The document provides information about electric discharge machining (EDM). It discusses the history of EDM, which began in the 18th century with observations of erosion from electric discharge. EDM was developed in the 1940s and commercialized in the 1950s. The document describes the basic working principles of EDM, including how material is removed through electric sparks between electrodes. It also covers aspects like power generators, material removal rates, surface roughness, electrode materials and movement.

1. Electric
Discharge
Machine
(EDM)
Navrachana University
SET(Mech)
Presented By,
Apurva Solanki (12103304)
Dignesh Parmar (12103312)
Dipen Patel (12103314)
Jignesh Masani (12103330)
Vishal Dabgar (12103359)

2. History :
• In 1770 English physicists Joseph Priestly noted erosion effect of electric
discharge.
• In 1943 Two Russian scientist B.R.Lazarenko and N.I.Lazaranko found that male
and female part of electric switch has a crater from on it. And they found that if
both the electrode immersed in a dielectric erosion can be precisely controlled.
• They use this phenomena for constructive purpose and discover Electric spark
machine(EDM).
• Simultaneously American team Harold Stark , Victor Harding and Jack Beaver
developed an EDM for removing broken drills and taps form Aluminum casting .

3. History :
• In 1952, the manufacturer Charmilles created the first machine using the
spark machining process and was presented for the first time at the
European Machine Tool Exhibition in 1955.
• In 1969, Agie launched the world's 1st numerically controlled wire-cut EDM
machine.
• Seibu developed the first CNC wire EDM machine in 1972 and the first
system was manufactured in Japan.
• Recently, the machining speed has gone up by 20 times.
• This has decreased machining costs by at least 30 percent and improved
the surface finish by a factor of 1.5

4. GENERAL ASPECTS OF EDM
• Primarily used for hard metals or those that would be very difficult to machine
with traditional techniques.
• EDM typically works with materials that are electrically conductive, although
methods for machining insulating ceramics with EDM have been proposed.
• Can cut intricate contours or cavities in hardened steel without the need for heat
treatment to soften and re-harden them.
• Can also used for metal alloy such as titanium, hastelloy, kovar, and Inconel
• Also, applications of this process to shape polycrystalline diamond tools have
been reported.

5. WHAT IS EDM? INTRODUCTION
• Its a electro thermal non-traditional manufacturing process .
• Sometimes it is referred to as spark machining, spark eroding, burning, die
sinking or wire erosion
• Its a manufacturing process whereby a desired shape is obtained using
electrical discharges (sparks).
• Material is removed from the work piece by a series of rapidly recurring
current discharges between two electrodes, separated by a dielectric liquid
and subject to an electric voltage.

6. INTRODUCTION
• Two electrodes – 1) tool and other one is
2) work piece
• As distance between the two electrodes is reduced, the current intensity
becomes greater than the strength of the dielectric (at least in some
points) causing it to break.
• This allows current to flow between the two electrodes (same as a
breakdown of capacitor)

7. INTRODUCTION
• And material remove from the both sides
• To carried away debris (solid particles) flushing of dielectric is
required and new dielectric medium come between electrode gap.

8. SYSTEM OF EDM

9. WORKING PRINCIPLE
• Connect tool with -Ve and work material with +Ve polarities.
• Tool & work material immersed in a dielectric.
• Applied potential difference between two electrodes.
• Electric field generated between two electrodes.
• Free electron on tool subjected to electrostatic force. And according to
work function of electrons emitted from the tool (cold emission)

10. WORKING PRINCIPLE
• Collision take place between electron and dielectric molecules.
• Dielectric molecules ionize according to their dielectric constant &
more electrons and positive ions are generated. That leads to
increase the concentration of electron and positive ions.
• Plasma channel form between tool and work piece . Electric
resistance of this channel would be very less.

11. WORKING PRINCIPLE
• Thus large number of electrons and ions flows from tool to the job
and from job to the tool respectively. (avalanche motion of electron &
ions).
• Due to avalanche effect spark generated between tool and job.
• High energized electron and ions are impinged on job and tool and
their kinetic energy is converted into thermal energy on both the
sides. Instantaneous rise in temperature would be exceed of 10000⁰C.

