2. EDM-Principle
• A thin wire of round shape used as an electrode, which is
supplied to the work area through a pair of wheels. With the
aid of current a high power spark is produced between wire-
electrode and work piece. Due to this high amount of heat is
produced nearly to 10000 degree Celsius. This heat energy
used to melt and vaporize the work material. Then with the
supply of dielectric fluid the molten stage materials are flushed
away, likewise the machining is carried out in the work piece.
4. Specifications
Voltage = 250 V
GAP = 0.005 – 0.05 mm
Temperature = 10000 degree celcius
Spark occur = 10 – 30 micro seconds
Current density = 15 – 500 A
5. Dielectric Fluid
Petroleum Products
Paraffin
White sprit
Transformer oil
Kerosene
Mineral oil
Mixture of all
Dielectric Fluid Requirements
•Should not be toxic
•Should not be corrosive
•Should not be hazardous
•Should be circulate freely
•Should be flushed out
•Should be act as coolant
• Should be filtered before use
•Should be less cost
6. Di electric Fluid – Flushing Method
1. Pressure Flushing
2. Suction Flushing
3. Side Flushing
17. 2. R-C-L Circuit
• MRR increases with the decrease of R
Capacitor charging
time is the problem
in R-C circuit.
So to overcome this
, inductance (L) is
introduced in the
circuit
18. Rotary Pulse Generator
• R-C and R-C-L yield low MRR
• Rotary Pulse Generator over come Drawback
of above to circuits
• It give high MRR
• It give good Surface finish
• It give low tool wear
• It provide better control in all Parameters
19. Rotary Pulse Generator
• Here Capacitor is discharged through the diode during first half
cycle.
• In the next half cycle sum of voltages is given with charged
capacitor to the circuit.
• So high spark produced
• It results high MRR
Draw Back
•Poor Surface Finish
20. Controlled Pulse Generator Circuit
• All above three circuits not having any safety
incase of Short circuit in the circuit
Here in this a vacuum tube
(Transistor) is provided as an
automatic control
27. • Current Density
PROCESS PARAMETERS
Current
Density
(More
Spark)
= MRR + Surface
Roughness
Current
Density
(Less
Spark)
= MRR + Surface
Roughness
Good Surface Finish
Poor Surface Finish
31. Wire – Cut EDM (WEDM)
Travelling Wire Cut EDM (TWEDM)
0.02 – 0.03mm dia wire
Wire - Brass or Molybdenum
10 – 30 micro second sparking
15 – 500 Amp / mm2
30 - 250 V
10,000 C - Temperature
10 – 30 mm/ sec wire Feed
15 – 80 mm3 / sec MRR
Petroleum Based Hydrocarbon
Fluids – Paraffin, white Sprit ..
32. Features of WCEDM
i) Manufacturing Electrode
ii) Electrode Wear
iii) Surface Finishing – No Manual finishing needed
iv) Complicated Shapes – No need of skilled operators
v) Time Utilization – overall control is by NC Machine
vi) Straight Holes – Feed mechanism avoid taper holes
vii) Rejection – NC programmes avoid rejections
viii)Economical – for Batch production (including prototypes)
ix) Cycle Time – for die manufacturer is shorter
x) Inspection Time – very less
33. Disadvantages of WEDM
• High Capital cost
• Cutting Rate is slow
• Not suitable for large work pieces
