The document discusses electrical discharge machining (EDM) and compares conventional EDM to rotary EDM where the workpiece is rotated. It finds that rotary EDM increases the material removal rate compared to conventional EDM due to enhanced flushing of debris from the gap. Both material removal rate and surface roughness improve with increased rotation speed. Higher pulse current and longer pulse-on time negatively impact surface roughness by producing more molten material and a thicker recast layer, while rotation helps remove this recast layer to yield better surfaces.

1. 1
1 Contents
1 Chapter 1:............................................................. 4
1.1 Literature review: ................................................................................................... 5
1.1.1 Wire Electrical Discharge Machining ............................................................... 5
1.2 Sinker Electrical Discharge Machining:............................................................... 6
1.2.1 Small Hole EDM.................................................................................................. 6
2 Chapter 2:............................................................. 8
2.1 Introduction............................................................................................................. 9
2.2 Materials and methods:........................................................................................ 10
2.2.1 Materials and their properties for workpiece clamper and workpiece: ...... 10
2.2.2 Method: .............................................................................................................. 10
2.3 Objectives:............................................................................................................. 10
3 Chapter 3:........................................................... 11
3.1 Process parameters and performance measures: .............................................. 12
4 Chapter 4............................................................ 13
4.1 Workpiece clamper with fuel tank model in solid works .................................. 14
4.2 Manufactured workpiece clamper with fuel tank.............................................. 14
5 Chapter 5:........................................................... 15
5.1 Material removal rate........................................................................................... 16
5.2 Surface roughness................................................................................................. 17
5.3 Heat transfer by convection:................................................................................ 20
5.4 Conclusion: ............................................................................................................ 20
5.5 References.............................................................................................................. 20

2. 2
Abstract:
This work presents a novel rotary (EDM) electrical-discharge machining cutting process for a
hard-to-machine cylindrical workpiece. An experimental analysis was carried out on an AISI D2
tool steel with a copper electrode. The effects of machining parameters such as pulsed current,
pulse on-time, and workpiece rotation on material removal rate and surface roughness were
analyzed. These effects were compared with those of conventional EDM without workpiece
rotation. Experimental results indicated that the rotation enhanced the dielectric flow, thus
effectively helping flush the debris from the gap between the electrodes. In addition, the material
removal rate (MRR) increased with the rotation speed of the workpiece, whereas conventional
EDM delivers only half the MRR. Surface roughness improves with increased rotation speed, a
phenomenon that is attributed to the reduced recast layer during EDM.

3. 3
Acknowledgement:
We would like to express our gratitude to all those who gave us the opportunity to complete this
work. We would like to thank, Dr. Kashif Ishfaq, for giving guidance, design suggestions and
moral support. We are grateful to him for sharing his time and expertise. His faith in us has
always made us more confident. It had been our privilege to work under his guidance. We would
like to thank our family for their continued support throughout this work. Our parents have
always been there for us and provided the best opportunities. No one has been as motivating and
inspirational to us as our parents. Thank you for your consistent help and support
Awais Ahmed Pal (Reg No.2016-IM-21)
Hamza Mirza (Reg No.2016-IM-24)
Sandeela Naveed(Reg No.2016-IM-29)
Bilal Tahir(Reg No.2016-IM-38)
Daniyal Asif (Reg No.2016-IM-39)
M.Tahir Qadri (Reg No.2016-IM-41)
)

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1Chapter 1:

5. 5
1.1 Literature review:
The EDM machine was invited in 1943. It is used on hard metals that are electrically conductive.
These metals are impossible to machine with traditional methods such as a grinder or end mill,
so the EDM Machine is used to cut contours and cavities into the metal. Typical metals
machined on and EDM Machine include hardened tool-steel, titanium, hastalloy and carbide.
An EDM Machine uses an electrode to create electrical discharges to remove metal and make
cuts. As the electrical charge passes between the electrode and the metal being machined, cuts
are made into the metal. A continuously flowing fluid is used to flush these pieces of material
away.
ElectricalDischargeMachining Types
There are three types of electrical discharge machining, wire EDM and sinker EDM.
1.1.1 Wire Electrical Discharge Machining
The wire EDM process uses a thin metal wire fed from a spool through the workpiece to cut
plates, make punches, tool and dies. In wire electrical discharge machining, the metal and wire
cutter are submerged water, which acts as an electrical insulator.
The wire is held between upper and lower diamond guides, which are CNC-controlled and can
be programmed to cut very delicate shapes.
A typical use for wire cutting electrical discharge machining is when low residual stresses are
desired. This is because the process does not require a high cutting force for removal of
materials.
Figure 1: Wire Electrical Discharge Machining

