Electron beam machining: Diagram, Principle, Working, Advantages, and Disadvantages, Applications [with Pdf]

Hello friends, Today we will discuss about the Electron beam machining or EBM.

What is Electron beam machining or EBM ?

• Electron beam machining or EBM is an non conventional machining process which uses the high velocity focused electrons beam for the machining.

• EBM is used for the machining of the brittle & hard materials which are cannot be machined by conventional machining.

• This machining process uses high velocity electrons which are about 200,000 km/s that is at 65% of speed of the light.

• EBM is suitable for the machining of the small parts.

• Read: Difference between electron beam machining and laser beam machining

Working principle:-

The Electron Beam machining works on the following principle:-

When the high velocity electrons are falls on the work-piece surface, this kinetic energy of this electrons gets converted into the heat energy which vaporizes the metal from the work-piece surface hence in such way material gets removed from the work-piece surface.

Diagram :-

Construction:-

EDM is carried out inside the vacuum chamber since if electrons comes in contact with particles in atmospheric air then electrons will loose their energy.

This machining process is consists of the following components:-

1. Power supply
2. Electron gun
   1. Tungsten filament
   2. Cathode
   3. Control grid
   4. Anode
3. Diaphragm
4. Focusing lens
5. Deflector coil
6. Work-piece Table

1) Power supply:- Power supply provides the high voltage in range of 50 kV-200 kV to electron gun for the acceleration of the electrons to the 200,000 km/s. The positive terminal of the power supply is connected to the anode & negative terminal is connected to the cathode.

2) Electron gun:- It is source of the electron beam which is consists of the Tungsten filament, Cathode, Control grid, Anode.

A) Tungsten filament:- The tungsten filament is made of the tungsten material which coverts the electrical energy into heat energy. When power starts flow across electron gun, This tungsten filament generates heat due to which heated cathode generates electron beam.

B) Cathode:- Cathode is the source of electrons. When filament gets on, Cathode emitts the electron beam. The negative terminal of the power source is connected to the cathode.

C) Control grid:- Control grid is the nickel cylinder having 15 mm length & diameter of 15 mm which is located after the cathode. It has drilled hole of 0.25 mm for the flow of electron beam through it. Control grid is negatively biased hence it controls the flow of electron beam.

D) Anode:- The anode is connected to the positive terminal of the power source. Anode accelerates the electron beam passing through the electron gun at about 2000,000 km/s which is 65% of speed of the light.

3) Tungsten Diaphragm:- Tungsten Diaphragm  removes the stray electrons from the electron beam.

4) Focusing lens:- It is electromagnetic lens which shapes the divergence of electron beam & focus it on the work-piece surface.
Focusing lens is made up of copper wire coils into the iron pole pieces.

5) Deflector coil:- It is the magnetic coil located below focusing lens which bends the electron beam to directly falls it on the desired point of work-piece surface.

6) Work-piece Table:- Work-piece table firmly holds the work-piece on it. It can moves in x , y & z axes as per requirement.

EDM working:-

1) When high voltage power supply (In range of 50 kV-200 kV) starts flow towards electron gun , Tungsten filament converts this electrical energy into the heat energy. Hence tungsten filament becomes hot around 2000°C.

2) This heated tungsten filament heats the cathode. Therefore due to heat cathode starts emitting electrons.

3) After the cathode, this electrons beam goes through the Control grid. The control grid controls the flow of electron beam.

4) The electron beam comes down through drilled hole in control grid and goes to anode. The anode accelerates this electron beam at about 200,000 km/s which is 65% of speed of the light.

5) The high velocity electron beam after anode further passes through the Tungsten diaphragm which removes the stray electrons from the high velocity electron beam.

6) After tungsten diaphragm, electron beam passes through focusing lens. The focusing lens reduces the divergent of the high velocity electron beam and focuses it on the work-piece surface.

7) The focused electron beam from focusing lens goes through deflector coil which bends the beam to fall directly to the required point on work-piece surface.

8) From focusing lens this high velocity electron beam impinges onto the work-piece surface where its kinetic energy converts into heat energy which melts & vaporizes the material from work-piece surface.

Therefore in such way machining carried out in electron Beam Machining with the help of high velocity electron beam.

EBM characteristics:-

The characteristics of the EBM are as follows:-

1. Power supply in range of 50 kV-200 kV.
2. Capacity of 4000 holes per second.
3. Velocity of electron beam about  200,000 km/sec.
4. Beam current in range of 200 Micro ampere to 1 Ampere.
5. Pulse generation by Control grid which is negatively biased with pulse duration around 50 microsecond to 15 millisecond.
6. It can produce small diameters hole of 0.1 mm to 1.4 mm.

Advantages:-

The EBM has the following advantages:-

1. Less tool wear since no physical contact between tool & work-piece.
2. Better surface finish.
3. High drilling rate which is up to 4000 hole per second.
4. Very closed dimensional tolerances can be achieved.
5. High dimensional accuracy obtained.
6. Hard & brittle material can be machined.
7. It is best suited for the machining of small parts.
8. Possible of machining of electrical conducting materials.
9. Less heat affected zone.
10. It can drilled different shape & size holes.
11. Less operating cost.

Disadvantages:-

The EBM has following disadvantages:-

1. It has less material removal rate.
2. When electron beam falls on work-piece, produces hazardous x-rays, hence high skilled operator required.
3. It has limited machining thickness of 10 mm.
4. Costly equipment’s required.
5. EDM is carried out in vacuum chamber otherwise electrons will collide with air particles and looses their energy.
6. Power consumption is high.

Electron beam machining applications:-

The EBM has following applications:-

1. In drilling multiple hole at one time.
2. In automobile industries for machining smaller parts.
3. For the drilling of non-circular holes on workpiece.
4. In drilling small size holes in aerospace industry.

FAQ:-

Read also:

• Traditional machining process or Conventional machining process 
• Laser beam machining (LBM)
• Abrasive jet machining (AJM) 
• Ultrasonic machining 
• Chemical machining