12. WORKING PRINCIPLE
• Rise in temperature leads to material removal due to instant
vaporization and melting. Molten metal removed partially.
• potential difference is withdrawn.
• Plasma channel collapse ,its generates pressure and shock waves
which evacuates molten material forming crater of removed material
around the site of spark.

13. WORKING PRINCIPLE
• Thus , material removal occur in EDM due to formation of shock
waves as plasma channel collapse owing to discontinuous applied
potential difference .
• Sparks is desire in EDM process rather then a Arc . Arcing leads to
localized material removal at a particular point whereas sparks get
distributed all over the tool surface leading to uniform material
removal.
• Constant voltage is not applied between two electrodes.

14. WORKING PRINCIPAL OF EDM
• Localised spark energy very high temperature
melting and vaporization of tool and work piece material
material removal by crater forming over entire work piece surface.

15. SCHEMATIC OF EDM

16. CHARACTERISTICS OF EDM
• Work Material should be an electric conductive.
• Material removal depends on mainly thermal properties of the work
material rather than its strength, hardness etc.
• The tool has to be electrically conductive as well. The tool wear once
again depends on the thermal properties of the tool material.
• In EDM there is a physical tool and geometry of the tool is the
positive impression of the hole or geometric feature machined.

17. CHARACTERISTICS OF EDM
• Heat affected zone is limited to 2 – 4 μm of the spark crater
• Due to Rapid heating and cooling and local high temperature leads to
surface hardening which may be desirable in some applications.
• There is a possibility of taper cut and overcut in EDM, they can be
controlled and compensated.

18. MRR IN EDM
• Material remove in single spark is assume to be a hemisphere
Γ𝑠 =
2
3
𝜋𝑟3
And energy content in single spark
is , Es = V I ton this energy now distributed in followings
Heating the Dielectric
Between impinged
electron and ions
Heat the work piece

19. MRR IN EDM
So, energy available to heat work piece
Ew∝ Es
∴ Ew = K Es
Material removal in single spark is proportional to the spark energy
∴ Γ𝑠 ∝Ew∝ Es
∴ Γ𝑠 =g Es

20. MRR IN EDM
• So,
MRR =
𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 𝑟𝑒𝑚𝑜𝑣𝑎𝑙 𝑖𝑛 𝑠𝑖𝑛𝑔𝑙𝑒 𝑠𝑝𝑎𝑟𝑘
𝑐𝑦𝑐𝑙𝑒 𝑡𝑖𝑚𝑒
=
Γ𝑠
𝑡 𝑐
=
Γ𝑠
𝑡 𝑜𝑓𝑓
+𝑡𝑜𝑛
= g
𝑉 𝐼 𝑡𝑜𝑛
𝑡 𝑜𝑓𝑓
+𝑡𝑜𝑛
∴ 𝑀𝑅𝑅 = 𝑔
𝑉 𝐼
1+
𝑡 𝑜𝑓𝑓
𝑡 𝑜𝑛

21. MRR IN EDM
• This implies that ,
MRR ↑ 𝑤𝑖𝑡ℎ 𝑉 ↑ , 𝐼 ↑ 𝑎𝑛𝑑 𝑡𝑜𝑛 ↑
MRR ↓ 𝑤𝑖𝑡ℎ 𝑡𝑜𝑓𝑓 ↑
Surface finish with EDM:
Assume that spark occur side by side
Measure of surface roughness =Hm
𝑀𝑅𝑅 = 𝑔
𝑉 𝐼
1 +
𝑡 𝑜𝑓𝑓
𝑡 𝑜𝑛

22. SURFACE ROUGHNESS IN EDM
• So hm= r and Γ𝑠 =
2
3
𝜋𝑟3
hm= 𝑟 =
3
2
Γ𝑠 𝜋
1
3
since, Γ𝑠 =g Es=g V I ton
So, hm∝ V I ton
1
3
hm↑ 𝑤𝑖𝑡ℎ 𝐸𝑠 ↑
poor surface finish
And hm ↓ 𝑤𝑖𝑡ℎ 𝑉 ↓ , 𝐼 ↓ , 𝑡𝑜𝑛 ↓ good surface finish 𝑀𝑅𝑅 = 𝑔
𝑉 𝐼
1 +
𝑡 𝑜𝑓𝑓
𝑡 𝑜𝑛

