This document reviews recent advancements in die-sinking electrical discharge machining (EDM). It discusses ultrasonic-assisted EDM with tool or workpiece vibration, which can increase material removal rate and surface quality by facilitating debris removal via compression and rarefaction waves. Applying a magnetic field during EDM is also shown to enhance ionization and plasma formation, increasing material removal rate and electrode wear rate. Varying the tool geometry, such as using multiple eccentric holes or changing the tool material to brass, can further improve process outputs. Finally, powder-mixed EDM is reviewed and found to yield higher material removal rates and surface finishes compared to conventional EDM when using titanium nano-powder in the dielectric at optimal

1. A REVIEW OF ADVANCEMENTS IN DIE-SINKING
ELECTRICAL DISCHARGE MACHINE (EDM)
DEPARTMENT OF MECHANICAL ENGINEERING 1
11-Apr-19

2. CONTENTS
1. Introduction
2. Typical Electrical Discharge Machine (EDM)
3. Ultrasonic Assisted Electrical Discharge Machine (UAEDM) with
Tool Vibration
4. UAEDM with Workpiece Vibration
5. Effects of Applying Magnetic Field
6. Effect of Changing Geometry of the Tool
7. Powder Mixed Electrical Discharge Machine (PMEDM)
8. Conclusion
9. References
2

3. 3INTRODUCTION
Joseph Priestly
 Erosive effect of electrical discharge 1st noted by
Joseph Priestly (1770)
 Russian scientists, B. R. Lazarenko and N. I.
Lazarenko invented EDM (1943)
❑ Tried to prevent erosion of W electrical contact due to
sparking (failed)
❑ R-C type machine
 American team, Harold Stark, Victor Harding, and
Jack Beaver, developed an EDM machine (1943)
❖ To remove broken drills & taps of Al castings (failed)
❖ Automatic spark repetition & fluid replacement
❖ Produce 60 sparks/sec

4. INTRODUCTION
 EDM is an unconventional non contact machining process using electrical
and thermal energy
 Major advantage is mechanical stresses, chatters and vibrations are not
present in EDM
 Major disadvantages are
1. Slow material removal rate (MRR)
2. High electrode wear rate (EWR)
3. High surface roughness (SR) and subsurface damage
4. Thin and brittle heat affected zone (HAZ)
4

5. 5ELECTRICAL DISCHARGE MACHINE
Fig:1 Schematic diagram of electro-discharge machine [1]
1. Pulse generator
2. Workpiece
3. Fixture
4. Dielectric fluid
5. Pump
6. Filter
7. Tool holder
8. Spark
9. Tool

6. 6

7. USAEDM 7
US Vibration
Tool Workpiece Dielectric
 It boost the performance of EDM
 Facilitate easier ejection of debris from gaps

8. 8USAEDM WITH TOOL VIBRATION
Fig:2 Schematic set-up for experiments [2]

9. 9Conditions & Variables Description
Max amplitude of US vibration 5 μm
Frequency of US vibration 25 KHz
Gap average voltage 40 V
Workpiece Cemented tungsten carbide Φ10
mm and 6.5 mm thickness
Tool Copper, Φ24 mm O.D.& Φ14 mm
I.D. Cup
with bottom thickness of 2.5 mm
Dielectric Kerosene 85% & transformer oil
15%
Pulse durations 1, 5, 10, 20 and 30 μs
Pulse off time 10 μs
Output power of transducer 200 W
Table 1: Experimental conditions and process variables [2]

10. 10
Fig:3 Effect of tool vibration on MRR versus pulse-on time
for US/EDM and pure EDM [2]
As Ti increases tool vibrates
for a long duration
Compressive & rarefaction
wave front will arise
Rarefaction state suck debris
particle & compression state
expel it from gaps, like a PUMP
Short circuit due to debris
decreases
MRR increases

11. 11
Discharge current(I) increases
Discharge energy (VI) increases
in addition with vibration energy
Melting & evaporation increases
MRR increases
Fig:4 Effect of tool vibration on MRR versus pulse current for
US/EDM and pure EDM [2]

12. 12
Fig:5 Effect of tool vibration on TWR versus pulse current for
US/EDM and pure EDM [2]
As tool vibration
progresses
Cavitation near the
tool increases
Cavitation bubbles
collapse near the
surface of tool
This drives high
speed jets of liquid
on to electrode
surface
Generation of
shock waves
TWR increases

13. 13
Fig:6 Effect of tool vibration on Ra versus pulse current for
US/EDM and pure EDM [2]
As tool vibration
progresses
Molten metal being
ejected by every discharge
Craters become deeper &
wider
Ra value increases

