This document provides an overview of electro discharge machining (EDM). It discusses the working principle of EDM, which involves using electric sparks to erode metal to the desired shape. The key components of EDM are described, including the power generator, dielectric fluid, electrode tool, and fixture. Characteristics of EDM like its ability to machine hard materials regardless of strength are summarized. Advantages include machining complex shapes and tight tolerances, while disadvantages include slow removal rates and electrode wear. Applications of EDM mentioned are drilling micro-holes, cutting threads, and machining hardened alloys.

1. GOVERNMENT
ENGINEERING COLLEGE
PALANPUR
PRESENTED BY :-
CHAUDHARY KALPESH
(180613119003)
LODHA JAYESH .
(180613119005)
MALI DHAVAL .R.
(180613119006)
MANASIYA SAKIRALI
(180613119007)
GUIDED BY :-
PROF. N.A.PATEL
ELECTRO DISCHARGE
MACHINING
1

2. 2
CONTENT
 INTRODUCTION
 WORKING PRINCIPLE
 COMPONENTS OF EDM
 CHARACTRISTIC OF EDM
 ADVANTAGES AND DISADVANTAGES OF EDM
 APPLICATION OF EDM

3. 3
INTRODUCTION

4. • Electrical Discharge Machining is a controlled metal-removal
process that is used to remove metal by means of electric spark
erosion.
• In this process an electric spark is used as the cutting tool to cut
(erode) the work piece to produce the finished part to the desired
shape.
• Electro discharge machining process is a non-conventional and non-
contact machining operation which is used in industry for high
precision products.
4
 INTRODUCTION

5. • EDM is known for machining hard and brittle conductive materials
since it can melt any electrically conductive material regardless of
its hardness.
• EDM is mainly used to machine difficult-to-machine materials and
high strength temperature resistant alloys.
• EDM can be used to machine difficult geometries in small batches
or even on job-shop basis.
• Work material to be machined by EDM has to be electrically
conductive.
5

6. 6
 CONSTRUCTION
FIG. CONSTRUCTION OF EDM

7. 7
WORKING PROCESS

8. 8
 WORKING PROCESS
• It is metal removal process based on the principle of material
removal by electric spark between electrode tool and work piece.
• In EDM, a potential difference is applied between the tool and work
piece. Both the tool and the work material are to be conductors of
electricity.
• The tool and the work material are immersed in a dielectric medium.
Generally kerosene or deionised water is used as the dielectric
medium.

9. 9
FIG. WORKING OF EDM

10. 10
• A gap is maintained between the tool and the work piece.
Depending upon the applied potential difference and the gap
between the tool and work piece, an electric field would be
established.
• Generally the tool is connected to the negative terminal of the
generator and the work piece is connected to positive terminal.
• As the electric field is established between the tool and the job, the
free electrons on the tool are subjected to electrostatic forces. If
the work function or the bonding energy of the electrons is less,
electrons would be emitted from the tool (assuming it to be
connected to the negative terminal). Such emission of electrons
are called or termed as cold emission.

11. 11
FIG. WORKING PRINCIPLE OF EDM
• Show the above fig The “cold emitted” electrons are then
accelerated towards the job through the dielectric medium.
• As they gain velocity and energy, and start moving towards the job,
there would be collisions between the electrons and dielectric
molecules.

12. • Such collision may result in ionisation of the dielectric molecule
depending upon the work function or ionisation energy of the
dielectric molecule and the energy of the electron.
• Thus, as the electrons get accelerated, more positive ions and
electrons would get generated due to collisions.
• This cyclic process would increase the concentration of electrons
and ions in the dielectric medium between the tool and the job at
the spark gap.
• The concentration would be so high that the matter existing in that
channel could be characterised as “plasma”. The electrical
resistance of such plasma channel would be very less.
12

13. 13
FIG. WORKING ANIMATION OF EDM

14. 14
• Thus all of a sudden, a large number of electrons will flow from the
tool to the job and ions from the job to the tool.
• This is called avalanche motion of electrons. Such movement of
electrons and ions can be visually seen as a spark.
• Thus the electrical energy is dissipated as the thermal energy of the
spark.
• Generally the work piece is made positive and the tool negative.
• Hence, the electrons strike the job leading to crater formation due to
high temperature and melting and material removal. Similarly, the
positive ions impinge on the tool leading to tool wear.

15. 15
• In EDM, the generator is used to apply voltage pulses between
the tool and the job.
• A constant voltage is not applied. Only sparking is desired in
EDM rather than arcing.
• Arcing leads to localised material removal at a particular point
whereas sparks get distributed all over the tool surface leading
to uniformly distributed material removal under the tool.

