What is Electron Beam Machining (EBM) Process: Introduction, Equipment's of EBM, Working Principle, Advantages, Limitations, Applications

Introduction:-

An electron beam is generated in a beam gun. Electron beam gun provides high-velocity electrons over a really small spot size.

Electron Beam Machining (EBM) is required to be administered in a vacuum. Otherwise, the electrons would interact with the air molecules, thus they might lose their energy and cutting ability.

Thus the workpiece to be machined is found under the beam and is kept under vacuum.

The high-energy focused beam is formed to hit the workpiece with a spot size of 10-100 µm.

The K.E. of the high-velocity electrons is changed over to heat because the electrons strike the work material.

Due to high power density instant melting and vaporization start and also the "melt vaporization" front step by step progresses.

Finally, the molten material, if any at the highest of the front, is expelled from the cutting zone by the high vapor pressure at the lower part.

Major Equipment's of EBM:-

• Electron Gun: It is called the heart of EBM (Electron Beam Machining). It is used to generate electrons. It's simply a bar tube that produces lepton, speeds up them to a sufficient rate, and centers them at a little spot size. In this gun, the cathode is formed by tungsten or tantalum. This cathode filament heated to 2500 degrees that accelerates lepton emission by particle reaction. there's a terribly low vacuum within the chamber.

• Annular Bias Grid: It's the next element of EBM. It is just after the electron gun. It is an anode that is connected by the negative bias so the electrons generated by the cathode do not diverge from its path and approach to the next element. When the electrons leave this section, the speed of the electron is nearly half the speed of sunshine.

• Magnetic Lenses: After the anode, magnetic lenses are provided which shape the beam and don't allow to diverge electron or reduce the divergence of the beam. These lenses permit to pass only convergent electron, thus a highly focused beam is obtained. They also capture a low-energy electron, thus increase the standard of the beam.

• Electromagnetic lens and deflection coil: Electromagnetic lens is employed to focus the beam at a spot. They use to focus the beam at a spot on the workpiece so a high-intensity beam reaches the surface, which produces more heat and improves machining. The defecting coil doesn't allow to beam deflect and the lookout of all electrons moves serial thus form a high-intensity beam.

• Workpiece and work holding device: It can machine both metallic and non-metallic material. The workpiece is held by a reasonable apparatus which is mounted on a CNC table. This table is often moving altogether in three directions that control the form of machining.

Process parameters of EBM:- (Working Principle)

The process parameters, that directly have an effect on the machining characteristics in beam Machining, are:

• The accelerating voltage
• The beam current
• Pulse duration
• Energy per pulse
• Power per pulse
• Lens current
• Spot size
• Power density

• As has effectively been referenced in EBM the weapon is worked in beat mode.
• This is accomplished by suitable biasing the one-sided matrix found soon after the cathode. Exchanging beats are given to the predisposition lattice so on accomplish a heartbeat term of as low as 50 µs to up to 15 meters.
• Beam current is straightforwardly identified with the number of electrons radiated by the cathode or possibly among the beam. Beam current once more is often as low as 200µ amp to 1 amp.
• An increase in the energy per pulse is due to an increase in the beam circuit directly. High-energy pulses (in more than 100 J/pulse) can machine larger holes on thicker plates.
• The energy density and power density are ruled by energy per pulse length and spot size. Spot size, on the elective hand, is constrained by the level of centering accomplished by the attractive fascination focal points a superior energy thickness, i.e., for lower spot size, the material removal would be quicker although the scale of the gap would be smaller.
• The plane of focusing would get on the surface of the workpiece or simply below the surface of the workpiece. This controls the kerf form or the form of the opening.

 

Advantages of EBM:-

The advantages of Electron Beam Machining is as follows:

•  Provides very high drilling rates.

• Moreover, it can machine almost any material regardless of its mechanical properties.

• As it applies no mechanical cutting force, work holding and fixturing cost is extremely less.

• Further for an equivalent reason fragile and brittle materials also can be processed.

• The heat-affected zone in EBM is quite fewer thanks to shorter pulses.

• EBM can give openings of any shape by consolidating shaft redirection utilizing electromagnetic curls and subsequently the CNC table with high exactness.

Limitation of EBM:-

The disadvantages of Electron Beam Machining is as follows:

• The primary limitations are the high cost of capital of the equipment and necessary regular maintenance applicable for any equipment using a vacuum system.

• Moreover in EBM, there's an important quantity of non-productive pump down amount for attaining the desired vacuum. but this may be reduced to some extent victimization vacuum load locks.

• Though heat-affected zone is quite less in EBM but recasts layer formation can't be avoided.

 

Applications of EBM:-

The applications of Electron Beam Machining is as result:

• It is accustomed to turning out terribly tiny size holes from one hundred small meters to two mm.

• It is accustomed turn out holes in the diesel injection nozzle.

• Used in part industries for manufacturing rotary engine blades for supersonic engines and in nuclear reactors.