Electron Beam Machining (EBM): Definition, Principle, Diagram, Advantages

Introduction-

Want to know about Electron beam machining?

Then you landed in the right place. Here you will know the Electron beam machining process, From scratch to end.

I will cover topics like- basic definition, principles, various equipment and its construction and further working, advantages, disadvantages, application and so on.

So, stay with me while I start this knowledgeable journey with you.

So, let’s dive in.

Before I start, I want to tell you something !!

You can download this whole article in PDF and PPT format at the end of this article for your further needs and convenience.

So, Let’s get started from basic first including looking at what is an electron beam, Then we will move into the mainstream of the article-

What is Electron Beam?

The Electron Beam is a stream of negatively charged particles that are generated, accelerated, and some extent, focussed inside a device called an ” Electron Gun”.

What is Electron Beam Machining?

Electron Beam machining or EBM is a non-conventional machining process, Where the electrons are focused and concentrated on a small spot on the metal, the kinetic energy of the electrons is converted into heat energy which is sufficient to melt the workpiece, Known as Electron beam machining or EBM.

It is just similar to laser beam machining and electron beam machining is most appropriate for machines with very hard and brittle materials that cannot be machined using a conventional process.

Working principle of EBM-

EBM machining process works on the principle of the high-velocity beam of the electron is focused on the workpiece, the electrons strike on the workpiece and their kinetic energy is converted into heat energy.

This results in the removal of material from the workpiece by vaporization and melting.

Fig. Electron beam machining diagram-

electron beam machining diagram

Types of Electron Beam Machining-

There are two types of EBM machining process

  • Thermal EBM-

The Beam is used to heat the material up to the point where it is selectively vaporized.

  •  Non-Thermal EBM-

This utilizes the beam to cause a chemical reaction.

Construction of EBM-

Here are some equipment and construction of EBM machining-

  • Electron Gun
  • Magnetic lens
  • Electronic lens
  • Magnetic deflection coil
  • Optical viewing system
  • Vacuum chamber
  • Electronic system
  • Movable table

Electron Gun-

An electron gun generates and directs a controlled beam of electrons of high energy density on the workpiece to change it chemically and physically.

Magnetic Lens-

The magnetic lens is provided which shapes the beam and doesn’t allow diverging electrons or reduce the divergence of the beam.

Electromagnetic lens-

An electronic lens is used to focus the electron beam at a spot.

Magnetic deflection coil-

The Magnetic deflecting coil does not allow beam deflection and takes care of all the electron movements.

Optical viewing system-

It is a system to check whether the process is under control or not.

Vacuum chamber-

EBM process is done in the vacuum chamber to avoid any air entering probability so Electron Beam Machining is required to be carried out in the vacuum. Because air can decrease the velocity of the electron beam, hence electron beam machining requires a vacuum during the entire operation.

Electronic system-

An electronic system that controls the size and movement of the beam.

Movable table-

The workpiece is mounted on the movable table fixture that is mostly operated with CNC. The table can be move in all three directions.

Working- 

The EBM works the same as laser beam machining. Here electron beam machining working can be summarized into the following points-

  • An electron gun produces high-velocity electrons particles.
  • Then, This high-velocity electrons particle moves towards the Anode.
  • Here from the Anode, It gets concentrated and moves towards the magnetic lens.
  • Here in the magnetic lens, the convergent electrons pass through it and all divergent and low energy electrons are absorbed by it, resulting in high-quality electron beam production.
  • After passing through the magnetic lens, High-quality electrons move to the deflection coil which focuses the electron beam at the single spot point.
  • Hence High-intensity electron beam is ready to bombard on the surface of the workpiece.
  • Here kinetic energy of electrons converts into thermal energy.
  • And due to the thermal energy, the material is removed from the contact surface by melting and vaporizing.

Process Parameters-

  • Heat source: Electron gun
  • Vacuum chamber: Level of vacuum in order of 10-4 to 10-6 Torr.
  • Tungsten filament: Within the electron gun, treated as cathode, source of the stream of electrons.
  • Potential difference and current in the range of 30kV to 175kV and 50mA to 1000mA respectively.
  • The electron would travel from 50000 to 200000 km/s.

Characteristics of EBM-

  • High resolution and long depth of field that is obtained because of the short wavelength of high energy electrons.
  • Extraordinary energy
  • Workpiece material properties do not affect performance
  • Small diameter holes(0.1mm to 1.4mm) can be machined at a very fast rate.
  • No mechanical force and hence fragile, thin, low strength components can be easily machined.
  • Residual thermal stresses generated on the workpiece due to high-temperature gradient
  • Very high investment cost
  • Skilled labour required

 Advantages of EBM-

  • Fast process
  • Very high drilling rate- Upto 4000 holes/sec
  • Drills in many different configurations
  • Drills any materials, Hardness, thermal capacity, ductility, electrical conductivity or surface properties are not barriers,
  • No mechanical distortion
  • Limited thermal effects because only one pulse is required to generate each hole and pulse durations are short.
  • Computer-controlled parameters
  • High accuracy
  • Drilling parameters can easily be changed
  • No tool wear
  • Best surface finish

Disadvantages of EBM-

  • High equipment cost
  • The size of the workpiece is limited to the size of the vacuum chamber
  • Difficult to produce a perfect vacuum
  • The hole shape is affected by the depth of the workpiece because of the divergence of the beam
  • Skilled operators are needed to process
  • The process can be operated only in the vacuum chamber
  • The process results in X-ray emission which retards the production rate
  • The necessity of auxiliary backing materials
  • Frequent maintenance is required

Applications of EBM-

  • Drilling of micro holes in turbine blades, metering or flow orifice device, etc.
  • To remove small broken taps from holes
  • producing metering holes in injector nozzles of diesel engines
  • Welding of connections in electronic circuits
  • Engraving of metals and ceramics
  • Micromachining operations on thin materials like drilling, scribing, etc.
  • The multitude of holes for filters and screens in the fluid and chemical industries
  • Wire drawing dies, round or profile shaped holes on sleeve valves, rocket-fuel injectors.
  • Aerospace industries
  • Nuclear industries

 

 

Electron beam Machining is now used in many industries’ equipment. They have many special characteristics which make them most suited for specific applications.

So, that’s it for now.

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Here are some more machining processes, You would like to read about-

Plasma arc machining

Electric discharge machining

Electrochemical Machining

Water Jet Machining

Abrasive Jet Machining

Ultrasonic Machining

Difference Between Conventional and Non-Conventional Machining Processes

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