23. POWER GENERATOR IN EDM
• Resistance capacitance type (RC)
• Rotary impulse generator
• Electronic pulse generator
• Hybrid EDM generator

24. POWER GENERATOR IN EDM

25. RC TYPE GENERATOR
During charging of capacitor
𝑐
𝑑𝑉
𝑑𝑡
=
𝑉0
−𝑉𝑐
𝑅 𝑐
1
𝑉0
−𝑉𝑐
=
1
𝐶𝑅 𝑐
𝑑𝑡
Integrating this equation
At t=0 , Vc=0 and at t=tc , Vc=Vc
*
𝑉 𝑐 = 𝑉0 1 − 𝑒−
𝑡 𝑐
𝐶𝑅𝑐 and charging current 𝑖 𝑐 = 𝑖0 𝑒−
𝑡
𝐶𝑅 𝑐
Where,
Ic= charging current
V0= open circuit voltage
Vc=instantaneous voltage during
charging
C=capacitance
Rc= charging resistance

26. RC TYPE GENERATOR
• During discharging capacitor
𝑖 𝑑 =
𝑉 𝑐
𝑅 𝑚
= −C
𝑑𝑉𝑐
𝑑𝑡
Integrating, at t=0 ,Vc=Vc
*
t=td , Vc=Vd
*
We got ,
𝑉𝑑
∗
= 𝑉𝑐
∗
𝑒
−
𝑡 𝑑
Rm and 𝑖 𝑑 =
𝑉 𝑐
∗
𝑅 𝑚
𝑒−
𝑡 𝑑
𝐶 𝑅𝑚
Vc = capacitor voltage during
discharging
Id = discharging current
Rm= machine resistance

27. RC TYPE GENERATOR
• For maximum power dissipation in RC type EDM
𝑉 𝑐 = 0.716 𝑉0
• Charging time/ideal time /off time
𝑡 𝑐 = −
𝑅 𝑐 𝐶
ln 1 −
𝑉 𝑐 ∗
𝑉 𝑐
• Discharging time ,
𝑡 𝑑 = −
𝑅 𝑐 𝐶
ln
𝑉 𝑑
∗
𝑉 𝑑

28. RC TYPE GENERATOR
• Frequency of operation
𝑓 =
1
𝑡 𝑐 + 𝑡𝑑
=
1
−
𝑅 𝑐 𝐶
ln 1 −
𝑉 𝑐 ∗
𝑉 𝑐
−
𝑅 𝑐 𝐶
ln
𝑉 𝑑
∗
𝑉 𝑑

29. RC TYPE GENERATOR
• Total energy discharge through a spark gap
=
0
𝑡𝑑
𝑖2
𝑑 𝑅 𝑚 𝑑𝑡
=
1
2
𝑉 𝑐
2 𝐶 𝑒−
2𝑡𝑑
𝑅 𝑚 𝐶 − 1
≅
1
2
C Vc2

30. ELECTRODE TOOL MATERIAL
• High electrical conductivity – electrons are cold emitted more easily
and there is less bulk electrical heating.
• High thermal conductivity – for the same heat load, the local
temperature rise would be less due to faster heat conducted to the
bulk of the tool and thus less tool wear.
• Higher density – for the same heat load and same tool wear by
weight there would be less volume removal or tool wear and thus less
dimensional loss or inaccuracy.

31. ELECTRODE TOOL MATERIAL
• High melting point – high melting point leads to less tool wear due to
less tool material melting for the same heat load.
• Easy manufacturability.
• Cost – cheap.

32. ELECTRODE TOOL MATERIAL
Electrode materials which are used commonly in the industry:
• Graphite (easily machinable)
• Electrolytic oxygen free copper
• Tellurium copper – 99% Cu + 0.5% tellurium
• Brass (drilling a small hole where high electrode wear is acceptable)

33. ELECTRODE MOVEMENT IN EDM
• In addition to the servo-controlled feed, the tool electrode may have
an additional rotary or orbiting motion.
• Electrode rotation helps to solve the flushing difficulty encountered
when machining small holes with EDM.
• In addition to the increase in cutting speed, the quality of the hole
produced is superior to that obtained using a stationary electrode.

34. ELECTRODE MOVEMENT IN EDM
• Electrode orbiting produces cavities having the shape of the
electrode.
• The size of the electrode and the radius of the orbit (2.54 mm
maximum) determine the size of the cavities.
• Electrode orbiting improves flushing by creating a pumping effect of
the dielectric liquid through the gap.

