Two Russian scientists invented electrical discharge machining in 1943 while trying to prevent erosion of tungsten contacts from sparking. EDM works by using electrical sparks to erode metal by melting and vaporizing small amounts of material. Key components of EDM include electrodes, dielectric fluid, and a power supply that provides pulsed voltage. EDM can machine hard metals and complex shapes and is especially useful for dies and molds due to its ability to machine without affecting heat treatment of the workpiece material.

1. Presented by :
SAMEER AMALE
ENROLLMENT ID:
13MT07IND013

2. HISTORY:
Two Russian scientists, B. R. Lazarenko and N. I.
Lazarenko, were tasked in 1943 to investigate ways of
preventing the erosion of tungsten electrical contacts due to
sparking.
 They failed in this task but found that the erosion was
more precisely controlled if the electrodes were immersed in
a dielectric fluid.
This led them to invent an EDM machine used for working
difficult to machine materials such as tungsten

3. Introduction :
Electric discharge machining is a manufacturing process
whereby a desired shape is obtained using electrical
discharges
 Used for hard materials or materials which are hard for
machining
 EDM typically works with materials that are electrically
conductive
EDM can cut intricate contours or cavities in pre-
hardened steel without the need for heat treatment

4. Electrical discharge machining (EDM)
Principle
Principle
 Based on erosion of metals by spark discharges.
 EDM system consist of a tool (electrode) and work piece,
connected to a pulsating (On/Off)dc power supply and
placed in a dielectric fluid
 when potential difference between tool and work piece is
high, a transient spark discharges through the fluid,
removing a small amount of metal from the work piece
surface.

5. Schematic illustration of the electrical-discharge machining process. This
is one of the most widely used machining processes, particularly for die-
sinking operations.
Electrical discharge machining
(EDM)

6. COMPONENT OF EDM:
Electrodes –
 Electrode material should be such that it
would not undergo much tool wear when it
is impinged by positive ions.
 Basic characteristics of electrode materials
are:
High electrical conductivity
High thermal conductivity
 usually made of graphite, copper , tungsten

7. Dielectric fluid–
Mineral oils, kerosene, distilled and de ionized water etc.
Role of the dielectric fluid
1. acts as a insulator until the potential is sufficiently high.
2. acts as a flushing medium and carries away the waste.
3. also acts as a cooling medium.

8. Electric power supply:
 The work piece and tool are electrically connected to a DC
power supply.
 The current density in the discharge of the channel is of the
order of 10000 A/cm2 and power density is nearly 500
MW/cm2.
 Servo Mechanism is used maintain a gap, known as SPARK
GAP in the range, from 0.005 mm to 0.05 mm is maintained
between the work piece and the tool .
 Dielectric slurry is forced through this gap at a pressure of 2
kgf/cm2 or lesser

9.  When using RC generators, the voltage pulses, shown in Fig. are
responsible for material removal.
 A series of voltage pulses (Fig.) of magnitude about 20 to 120 V and
frequency on the order of 5 kHz is applied between the two electrodes.

10. EDM – Power & Control Circuits

11. EDM – Working Principle:
 Tool is connected to the negative terminal (cathode)
 workpiece is connected to positive terminal (anode)
 Application of Potential difference (50 to 450 V)
 Establishment of electric field due potential difference and gap
 Thus free electrons on the tool are subjected to electrostatic forces.
 Cold emission and acceleration of the electron towards job through
the dielectric medium
 collisions between the electrons and dielectric molecules
 Such collision may result in ionization of the dielectric
molecule.

13. Continued...
increase the concentration of electrons and ions resulting in channel
called as plasma.
The electrical resistance of such plasma channel would be very less
 a large number of electrons will flow from tool to job and ions from job
to tool resulting in electrical spark
 Electrical energy is dissipated as the thermal energy of the spark.
 extreme instantaneous confined rise in temperature which would be
in excess of 10,000oC.
 Material removal occurs due to instant vaporization of the material as
well as due to melting.

14.  The melting point is the most important factor in determining the
tool wear.
 Electrode wear ratios are expressed as end wear, side wear,
corner wear, and volume wear.
 “No wear EDM” - when the electrode-to-workpiece wear ratio is 1
% or less.
 Electrode wear depends on a number of factors associated with
the EDM, like voltage, current, electrode material, and polarity.
 The change in shape of the tool electrode due to the electrode
wear causes defects in the workpiece shape.

16.  In EDM, the metal is removed from both workpiece and tool electrode.
 MRR depends not only on the workpiece material but on the material
of the tool electrode and the machining variables such as pulse
conditions, electrode polarity, and the machining medium.
 Typical removal rates range from 0.1 to 400 mm3 /min.
 MRR or volumetric removal rate (VRR), in mm3/min, was described by
Kalpakjian (1997):
where I - EDM current (A)
Tw - Melting point of the workpiece (°C).

17. Effect of pulse current (energy) on MRR & surface
roughness.

18. Effect of pulse on-time (energy) on MRR & surface
roughness.

19. Introduction:
It is a unique technology introduced late in 60’s.
Although the process is slow and relatively limited compared to
today’s standard its use spread quickly due its accuracy and
effectiveness
It is capable of producing complex shapes such as taper ,
involute, Parabolas, ellipses.
WIRE EDM

20. Wire EDM
 This process is similar to contour cutting with a band
saw.
 a slow moving wire travels along a prescribed path,
cutting the work piece with discharge sparks.
 wire should have sufficient tensile strength and fracture
toughness.
 wire is made of brass, copper or tungsten. (about
0.25mm in diameter).

21. Schematic illustration of the wire EDM
process.

22. Main Component of Wire EDM:
Power supply
 Dielectric Medium
Wire Feeding System
Positioning System

23. Products Manufactured Using EDM

24. ADVANTAGES :
Metal removal does not depend upon mechanical
properties of workpiece material
Complex shapes can be produced
Holes of size less than 0.1 mm also can be produced
EDM gives highest metal removal rate among all
unconventional machining method
 Surface finish produced will be better

25. LIMITATIONS:
 Only electrically conductive materials can be machined
 Hardening effect takes place
 Perfect square corners cant be produced with EDM
Power consumption is very high

26. Applications :
Drilling of micro-holes,
Delicate work piece like copper parts can be produced by EDM
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.
Hard and corrosion resistant surfaces, essentially needed for die
making, can be developed.

27. REFERENCE:
International journal of Machine tool and Manufacture
Electrical discharge machining by Elman c. Jameson
Google .com
wikipedia.org/wiki/Electrical_discharge_machining