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1.2 Sinker Electrical Discharge Machining:
Sinker EDM, also called Ram or Conventional EDM, uses an electrically charged electrode to
burn a specific shape into a metal component. It sinks shape from the electrode part into the oil
immersed work piece, not cutting all the way through the piece. The electrode discharges pulsed
electrical sparks that jump to the work piece and tear out small particles. The materials most
commonly used for the electrode are graphite, brass or copper tungsten. Graphite is used because
of its machining capabilities and wearability0, and copper for its fine finish requirements.
Through sinker EDM, parts can be formed out of even the most rigid materials and formed into
very complex shapes. However, there are also some materials that cannot be cut with sinker
EDM because they are not electrically conductive. These materials include hard and soft ferrite
materials and epoxy-rich bonded magnetic materials.
Sinker EDM is used when parts need tight tolerances or when a tight corner radius is required.
Sinker EDM is a versatile process, allowing for a variety of sized parts from those that can fit in
the palm of a hand to parts that weigh over 1,000 pounds, and everything in between. Production
dies and molds are often made through the sinker EDM process for these reasons as well.
1.2.1 Small Hole EDM
Small hole EDM is used to drill rows of holes into the leading and trailing edges of turbine
blades used in jet engines. Gas flow through these small holes allows the engines to use higher
temperatures than otherwise possible. The high-temperature, very hard, single crystal alloys
employed in these blades makes conventional machining of these holes with high aspect ratio
extremely difficult, if not impossible.
Small hole EDM is also used to create microscopic orifices for fuel system components,
spinnerets for synthetic fibers such as rayon, and other applications.
There are also stand-alone small hole drilling EDM machines with an x–y axis also known as a
super drill or hole popper that can machine blind or through holes. EDM drills bore holes with a
long brass or copper tube electrode that rotates in a chuck with a constant flow of distilled or
Figure 2: Sinker Electrical Discharge Machining

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deionized water flowing through the electrode as a flushing agent and dielectric. The electrode
tubes operate like the wire in wire-cut EDM machines, having a spark gap and wear rate. Some
small-hole drilling EDMs are able to drill through 100 mm of soft or through hardened steel in
less than 10 seconds, averaging 50% to 80% wear rate. Holes of 0.3 mm to 6.1 mm can be
achieved in this drilling operation.
Figure 3: Small Hole EDM

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2Chapter 2:

9. 9
2.1 Introduction
Electrical-discharge machining (EDM) is extensively used for high strength materials. A major
advantage of EDM is that the tool and the workpiece do not come into contact, thus eliminating
chatter and vibration problems and allowing small or thin components to be machined without
mechanical force [1,2]. As the electrical breakdown of the dielectric occurs, an electrical arc is
generated between the cathode and anode. During the period of on-time, the discharge energy
produces a very high temperature at the point of the spark on the surface of the workpiece, and
removes the material by melting and vaporization. The top surface of the workpiece resolidifies
and cools subsequently at a very high rate. The surface produced by EDM is largely influenced
by the discharge energy. This process produces the slightly dimpled surface (the increased
surface roughness), which will facilitate crack initiation on the surface. After the electrical-
discharge treatment, high tensile residual stresses often induce damage such as microcracks or
pinholes in the surface layer, which reduce the strength. The fracture strength of the material
after EDM varies significantly depending on the pulsed current applied [3–8].
During EDM, the concentration of debris in the gap increases drastically, impeding the further
removal of the materials from the gap. Fresh dielectric fluid has to enter for continuous electrical
discharge. The basic parameters of conventional EDM are the pulsed current, pulse on-time, and
pulse off-time. In rotary EDM, an additional parameter, i.e., the rotation of the electrodes, is
considered. Researchers use the techniques of applying rotation or orbital motion to the electrode
to ensure adequate flushing of the gap and to obtain better machining performance [9–10]. The
authors believe that the rotating motion of the workpiece can also rapidly remove debris from the
gap, allowing fresh dielectric to enter for effective spark discharge. This method will benefit
certain axial–symmetrical parts used in molds and dies made of difficult-to-machine materials
when the parts are electrical-discharge machined. In the present investigation, the workpiece of
AISI D2 tool steel is mounted on a rotating workpiece clamper driven at a desired speed. The
material removal rate (MRR) and surface roughness are compared with those from conventional
EDM.
Figure 4: EDM Die Sinker