35. ELECTRODE WEAR IN EDM

36. ELECTRODE WEAR IN EDM
• There are Four different types of wear : Volumetric , corner , side and
End wear.
• Corner wear is most important because its determine degree of
accuracy of final cut.
• End wear — This is the reduction in the length of the electrode during
the EDM process.
End Wear = Starting Length – Final Length

37. ELECTRODE WEAR IN EDM
• 𝐸𝑛𝑑 𝑤𝑒𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 =
𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑐𝑢𝑡
𝐸𝑛𝑑 𝑤𝑒𝑎𝑟
% 𝑜𝑓 𝐸𝑛𝑑 𝑤𝑒𝑎𝑟 =
100
𝐸𝑛𝑑 𝑤𝑒𝑎𝑟
• Corner wear — Electromagnetic fields tend to concentrate at the electrode corners ,
subjecting the corners to greater wear.
• The sharper the angle more corner wear but at Blunt corners will wear less than sharp
angle corners.
• Corner wear can be minimized by choosing a small particle size electrode material that
has high strength and high density.

38. ELECTRODE WEAR IN EDM
• Corner Wear = Apparent Corner Wear + End Wear
Corner 𝑤𝑒𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 =
𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝑐𝑢𝑡
𝐸𝑛𝑑 𝑤𝑒𝑎𝑟
• 𝑉𝑜𝑙𝑢𝑚𝑒𝑡𝑟𝑖𝑐 𝑤𝑒𝑎𝑟 =
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑜𝑟𝑘𝑚𝑒𝑡𝑎𝑙 𝑟𝑒𝑚𝑜𝑣𝑒𝑑
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑑𝑒 𝑙𝑜𝑠𝑠
• Side wear — This is wear along the side walls of the electrode.

39. ELECTRODE WEAR IN EDM
• Electrode wear depends on a number of factors associated with the EDM,
like voltage, current, electrode material, and polarity.
• The melting point is the most important factor in determining the tool
wear.
• No wear EDM: No-wear EDMing is considered to be 1% or less electrode
wear.
• Parameters necessary for a no-wear condition with graphite electrodes is
positive polarity and long on-times. The off-time is set as short as possible.

40. NO WEAR EDM
• During the machining electrode will take on silvery coating due to
work metal plating on electrode.
• More plating causes electrode to grow and its form nodules that will
distort the shape of electrode.
• No wear is not leads to faster material removal rates.
• No wear conditions is only with possible with graphite electrode

41. NO WEAR FOR DIFFERENT CLASS OF GRAPHITE
approximate minimumon-time required to achieve a no-wear
condition for each class of graphite.

42. ELECTRODE WEAR IN EDM

43. ELECTRODE WEAR IN EDM
• The wear rate of the electrode tool material (Wt) and the wear ratio
(Rw) are given by Kalpakjian (1997).

44. Dielectric fluid:
• What is Dielectric fluid?
• Why it is used?
• When it is used?
• Types of Dielectric fluid
• Which Properties & Characteristics Dielectric fluids have ?

45. What is dielectric fluid…??
• A dielectric is a non-conducting substance, i.e. an insulator. Although
"dielectric" and "insulator" are generally considered synonymous,
• The dielectric fluid must be circulated under constant pressure to
flush (wash) away the metal particles and assist in the machining or
erosion process.

46. Function of dielectric fluid:
• The dielectric oil acts as a medium through which controlled electrical
discharges occur.
• The dielectric oil acts as a quenching medium to cool and solidify the
gaseous EDM debris resulting from the discharge.
• The dielectric oil acts as a medium used to carry away the solidified
EDM debris from the discharge gap to the filter system.
• The dielectric oil acts as a heat transfer medium to absorb and carry
away the heat generated by the discharges from both the electrode
and the workpiece.

47. Requirements of Dielectric Fluid:
1. The dielectic fluid should have sufficient stable dielectric strength to
provide insulation between the tool and work piece till the breakdown
voltage is reached.
2. After the spark Discharge has taken place fluid should de-ionise.
3. It should have low viscosity and a good wetting capacity to provide
effective cooling mechanism.
4. It should flush out the particles produced during the spark out of the
gap. This is the most important function of dielectric fluid . Inadequate
flushing can result in decreasing the life of the electrode and increasing
the machining time.
5. It should be chemically neutral so as not to react with the electrode , the
work piece , the worktable or the tank.

