2. Content
• Introduction
• Equipment/Setup
• Process
• Mechanism of material removal
• How vacuum is created?
• Process capabilities
• Advantages
• Disadvantages
• Application
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3. Introduction - EBM
• Electron beam machining (EBM) is a thermal material removal
process that utilizes a focused beam of high-velocity electrons
to perform high-speed drilling and cutting.
• Used with high power density to machine materials.
• The mechanism of material removal is primarily by melting
and rapid vaporization due to intense heating by the electrons
• Also known as “Electro-optical-thermal process”.
• Very high drilling rates are achievable.
• Can machine almost any material.
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4. Equipment/Setup
High voltage supply to
cathode
Cathode Cartridge
Bias grid
Anode
Port for vacuum
gauge
Diffusion pump
Magnetic Lens
Illuminating
system
Aperture
Telescope
Electromagnetic coils
Deflector coils
Slotted Disc
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5. Equipment/Setup
• Cathode Cartridge
• Tungsten/Tantalum
• High voltage is
applied
• 2500’C
• Thermo-ionic
emission of
electrons (Vacuum)-
thermally induced
flow of electrons
from surface.
• Negatively biased –
repel the electrons
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6. Equipment/Setup
• Bias Grid
• Highly negatively
biased
• Controls the flow of
electrons.
• To avoid the
divergence of the
electrons and send
them as a beam to
the next step
(anode)
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7. Equipment/Setup
• Anode
• Positively biased
terminal
• Due to the potential
difference b/w
cathode and anode
the electrons
accelerates.
• Velocity is approx.
half the velocity of
light – passing
through anode.
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8. Equipment/Setup
• Magnetic Lens
• Same function as
that of any lens.
• Concentrates the
beam of electrons.
• Shape the beam.
• Reduce the
divergence of the
beam.
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9. Equipment/Setup
• Aperture
• Capture the stray
electrons present
near the frame.
• (Diverged low
energy electrons.)
• Captured electrons
are then set for
obtaining a
concentrated beam
of electrons.
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11. Equipment/Setup
• Deflector coils
• Deflect the electron
beam by small
amount.
• Correct the beam in
case of not getting
proper hold-ship.
• Improve the shape
of the machined
holes.
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13. Equipment/Setup
• Slotted Disc
• To avoid obstruction
of vapor of metal
into the optical
window of EBM.
• Allow Electron beam
to pass but not the
vapors/metal fumes
to pass through it.
• Synchronized with
the pulsed beam.
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14. How vacuum is created ?
DIFFUSION PUMP
Heater
Backing
Pump
Boiler
Nozzle
Cooling
Coils
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15. How vacuum is created ?
Main element for creating the vacuum is DIFFUSION PUMP.
The oil diffusion pump is operated with an oil of low vapor pressure.
Its purpose is to achieve higher vacuum.
Diffusion pump is essentially an oil heater. As the oil is heated the oil
vapour rushes upward where gradually converging structure.
The nozzles change the direction of motion of the oil vapour and the
oil vapour starts moving downward at a high velocity as jet.
Such high velocity jets of oil vapour entrain any air molecules present
within the gun. (Due to the high momentum of oil jet air is removed)
This oil is evacuated by a rotary pump via the backing line.
Level of vacuum – 10-4 to 10-6 Torr
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16. Mechanism of material
removal
• As high voltage is applied across the Cathode filament ,
thermo-ionic emission of electrons takes place.
• These Thermo-ionic electrons are replied by the cathode and
attracted by anode through the bias grid, electrons are
accelerated to the half of the velocity of the light.
• These electron/beam of electron is shaped and focused with
the help of series of magnetic and electromagnetic lenses.
• Finally the electron beam impinges the workpiece.
• Upon impingement the kinetic energy of the electron is
absorbed by the workpiece which will result into heating,
melting and vaporization – drilling.
• Spot size – 10 to 100 microns – high energy density
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17. Mechanism of material removal
Localized heating by
focused electron beam
Gradual formation of hole
Auxiliary
workpiece
Auxiliary
workpiece
W/P W/P
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18. Mechanism of material removal
Penetration till the
auxiliary support
Removal due to high
vapour pressure
Auxiliary
workpiece
W/P
Auxiliary
workpiece
W/P
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19. Advantages
EBM provides very high drilling rates when small holes
with large aspect ratio are to be drilled.
Moreover it can machine almost any material
irrespective of their mechanical properties. As it applies
no mechanical cutting force, work holding and fixturing
cost is very less.
Further for the same reason fragile and brittle materials
can also be processed. The heat affected zone in EBM is
rather less due to shorter pulses.
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20. Disadvantages
The primary limitations are the high capital cost
of the equipment and necessary regular
maintenance applicable for any equipment using
vacuum system.
Moreover in EBM there is significant amount of
non-productive pump down period for attaining
desired vacuum.
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