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2.2 Materials and methods:
2.2.1 Materials and their properties for workpiece clamper and workpiece:
The material selected for workpiece clamper is of aluminum due to following reasons
Aluminum has high strength and light weight material due to which we got appropriate
workpiece clamper r.p.ms with low power dissipation.
The workpiece material is AISI D2 tool steel.
Table 1: Mechanical Properties of AISI D2
0.2% Offset yield strength 1532 MPa
Tensile strength 1736 MPa
Hardness (HRC) 56.57
2.2.2 Method:
We rotated the workpiece in conventional EDM so that by the rotating motion of the workpiece
debris can move rapidly from the gap, allowing fresh dielectric to enter for effective spark
discharge. This method will benefit certain axial–symmetrical parts used in molds and dies made
of difficult-to-machine materials when the parts are electrical-discharge machined.
In the present investigation, the workpiece clamper is of aluminum in which work piece is fitted.
The work piece clamper is rotated by a DC motor at a desired speed. The material removal rate
(MRR) and surface roughness are compared with those from conventional EDM.
2.3 Objectives:
The objectives of this project are following
 To manufacture a rotating workpiece clamper for EDM die sinker
 To analyze the effect of workpiece rotation on following factors
a. Material removal rate
b. Surface roughness
c. Heat transfer by convection

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3Chapter 3:

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3.1 Process parameters and performance measures:
EDM Die Sinker
Table 2: Process parameters
Dielectric Kerosene
Work material AISI D2 tool steel
Workpiece rotation 0, 1200, 2200 rpm
Tool material Copper
Pulse current (Ip) 1, 5, 10 A
Pulse on-time (τon) 20, 100, 180, 260 μsec
Pulse off-time (τoff) 20 μsec
Performance
measures
1. MRR
2. Surface
roughness
Process
parameters
Non-electricalElectrical
1. Peak current
2. Peak voltage
3. Pulse duration
4. Polarity
1. Flushing
2. Workpiece
rotation

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4Chapter 4

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4.1 Workpiece clamper with fuel tank model in solid works
4.2 Manufactured workpiece clamper with fuel tank
Figure 5: Workpiece clamper with fuel tank model in solid works
Figure 6: Manufactured workpiece clamper with fuel tank

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5Chapter 5:

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5.1 Material removal rate
The MRR was measured for both conventional and rotary EDM modes. Figure 7 shows the
relationship between the pulsed current and MRR at different workpiece rotation speeds.
According to this figure, the rotary EDM mode was associated with a higher MRR than
conventional EDM.
At a constant speed, the MRR increased with an increasing pulsed current. At a pulsed current of
1 A, workpiece rotation only slightly affected MRR. Faster workpiece rotation implied more
effective flushing of dielectric fluid and, ultimately, a higher MRR.
Figure 8 shows the effect of pulse on-time on material removal rates at different rotation speeds.
In conventional EDM, the MRR initially increased with increasing pulse on-time owing to the
higher energy input rate. A peak value was reached as the pulse on-time increased beyond a
certain value. The material removal in one spark became so large that the inter-electrode gap
condition for the next discharge was disturbed. This discharge instability induced by debris at the
gap lowered the discharge efficiency, as observed by Soni and Chakraverti [9].
For example, the eroded chips filling the gap will hinder a sound discharge. Experimental results
indicated that the maximum removal rate was 15.7 mm3min-1. The maximum MRR in
conventional EDM had an optimum pulse on-time of 180 μsec. The MRR in rotary EDM was
approximately twice as high as in conventional EDM at the same pulse on-time.
Figure 7: Effect of pulsed current on MRR at different workpiece speeds (pulse on-time 20 μsec).

17. 17
5.2 Surface roughness
EDM erodes surfaces randomly. To determine the effect of machining parameters on the surface
roughness (Ra) of tool steel, this study measured the profiles of the surfaces treated by EDM.
Figure 9 shows the effect of pulsed current on surface roughness for each of the specimen
rotation speeds.
Higher pulsed current produced a poorer surface finish, whereas a higher workpiece rotation
speed produced a lower surface roughness. On the other hand, the Ra values obtained at the pulse
current of 1 A vary less for various specimen speeds.
High pulsed current caused more frequent cracking of the dielectric fluid, causing more melt
expulsions and larger tensile residual stresses. These problems in turn resulted in poor surface
finish and serious surface damage. The surface roughness decreased with the rotation speed at
the same pulsed current.
This can be attributed to the fact that higher rotational speed provided more thorough flushing in
the gap, thus the recast layer on the machined surface was more washed off. Furthermore, the
temperature distribution during the rotary EDM was more uniform than the conventional EDM,
and the associated residual stress on the recast layer was less detrimental. Better surface
roughness was obtained through these mechanical and thermal effects.
Figure 8: Effect of pulse on-time on MRR at different workpiece speeds (pulsed current 10 A)

18. 18
To identify the effect of pulse on-time on the surface roughness, the pulse on-time was varied
from 20 to 260 μsec, while a pulsed current of 10 A was applied throughout the experiments.
Figure 10 shows the variation in the surface roughness for cases of conventional EDM and rotary
EDM. This figure reveals that the surface roughness increased linearly with increased pulse on
time. The surface roughness for rotary EDM was lower than conventional EDM for the same
pulse on-time. In fact, the roughness value of conventional EDM was almost double that of
rotary EDM at 5000 rpm
Figure 9: Effect of pulse on-time on surface roughness at different workpiece speeds (pulsed current 10 A).
Figure 10: Effect of pulse on-time on surface roughness at different workpiece speeds (pulsed current 10 A).