48. Continue….
6. The flash point should be high so that there are no fire hazards.
7. Neither emission of any toxic vapours nor unpleasant odours are
desirable.
8. It should maintain their properties with temperature variation,
contamination by working residuals and products of decomposition.
9. It should be economical and easily available.

49. Properties & Characteristics of Dielectric Oils:
• Viscosity
• Flash Point
• Dielectric Strength
• Pour Point
• Volatility
• Oxidation Stability
• Acid Number
• Odor
• Color

50. Viscosity
• Viscosity is the property that describes a fluids resistance to flow.
• Viscosity is commonly measured by two different units:
1. Centistokes (cST)
2. Saybolt Universal Seconds (SUS)
The system used, a lower number means a thinner (less viscous) fluid.
Generally, a thinner fluid will flush better than a thicker fluid, and for
most oils, the oil will get thinner as the oil temperature increases.

51. Flash Point
• “The flash point of a flammable liquid is the lowest temperature at which
it can form an ignitable mixture in air.”
• The Flash Point is usually reported in units of ⁰ F and is often measured by
the Cleveland Open Cup (COC) procedure.
• Flash points for common liquids are listed below:
• Gasoline -40⁰ F
• Ethanol 55⁰ F
• Kerosene 120⁰ F
• Diesel 143⁰ F
• Vegetable Oil 620⁰ F
• The flash point for commonly used EDM dielectric oils ranges from 160 ⁰ F
to 255 ⁰ F.
• Obviously for reasons of safety, the higher the flashpoint the better.

52. Flash Point
• When a liquid petroleum product is exposed to air, some of it
evaporates, causing a certain vapour/air concentration. As the
temperature of the liquid product is raised more and more
evaporates and the vapour/air ratio increases. Eventually, a
temperature is reached at which the vapour air ratio is high enough
to support momentary combustion, if a source of ignition is present.
This temperature is the Flash Point of the product.

53. Dielectric Strength:
• For a given configuration of dielectric material and electrodes, the
dielectric strength is the minimum electrical field that produces
breakdown.
• The dielectric strength is commonly measured in units of either
MV/m, or V/mil.

54. Pour Point
• The pour point of an oil is the temperature below which the oil no
longer pours freely.
• This is also sometimes called the gel point, since at temperatures
below the gel point the oil begins to gel.
• The pour point is usually stated in units of ⁰F.
• Since EDM oil is normally used at or above room temperature, one
might surmise that this property is not worthy of consideration.
• However, if your drums of dielectric fluid are stored in an unheated
area in the winter, and that fluid has a relatively high pour point, the
dielectric will gel and cannot be pumped from the drum until it is
warmed to room temperature.

55. Volatility:
• Volatility is a measure of the tendency of a dielectric fluid to vaporize.
• While most all dielectric fluids will exhibit some degree of
evaporation, the more volatile dielectric fluids will evaporate
significantly more rapidly than their less volatile cousins.
• Volatility in dielectric oils is generally related to flash point.

56. Oxidation Stability:
• Oxidation stability is a measure of the dielectric fluids tendency to
react with oxygen.
• Having greater oxidation stability means that the dielectric fluid will
resist degradation longer, retaining its clarity, initial viscosity, and give
longer service life.

57. Acid Number:
• The acid number is used to quantify the amount of acid present in a
sample of dielectric oil.
• Excessive levels of acid in a dielectric oil could lead to corrosion in the
dielectric system.
• The acid number is expressed in units of mg KOH/g, or the amount of
Sodium Hydroxide necessary to neutralize the acid present in an oil
sample.

58. Odor:
• The odor of a dielectric fluid is an important property, especially for
those that work with or near the dielectric fluid.
• there is no standard measure or specification of dielectric odor.

59. Color:
• The color of a dielectric oil can be classified by an ASTM test.
• Ideally, a dielectric fluid should be water white for maximum visibility
of the workpiece.

