Electron beam machining

1. Electron Beam
Machining
DR. EMAN ELKOMY
ENG. EBRAHIM REDA

3. Made By: (G8)
Mohammed
Mahmoud Abd
Elrazzak Mostafa
(107)
Mohammed
Mahmoud Afifi
Mohammed
Elshafi’i (108)
Mohammed
Mahmoud Ali
Ahmed Elsisi
(109)
Mohammed
Mosaad
Mohammed Abd
Elazeez (110)
Mohammed
Mostafa Elsayed
Ebrahim (111)
Mohammed
Nagah Sagr Abo
Ma’aty (113)
Mohammed Nsr
Saad Ahmed
Okasha (114)
Mohammed
Yehya
Mohammed Farg
Atia (116)
Mahmoud
Essam Abd
Elstar Abdo Amer
(119)
Yousef Madaah
Elgneedy
Meshaly (149)
Yousef Naser
Fadl Abaas (150)

4. Overview of non-traditional machining processes and
their types:
1. Definition:
╺ Non-Traditional machining process is a material removal mechanism that is basically different
than those in the traditional processes, i.e. a different form of energy (other than the excessive
forces exercised by a tool, which is in physical contact with the work piece) is applied to remove
the excess material from the work surface, or to separate the workpiece into smaller parts.
╺ It’s an advanced method used to overcome the problems of Traditional Machining methods
such as tool wear, machining complex or hard surfaces, low surface finish, working on slender
or thin workpieces.

5. Characteristics of
Non-traditional
Machining process:
The hardness of tool materials can be significantly lower than that of
workpiece materials.
The material can be processed directly using energy such as electric
energy, electrochemical energy, sound energy or light energy.
Mechanical forces are not apparent during the machining and the
workpiece seldom produces mechanical and thermal deformation,
which are helpful to improve machining accuracy and surface quality of
the workpiece.
Various methods can be selectively combined into new process
methods to make the production efficiency exponentially growing and
machining precision increasing.

6. Classifications of Non-Traditional Machining:

7. ╺ There are four major classifications of Non-traditional Machining processes types depending on the nature of energy used for material removal:
1. Mechanical: Erosion of the work material by a high velocity stream of abrasives or fluids (or both)
╺ Examples: Abrasive Jet Machining (AJM) Ultrasonic Machining (USM)
2. Electro-Thermal: The thermal energy is applied to a very small portion of the work surface,
╺ causing that portion to be removed by fusion and/or vaporization of the material. The thermal energy is generated by conversion of electrical
energy.
╺ Examples: Electro-discharge machining (EDM) Laser Jet Machining (LJM)
╺ Electron Beam Machining (EBM)
3.Electrochemical: Mechanism is reverse of electroplating.
╺ Examples: Electrochemical Machining (ECM)
Electro Chemical Grinding (ECG)
Electro Jet Drilling (EJD)

8. Chemical:
Most materials (metals
particularly) are susceptible to
chemical attack by certain
acids or other etchants. In
chemical machining, chemicals
selectively remove material
from portions of the workpiece,
while other portions of the
surface are protected by a
mask.

9. Methods of Non-Traditional Machining:

10. Types of EBM Process:
╺ The following two methods are used in the EBM process.
1. Machining inside the vacuum chamber.
2. Machining outside the vacuum chamber.
╺ Construction and Working of Electron Beam
Machining:
╺ (Machining Inside the Vacuum Chamber)
╺ Construction of EBM:
╺ The schematic arrangement of Electron Beam Machining
(EBM) is shown in Fig

12. Parts:
╺ It consists of an electron gun, diaphragm, focusing lens, deflector coil, worktable, etc.
╺ To avoid collision of accelerated electrons with air molecules, a vacuum is required. So, the entire EBM setup is
╺ enclosed in a vacuum chamber, which carries a vacuum of the order 10-5 to IO-6 mm of mercury. This chamber carries a door, through
which the workpiece is placed over the table. The door is then closed and sealed.
╺ The electron gun is responsible for the emission of electrons, which consists of the following three main parts.
╺ Electron gun:
╺ It is the main part of electron beam machining. It generates the beam of an electron which is further used to remove material from
the workpiece. This electron gun contains tungsten or tantalum filament which acts as cathode.
╺ Aperture:
╺ This aperture is similar to the aperture of the camera, but the purpose of this aperture is a little different from the aperture of the
camera. This aperture is used to capture the stray electrons so that only focused and concentrated beam of electrons beam passes through
the aperture.