14. 14USAEDM WITH WORKPIECE VIBRATION
Fig:7 a) Schematic of EDM
setup, b) magnetic field
poles and ultrasonic table, c)
schematic of magnetic field,
d) dry EDM process [3]

15. 15
Fig:8 Effect of power of US table on process characteristics [3]
Compression &
rarefaction
waves
Cavitation

16. 16Effect of cavitation on MRR
When
cavitation
bubble
collapses
Gas will be
compressed
& heated
abruptly
Short
period
localized
hot spots
will arise
T=5000K
P=1000atm
Dielectric
medium
dissociates
Ionization
of m/c ing
gap
increases
MRR
increases

17. 17
Fig:9 Effect of power of US table on surface
roughness [3]
When US power
increases
Waves pump debris from
m/c-ing gap
SR decreases
Further increase in US
power increase ionization
SR increases

18. 18
Fig:10 Effect of magnetic field on process characteristics [3]
APPLYING MAGNETIC FIELD
When magnetic field applied
Ions disengage from their atomic core
Ionization enhances
Plasma formation accelerates
Ignition delay time decreases &
MRR, EWR increases

19. 19
Fig:11 Effect of magnetic field on surface roughness [3]
When magnetic field applied
Debris are taken away from m/c-
ing gap
Surface quality increases
SR decreases
Condition Input parameters
I
(A)
Ton
(μs)
Toff
(μs)
N
(rpm)
P (bar)
1 30 800 100 500 2
2 15 200 100 200 2
Table 2: Experimental conditions [3]

20. 20
Fig:12 Effects of tool geometry and
material on a) MRR [3]
Fig:10 Tools
with various
geometries
a) two
eccentric
holes,
b) one
eccentric hole
CHANGING TOOL GEOMETRY IN DRY EDM
Specific
resistance of
Brass>copper
Brass has high
spark intensity
MRR
increases
When no.
of holes
increases
Air flow
rate
increases
Better
flushing of
debris
MRR
increases

21. 21
Fig:13 Effects of tool geometry and
material on b) EWR, c) SR [3]
(MP)Brass < (MP)Cu »»» (EWR)Brass > (EWR)Cu
As no. of holes
increases
Spark
producing area
decreases
Melting; EWR
increases
Better flushing
of debris cause
SR to decrease

22. 22POWDER MIXED EDM (PMEDM)
Fig:14 The powder-mixed EDM designed circulation system [4]
Parameters Value
Powder
concentration
(g/l)
~2
Voltage (V) 120
Machining time
(min)
10
Electrode (mm) Cu, Φ10
Workpiece Die steel D2
Dielectric Hydrocarbon oil
Powder material
& size (nm)
Titanium, 40-60
Table 3: Experimental conditions [4]

23. 23
Fig:15 Material removal rate (MRR) for pure dielectric and Ti nano-powder dielectric. [4]

24. 24
At const Ton,
when I increases
Spark energy
(Wt) increases
Wt ∝ VITon
MRR increases
At const I,
When Ton
increases
Spark
frequency (F)
decreases,
F=
1000
𝑇 𝑜𝑛+𝑇𝑜𝑓𝑓
Wt decreases
MRR
decreases

25. 25
Fig:16 Discharge gap in (a) pure dielectric and (b) Ti nano-powder dielectric [4]

26.  The MRR, EWR and SR values are higher for USAEDM with tool
vibration compared with pure EDM
 Compression rarefaction waves and cavitation effects have got
significant role in USAEDM
 Magnetic field has positive effect on MRR and EWR
 PMEDM has good results on MRR and SR values at particular range of
pulse on time values
CONCLUSION 26

27. REFERENCES
1. H Marashi et.al. “Techniques to Improve EDM Capabilities : A Review” by
University of Malaya, KualaLumpur, Malaysia (2016)
2. Shabgard MR, Sadizadeh B, Kakoulvand H. “The effect of ultrasonic vibration
of work piece in electrical discharge machining of AISIH13 tool steel.” In:
Proceedings of the 52nd World Academy of Science, Engineering and
Technology.
3. Reza Teimouri, Hamid Baseri “Experimental study of rotary magnetic field-
assisted dry EDM with ultrasonic vibration of workpiece.” Int J Adv Manuf
Technol (2013) 67:1371–1384
4. Houriyeh Marashi et.al. “Employing Ti nano-powder dielectric to enhance`
surfacecharacteristics in electrical discharge machining of AISI D2 steel“,
Applied Surface Science 357 (2015) 892–907
27

28. THANK YOU
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