60. List of dielectric fluid:
• There are currently numerous choices of mineral oils formulated
specifically for EDM. They are available with a wide range of
properties and pricing.
Examples..
• Mineral Oils
• Kerosene
• deionised water
• Synthetic Oils
• Silicone Oils

61. Mineral Oils:
• Mineral oil or liquid petroleum is a by-product in the distillation of
petroleum.

62. Kerosene:
• Kerosene was one of the first popular dielectric oils. Its primary
benefit is that it has very low viscosity and flushes very well.
Unfortunately, it has many drawbacks:
• Low flash point
• High volatility
• Odor
• Skin reactions

63. • In the “old days”, there
were numerous EDM
fires and explosions
attributed to the use of
kerosene. It is no longer
used as a dielectric,
except in Third World
countries.

64. deionised water
• Tap water cannot be used as it ionises too early and thus breakdown
due to presence of salts as impurities occur.

65. Synthetic Oils
• “Synthetic oil is oil consisting of chemical compounds which were
not originally present in crude oil (petroleum), but were artificially
made (synthesized) from other compounds.”
• the cost of a synthetic EDM oil is almost double that of a mineral oil,
the life is usually double that of a mineral oil

66. Benefits of Synthetic Oils
• Longer life
• Low evaporation and volatility
• Extremely low odor
• Improved health and safety for operators

67. Silicone Oils
• In those instances where mineral and synthetic oils cannot be used,
such as the previously mentioned aerospace application in which the
solvent action of the oil is not tolerated by the wax filler material,
silicone based EDM oil is used. Silcone oil works well as an EDM
dielectric but is very expensive, limiting its use to specialty
applications.

68. Flushing in EDM

69. The adage
“The three most important things in
EDM are: Flushing, Flushing, and
Flushing”

70. What is flushing…?
• Flushing is the process of introducing clean filtered dielectric fluid into
the spark gap.
• One of the most important factors in a successful EDM operation is
the removal of the metal particles (chips) from the working gap.

71. Why it is so important…?
i. Flushing particles out of the gap between the work piece to
prevent them from forming bridges that cause short circuits.
ii. Flushing applied incorrectly can result in erratic cutting and poor
machining conditions.

72. Continue…
• while assisting in the machining process, too much fluid pressure will
remove the chips before they can assist in the cutting action, resulting
in slower metal removal, too little pressure will not remove the chips
quickly enough and may result in short-circuiting the erosion process

73. Flushing:
 Synchronized, pulsed flushing is also available on some machines.
 With this method, flushing occurs only during the non-machining time as the electrode is
retracted slightly to enlarge the gap.
 Increased electrode life has been reported with this system.
 Innovative techniques such as ultrasonic vibrations coupled with mechanical pulse EDM,
jet flushing with sweeping nozzles, and electrode pulsing are investigated by Masuzawa
(1990).

74. Flushing:
 For proper flushing conditions, Metals Handbook (1989) recommends:
1. Flushing through the tool is more preferred than side flushing.
2. Many small flushing holes are better than a few large ones.
3. Steady dielectric flow on the entire workpiece-electrode interface is desirable.
4. Dead spots created by pressure flushing, from opposite sides of the workpiece, should be
avoided.
5. A vent hole should be provided for any upwardly concave part of the tool-electrode to
prevent accumulation of explosive gases.
6. A flush box is useful if there is a hole in the cavity.

75. Flushing:
• Proper flushing depends on the volume of oil being flushed into the
gap, rather than the flushing pressure.
• High flushing pressure can also cause excessive electrode wear by
making the erode particals bounce around in the cavity.
• Generally ,the ideal flushing pressure is between 3 to 5psi.(0.2 to 0.33
bars)
• Efficient flushing requires a balance between volume and pressure.

76. Function of dielectric fluid:

77. flushing
Pressure
Through the electrode
Through the
work piece
Suction Pulse
Vertical flushing
Rotary flushing
Orbiting flushing
Jet
Flushing-types

78. 1.Pressure flushing:
pressure flushing, also called injection flushing, is the most common
and preferred method for flushing.
The great advantage of the pressure flushing is that the operator can
visually see the amount of oil that being used for flushing.
With pressure gauges, this method of flushing is simple to learn and
use

80. Pressure flushing:
1.Pressure flushing through the electrode
With pressure flushing, there is the danger of a secondary discharge .since
electricity takes the path of least resistance, secondary discharge
machining can occur as the erode particles pass between the walls of the
electrode and the work piece, secondary discharge can cause side wall
tapering. Suction flushing can prevent side wall tapering

