anodic) dissolution of
the workpiece material in contact with a chemical solution.
These methods include:
• Electro-Chemical Machining (ECM)
• Electro-Chemical grinding (ECG)
• Electro-Chemical Honing (ECH)
• Electro-Chemical Deburring (ECD)
3. Chemical Energy Methods: These methods involve controlled etching of the workpiece material
in contact with a chemical solution.
• Chemical Machining Method (CHM)
4. Mechanical Energy Methods. In these methods, the material is principally removed by
mechanical erosion of the workpiece material. These methods include:
• Ultra Sonic Machining (USM)
• Abrasive Jet Machining (AJM)
• Water Jet Machining (WJM)
2. EDM (ELECTRIC DISCHARGE MACHINING)
Electric discharge machining is the one of non-traditional machining process used for
machining of the very hard materials, super alloys and composites whose machining is not possible
by conventional machining processes [3]. EDM is a controlled metal removal process that is used to
remove metals by mean of electric spark erosion so it is also known as simply spark machining. In
EDM metal removal process is performed by applying a pulsating (on/off) electric charge of high
frequency current through the electrode (act as tool) to the workpiece in the presence of dielectric
fluid [4]. This discharge occurs in a voltage gap between the electrode and workpiece. Heat from the
discharge vaporizes minute particles of workpiece material, which are washed away from the gap by
continuously flushing dielectric fluid.

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 5, Issue 11, November (2014), pp. 04-09 © IAEME
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3. HISTORY OF EDM
The erosive effect of electrical discharges was first noted by English physicist Joseph
Priestley in 1770 but history of EDM begins in 1943 when to Russian scientists, B. R. Lazarenko and
N. I. Lazarenko invent EDM first time and make possible the machining of hard materials such as
tungsten, tungsten carbide by spark erosion method. With the continuous improvements in EDM
processes, the first wire cut EDM invented in 1960 and with development of advanced techniques
and automation the first commercially available NC machine built as a wire-cut EDM machine in
1967. In 1974 wire-cut EDM machine using the CNC drawing plotter and optical line follower
techniques was produced in 1976 the first CNC EDM was introduced. [6]
4. ELECTRIC DISCHARGE MACHINING SETUP
The setup of EDM includes a power supply source, a dielectric medium, a workpiece which
is electrically conductive and an electrode which act as tool. Workpiece is connected to the positive
terminal and tool to the negative terminal of the power supply thus the workpiece become anode and
tool become cathode .This is done so because it has been observed that if both the electrodes are
made of the same material, the electrode connected to the positive terminal generally eroded at faster
rate, for this workpiece is made anode. Workpiece and electrode are separated by a small gap called
spark gap. The spark gap usually varies from .0055mm to .05mm. To maintain this predetermined
spark gap a servo control unit is used. This system correctly locates the tool in relation to the
workpiece surface, maintain constant gap throughout the operation and sense changes in the gap
conditions. When a circuit voltage of 50V to 450V is applied through dielectric medium across gap
between tool and workpiece, the electric path build up along the path of the least resistance causing
the breakdown of the dielectric fluid and formation of the spark due to the spark gap. The sparks so
caused directly impinge on the surface of the workpiece. It only takes a few microseconds to
complete the cycle and spark discharges hit the workpiece (anode) with considerable force and
velocity resulting in the development of the very high temperature of the range 10,000°C on the spot.
This temperature is high enough to vaporize and melt a very small amount of the material from the
workpiece and flushed away by dielectric fluid. The spark frequency is normally is in the range 200-
50000 Hz and this is high enough to remove a considerable amount of the material from the
workpiece.
Figure 1: shows the process method of WEDM [4]

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 5, Issue 11, November (2014), pp. 04-09 © IAEME
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4.1 Characteristics of EDM
• Voltage use – 50V to 450V
• Temperature range – 8,000°C to 10,000°C
• Spark frequency – 200 to 50000 Hz
• Spark gap - .005mm to.05mm
• Surface finish - .05μm to 12.5μm
• Tolerance – 0.005 to 0.125mm
• Material removal rate - 0.10 cm³/sec
4.2 EDM Tool
Prime requirements EDM tool Material
• It should be electrically conductive.
• It should have good machinability, thus allowing easy manufacture of complex shapes.
• It should have low erosion rate or good work to tool wear ratio.
• It should have low electrical resistance.
• It should have high melting point.
• It should have high electron emission.
4.3 The usual choices for tool (electrode) materials are
Copper,
brass,
alloys of zinc and tin,
hardened plain carbon steel,
copper tungsten,
silver tungsten,
tungsten carbide,
copper graphite, and graphite.
Servo mechanism: The gap between the tool and work has a critical importance. As the workpiece
is machined, this gap tends to increase. For optimum machining efficiency, this gap should be
maintained constant. This is done by servo- mechanism which controls the movement of the
electrode.
4.4 Dielectric Fluids
Basic Requirements of Dielectric Fluid
• low viscosity
• absence of toxic vapours
• chemical neutrality
• absence of inflaming tendency
• low cost easily available

5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 5, Issue 11, November (2014), pp. 04-09 © IAEME
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Dielectric fluids commonly used are
• quite often Kerosene based oil is used
• hydrocarbon oil
• paraffin and silicon oils
5. WIRE EDM FEATURES BENEFITS [7]
1. Exotic Materials
EDM Wire Erosion has an exceptional capability to machine exotic materials (Superalloys,
Medical grade stainless, titanium, Hastelloy, nimonics, Monel, Inconel, tungsten carbide,
aluminium alloys, copper, etc.). Work hardened metals and exceptionally ductile or brittle
materials that are difficult to machine by other methods can be shaped effectively and efficiently
by wire EDM.
2. Elimination of Stress and Distortion
Because hardened materials can be wire cut, EDM Wire Erosion eliminates the need for post-machining
heat-treating that can cause possible part distortion. Wire EDM is a completely
submerged process and imposes very little heat stress on the work piece.
3. Burr-free, Superior Edge Finish
EDM produced work pieces are accurate and burr-free, with excellent surface finish; ready
for immediate use as finished parts.
4. Intricate Contour Capability
Highly complex, contoured shapes can be produced, freeing designers to configure their
requirements, in a single piece rather than several component parts.
6. CONCLUSION
This paper shows the detailed analysis of process parameters, features and benefits of wire
electric discharge machining. EDM has emerged as the most cost effective and high precision
machining process in past years. The machining capacity to remove hard and difficult to machine
parts has made EDM as one of the most important machining processes. It also plays a significant
role in medical, optical, jewellery, automotive and aeronautic industry.
7. REFERENCES
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research to applied Research, Proceedings of the 11th International Symposium for Electro
Machining (ISEM-11), pp. 133–142.
[2] Tsai, H.C.; Yan, B.H.; Huang, F.H (2003): EDM performance of Cr/Cu based composite
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Methods and Applications, Society of Manufacturing Engineers, Dearborn, Michigan,
pp.3–4.
[4] Boothroyd, G.; Winston, A.K. (1989): Non-conventional machining processes, in
Fundamentals of Machining and Machine Tools, Marcel Dekker, Inc, New York, 491.

6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
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[5] McGeough, J.A. (1988): Electro discharge machining in Advanced Methods of Machining,
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