16. 16
COMPONENTS
OF EDM

17. The main components in EDM:
1. Electric power generator
2. Dielectric fluid
3. Tool (Electrode)
4. Servo control unit
5. Fixture
6. Tank
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18. 18
1. POWER GENERATOR:
• In EDM Power supply converts AC into pulsed DC, used to
produce spark between cutting tool(electrode) and work piece.
• In EDM supply peak voltage ranging from 40 to 400V, and peak
discharge current ranging from 0.5 to 500 A.
• Different power generators are used in EDM and some are listed
below :
- Resistance-capacitance type (RC type)generator
- Rotary impulse type generator
- Electronic pulse generator
- Hybrid EDM generator

19. 19
Resistance-capacitance type (RC type)generator

20. 20
2. DIELECTRIC FLUID :
• The dielectric medium plays an important role in the working of
the EDM process. The dielectric is usually a low viscosity
hydrocarbon oil.
• The work piece and electrode tool are separated by the dielectric.
• During operation the dielectric medium is ruptured when the tool
and work gap is about 0.03 mm and at about 70 V.
• when the dielectric is ionized to form a column or path in the tool
and work gap so that a surge of current takes place as the spark is
produced.

21. 21
 Functions of Dielectric fluid:
1. Remain electrically non-conductive until the required breakdown
voltage is attained.
2. When once the breakdown voltage is reached it should breakdown
electrically instantly.
3. Deionize the spark gap, i.e., quench the spark rapidly after the
discharge has occurred.
4. Carry away the metal particles removed from the arc gap.
5. Act as a good cooling medium.

22. 22
 Desirable Properties of dielectric fluid:
• High electric strength for proper insulation.
• High flash and fire point to prevent fire hazards.
• Low viscosity and good wetting properties.
• Chemically neutral to prevent corrosion.
• Non-toxic in nature.
• Low decomposition rate for long life.
• Low cost.
• Good quenching properties.

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3. TOOL (ELECTRODE) :
• In EDM process the shape of the tool is transferred in the cavity cut
during machining.
• Thus, the shape and accuracy of the machined surface will depend
primarily on the shape and accuracy of the tool electrode.
• Thus the basic characteristics of electrode materials are:
- High electrical conductivity
- High thermal conductivity
- Higher density
- High melting point
• Electrodes made from brass, copper and copper alloys, graphite,
molybdenum, silver, and tungsten

24. 24
COPPER BRASS
GRAPHITE

25. 25
CHARACTERISTICS
OF EDM

26.  CHARACTERISTIC OF EDM
• The process can be used to machine any work material if it is
electrically conductive
• Material removal depends on mainly thermal properties of the work
material rather than its strength, hardness etc.
• In EDM there is a physical tool and geometry of the tool is the
positive impression of the hole or geometric feature machined.
• The tool has to be electrically conductive as well. The tool wear
once again depends on the thermal properties of the tool material.
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27. 27
• Though the local temperature rise is rather high, still due to very
small pulse on time, there is not enough time for the heat to diffuse
and thus almost no increase in bulk temperature takes place.
• Thus the heat affected zone is limited to 2 – 4 μm of the spark
crater.
• However rapid heating and cooling and local high temperature
leads to surface hardening which may be desirable in some
applications.
• Though there is a possibility of taper cut and overcut in EDM, they
can be controlled and compensated.

28. 28
ADVANTAGES AND
DISADVANTAGES
OF EDM

29. 29
• Complex shapes can be produced while it is difficult to be
machined by conventional Machining.
• Extremely hard material can be cut with tight tolerance.
• Good surface finish can be obtained.
• The part can be machined without perceivable distortion, because
there is no direct contact between tool and work piece.
• Tolerances of +/- 0.005 can be achieved.
• EDM is a no-contact and no-force process, making it well suited
for delicate or fragile parts that cannot take the stress of traditional
machining
 ADVANTAGES OF EDM

30. 30
 DISADVANTAGES OF EDM
• High power consumption.
• The removal rate of material is very slow.
• Due to electrode wear, it is difficult to reproduce sharp corners
on the work piece.
• Excessive tool wear occurs during machining.
• Only able to machine conductive materials
• More expensive process than conventional milling or turning

31. 31
APPLICATION
OF EDM

32. 32
• Drilling of micro-holes, thread cutting, helical profile milling, rotary
forming, and curved hole drilling.
• Delicate work piece like copper parts can be produced by EDM.
• Can be applied to all electrically conducting metals and alloys
irrespective of their melting points, hardness, toughness, or
brittleness.
• Other applications: deep, small-dia. holes using tungsten wire as tool,
narrow slots, cooling holes in super alloy turbine blades, and various
intricate shapes.
• EDM can be economically employed for extremely hardened work
piece.
 APPLICATION OF EDM