82. Pressure flushing:
2.Pressure flushing through the work piece:
Pressure flushing can also be done by forcing the dielectric fluid
through a work piece mounted over a flushing pot.
This method eliminates the need for holes in the dielectric

84. 2.Suction flushing:
• Suction or vacuum flushing can be used to remove eroded gap
particles. suction flushing can be done through the electrode or
through the work piece.
• Suction flushing minimizes secondary discharge and wall tapering.
• Suction flushing sucks oil from the work tank, not from the clean
filtered oil as in pressure flushing.

86. 2.Suction flushing:
• For suction cutting, efficient cutting is best accomplished when the
work tank oil is clean.
• A disadvantage of suction flushing is that there is no visible oil stream
as with pressure flushing.

87. 3.Jet flushing:
• Jet or side flushing is done by tubes or flushing nozzles which direct
the dielectric fluid in to the gap
• Pulse flushing usually used with jet flushing.

89. 4.Pulse flushing :
1.Vertical flushing : Electrode moves up and down
• In vertical flushing ,the electrode moves up and down in the cavity.
• this up and down motion cause a pumping action which draws in
fresh dielectric oil and flushing out eroded particales

91. 4.Pulse flushing :
2.Rotary flushing : Electrode rotates
• In Rotary flushing the electrode rotates in the cavity .
• Rotating the electrode aids in flushing out the EDM particles from the
cavity .

93. 4.Pulse flushing :
Multiple cavities for Rotary EDMing:
• For small round electrodes , manufactures make multiple cavities in
these electrodes to aid in flushing. This is a very efficient method of
producing holes without a stud.

95. 4.Pulse flushing :
3.Orbiting flushing : The electrode orbits
• Orbiting an electrode in a cavity allows the electrode to mechanically
force the eroded particle from the cavity
• Orbiting flushing is the most efficient for cutting.
• If the orbiting is larger than the radius of the radius of the flushing holes
in the electrode, it will produce no stud

97. Flushing through hole in tool
• Result in Spike formation on work piece .
• It can be avoided by rotating tool with eccentric holes.
SPIKE

98. PROCESS PARAMETERS IN EDM

99. APPLICATIONS OF EDM
• Widely used by mold-making tool and die industry
• Also used aerospace, automobiles and electronics industry where
production quantity is relatively less.
• Coinage and die making industry for producing jewelry and badges.
• Metal disintegration machining for removing broken drills, taps bolt , studs
etc. from work piece.
• EDM can be economically employed for extremely hardened work piece.

100. • Hard and corrosion resistant surfaces, essentially needed for die making,
can be developed.
• Can be applied to all electrically conducting metals and alloys irrespective
of their melting points, hardness, toughness, or brittleness.
• Delicate work piece like copper parts can be produced by EDM.
• Small hole drilling , example: Creating cooling channels in turbine blades
made of hard alloys.

101. TYPES OF EDM
• Die sinker EDM
• Wire cut EDM
• Powder EDM

102. DIE SHINKER EDM
Main component of Die sinker EDM:
• Power system
• Dielectric system
• Electrode
• Servo system

103. WIRE EDM
Main component of wire EDM:
• Power supply
• Dielectric system
• Wire feeding system
• Positioning system

104. ADVANTAGES OF EDM
• Complex shapes that would otherwise be difficult to produce with conventional
cutting tools.
• Extremely hard material to very close tolerances.
• Very small work pieces where conventional cutting tools may damage the part
from excess cutting tool pressure.
• There is no direct contact between tool and work piece. Therefore delicate
sections and weak materials can be machined without any distortion.
• A good surface finish can be obtained.

105. DISADVANTAGES OF EDM
• MRR is slow
• For economic production, the surface finish specified should not be
too fine.
• The additional time and cost used for creating electrodes for
ram/sinker EDM.
• Reproducing sharp corners on the work piece is difficult due to
electrode wear.

106. DISADVANTAGES OF EDM
• Specific power consumption is very high.
• "Overcut" is formed.
• Excessive tool wear occurs during machining.
• Electrically non-conductive materials can be machined only with
specific set-up of the process .

107. THANK YOU