13. ╺ Magnetic Lens:
╺ This magnetic lens is made up of the magnet. The main function of this magnetic lens is the same as that of
an optical lens that is to concentrate the beam of electrons.
╺ Bias Grid:
╺ This bias grid is used to control the flow of electrons which is generated by an electron gun.
╺ Slotted Disc:
╺ This spotted disc is used to remove the vapor and fumes created while machining the workpiece using electron
beam machining so that this vapor and fumes do not obstruct the optical windows if the electron beam gun. This
slotted disc is synchronized with the electron beam.
╺ Anode:
╺ This anode is used to accelerate the electrons to very high velocity.
Electromagnetic Lens:
╺ The electromagnetic lens is finally used to focus the electrons beam on the workpiece.

14. ╺ The diffusion pump is used for maintaining the
vacuum within the electron beam chamber.
╺ The level of vacuum in this chamber is from 10 to the
power minus 4 to 10 to the power minus 6 torque.
╺ Optical Viewing System is used by the operator to
check whether the process is under control or not.
╺ This optical viewing system
consists of a telescope and
illumination system.

15. Working of EBM:
When the high voltage DC source is given to the
electron gun, tungsten filament wire gets heated and
the temperature raises up to 2500°C.
Due to this high temperature, electrons are emitted
from tungsten filament. These electrons are directed by
a grid cup to travel towards downwards and they are
attracted by the anode.
The electrons passing through the anode are
accelerated to achieve high velocity as half the velocity
of light (i.e., 1.6 x 10 ^8 m /s) by applying 50 to 200 kV
at the anode.

16. ╺ The high velocity of these electrons are maintained until they strike the workpiece. It becomes
possible because the electrons
╺ travel through the vacuum.
╺ This high-velocity electron beam, after leaving the anode, passes through the tungsten
diaphragm and then through the electromagnetic focusing lens.
╺ Focusing lenses are used to focus the electron beam on the desired spot of the workpiece.
╺ When the electron beam impacts on the workpiece surface, the kinetic energy of high-velocity
electrons is immediately converted into the heat energy. This high-intensity heat melts and vaporizes the
work material at the spot of beam impact.
╺ Since the power density is very high (about 6500 billion/mm ^2), it takes few microseconds to melt
and vaporize the material on impact.

17. ╺ This process is carried out in repeated pulses of short duration. The pulse frequency may range from
1 to 16,000 Hz and duration may range from 4 to 65,000 microseconds.
╺ By alternately focusing and turning off the electron beam, the cutting process can be continued as
long as it is needed.
╺ A suitable viewing device is always incorporated with the machine. So, it becomes easy for the
operator to observe the progress of the machining operation.
╺ Machining Outside the Vacuum Chamber:
╺ Since the full vacuum system is more costly, the recent development has made it possible to machine
outside the vacuum chamber. In this arrangement, the necessary vacuum is maintained within the
electron gun and the gases are removed as soon as they enter the system.

18. Process Parameters:
╺ The parameters which have a significant
influence on the beam intensity and metal
removal rate are given below:
1. Control of current.
2. Control of spot diameter.
3. Control of focal distance of the magnetic
lens.

20. Applications of EBM:
Some typical applications of the process are:
• Drill fine gas orifices, less than 0.002 mm, in space nuclear reactors, turbine blades for
supersonic aero-engines.
• To produce wire drawing dies, light-ray orifices and spinnerets to produce synthetic fibres.
• Produce metering holes in injector nozzles in diesel engines, etc.
• To scribe thin films.
• To remove small broken taps from holes.

21. 6. produce smaller size holes in various industries
like automobile, aerospace, marine
7. remove small broken taps from holes.
8. making fine gas orifices in space nuclear reactors.
9. making drawing dies and flow orifices.
10.welding small pieces of highly reactive and
refractory metals.

22. Characteristics of EBM process:

23. We hope you are happy
with this arrangement.
Thank you