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
39. PRINCIPLE
Here the machining is done by usage of heat
energy.
The heat energy is focused on a particular
portion for melt & Vaporize the work material
Example :
1. Electron Beam Machining (EBM)
2. Laser Beam Machining (LBM)
3. Plasma Arc Machining (PAM)
56. History - Laser
• The laser was successfully fired on May 16, 1960. In a July 7, 1960
press conference in Manhattan,Maiman
Theodore Harold "Ted" Maiman (July 11, 1927
– May 5, 2007) was an American engineer and
physicist credited with the invention of the first
working laser Maiman's laser led to the
subsequent development of many other types
of lasers.
64. LASER BEAM MACHINING
Flash tube filled
with Xenon, argon
or krypton Gases
250 – 1000
watts power
Few
Chromium
Atoms are
placed in Ruby
rod for
absorbing
Green light
65. . Cooling of ruby rod is necessary – Because they
are less efficient in high temperature
68. MACHINING APPLICATIONS OF LASER
1. Laser in Metal Cutting
2. Laser in Drilling
3. Laser in Welding
4. Laser in Surface Treatment
5. Trimming
6. Blanking
7. Micromachining applications
71. Laser in Surface Treatment
A thin layer of cobalt alloy coating is applied on
Turbine blade for heat and Wear Resistance.
A thin Ceramic coating is applied on metal
Surface for heat and Wear Resistance.
Its also used to seal the micro cracks which are
usually present in hard – Chromium
electroplates
72. Advantages of LBM
1. All Kind of metals are machined
2. Micro holes are possible
3. Soft materials like rubber can be machined
4. No tool wear and contact with w/p
5. Automated process
6. Controlling of beam is easy
73. 1. High initial Cost
2. Operating cost is high
3. Required skilled labours
4. Rate of production is low
5. Need safety equipments
6. Life of flash lamp is low
7. The machined holes are not straight and round
Disadvantages of LBM
76. PLASMA GAS
When a gas is heated to a sufficiently high
temperature of the order of 11000 – 28000
degree Celsius, it becomes partially ionized its
known as PLASMA
PLASMA
It’s a mixture of Free electrons + Partially ionized gas
and Neutral Atoms
82. Direct Arc Plasma Torch
PILOT ARC
A Pre arc (Pilot arc) is
created b/w electrode and
nozzle
when this pre arc touches the
work piece the current flows
from work piece to electrode .
This make main arc b/w
electrode and work piece. So
now pre –Arc is switched off
83. Transferred arc process
Direct Arc Plasma Torch
• The arc is formed between the electrode(-) and the work piece(+).
• In other words, arc is transferred from the electrode to the work
piece.
• A transferred arc possesses high energy density and plasma jet
velocity. For this reason it is employed to cut and melt metals.
Besides carbon steels this process can cut stainless steel and
nonferrous metals also where oxyacetylene torch does not
succeed. Transferred arc can also be used for welding at high arc
travel speeds. A pilot arc is established between the electrode and
the nozzle. As the pilot arc touches the job main current starts
flowing between electrode and job, thus igniting the transferred
arc. The pilot arc initiating unit gets disconnected and pilot arc
extinguishes as soon as the arc between the electrode and the job
is started. The temperature of a constricted plasma arc may be of
the order of 8000 - 250000C.
85. Non-transferred arc process
In-Direct Arc Plasma Torch
• The arc is formed between the electrode(-) and the water cooled
nozzle(+).
• Arc plasma comes out of the nozzle as a flame.
• The arc is independent of the work piece and the work piece does
not form a part of the electrical circuit. Just like an arc flame (as in
atomic hydrogen welding), it can be moved from one place to
another and can be better controlled. The non transferred plasma
arc possesses comparatively less energy density as compared to a
transferred arc plasma and it is employed for welding and in
applications involving ceramics or metal plating (spraying). High
density metal coatings can be produced by this process. A non-
transferred arc is initiated by using a high frequency unit in the
circuit.