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A comparison of Figures 9 and 10 shows that the surface roughness constantly increased with
pulsed current as well as pulse on-time. Both quantities delivered thermal energy to the
machining location. More molten material was produced, whereas complete flushing by the
dielectric fluid became more difficult, and the resulting larger recast layer worsened the surface
finish. An excellent machined finish could be obtained by setting the machine parameters at a
low pulsed current and a small pulse on-time combined with a high workpiece rotation speed, but
this approach was more time consuming. The trends observed for conventional EDM agree with
the results reported by previous investigators [Lee et al. (15)]. The following general conclusion
can be made. In conventional EDM, insufficient flushing in the limited space results in the
stagnation of the dielectric. The debris particles become suspended in the gap and cause short
circuits, reducing machining performance. During rotary EDM, rotation of the workpiece
enhances the dielectric fluid circulation and provides a centrifugal force of flow in the gap.
Hence, the machining residue in the gap is discharged rapidly. This rapid discharge improves the
machining stability, removes more material from the specimen, and produces better surface
roughness. Figure 11 schematically shows this effect.
Figure 11:Schematic of machining in conventionaland rotary EDM. (a) Insufficient flushing
in conventional EDM. (b) Enhanced flushing in rotary EDM.

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5.3 Heat transfer by convection:
Furthermore, rotary EDM enhances heat transfer by convection, when the dielectric fluid is
carried through the gap. The temperature on the workpiece surface is more uniform compared
with the conventional EDM, hence the resulting residual thermal stress on the machined surface
is reduced. These forces produce good surface finish and minor surface damage during rotary
EDM.
5.4 Conclusion:
Workpiece rotation is effective in rotary EDM, in addition to the electrical process parameters in
conventional EDM. Experimental results indicated that debris particles in the gap inevitably
increased the discharge instability in conventional EDM. On the other hand, the centrifugal force
in rotary EDM improved gap flushing and machining efficiency. The MRR in rotary EDM was
up to twice that of conventional EDM. The value of surface roughness decreased with increasing
rotation speed. Furthermore, rotary EDM enhances heat transfer by convection, when the
dielectric fluid is carried through the gap. Hence the resulting residual thermal stress on the
machined surface is reduced. These forces produce good surface finish and minor surface
damage during rotary EDM. This work demonstrated the advantages of providing workpiece
rotation in rotary EDM. Hence, EDM of an axial–symmetrical die is improved by this technique.
5.5 References
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August, 83–98.
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3. DiBitonto, D.D.; Eubank, P.T.; Patel, M.R.; Barrufet, M.A. Theoretical models of the
electrical discharge machining process. Part I. A simple cathodc erosion model. J. Appl.
Phys. 1989, 66 (9), 4095–4103.
4. Lenz, E., Konig, W. Cracking behavior of sintered carbides during EDM. Ann. CIRP
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5. Fu, C.T.; Li, A.K. The dependence of surface damage induced by electrical discharge
machining on the fracture strength of Al2O3-Cr3C2 composites. Mater. Chem. Phys.
1994, 39, 129–135.
6. Tsutsui, T.; Tamura, T. Effect of the electro-discharge machined surface on the
mechanical properties-on the surface defects and transverse rupture strength of cemented
carbide. Bull. Jpn. Soc. Precis. Eng. 1986, 20 (1), 60–61.
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working fluid. Precis. Eng. 1986, 8 (3), 157–162.
8. Sato, T.; Mizutani, T.; Yonemachi, K.; Kawata, K. The development of an
electrodischarge machine for micro-hole boring. Precis. Eng. 1986, 8 (3), 163–168.
9. Soni, J.S.; Chakraverti, G. Machining characteristics of titanium with rotary
electrodischarge machining. Wear 1994, 171, 51–58.
10. Soni, J.S. Microanalysis of debris formed during rotary EDM of titanium alloy (Ti 6A1
4V) and die steel (T 215 Cr 12). Wear 1994, 177, 71–79.
11. Kremer, D. Effects of ultrasonic vibrations on the performance of EDM. Ann. CIRP
1989, 38, 109–112.

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12. Yan, B.H.; Chen, M.D. Effect of ultrasonic vibration on electrical discharge machining
characteristics of Ti-6A1-4V alloy. J. Jpn. Inst. Light Metals 44 (5), 281–285.
13. Jia, Z.; Ai, X.; Zhang, J. Study of mechanical pulse electric discharge machining. Precis.
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Mater. Process. Technol. 1997, 68, 83–88.
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of tool steels after EDM. Int. J. Machine Tools Manuf. 1988, 28 (4), 359–372.