Laser Beam Machining – Principle, Working, Advantages and Disadvantages

Laser Beam Machining is a thermal machining process which uses laser beam to produce heat and remove material from workpiece.

In this machining, metal is removed from workpiece by melting and vapourizing of metal particles in a controlled from its surface using heat from laser.
Laser Beam machining is widely used in cutting sheet and drilling holes.
It is a non-conventional machining process in which tools are used. Laser machining is mostly used in cutting and drilling operations. Both metallic and non-metallic workpiece can be machined using this machining process.

Working Principle:-

The full form of LASER is Light Amplification by Stimulated Emission of Radiation.
When electrons of an atom are provided an external energy source, they absorbs energy from the external source. By absorbing the energy these electrons jump from their original energy level to higher energy level.
But this is not stable condition of atoms, so this electron emits absorbed energy in the form of photons of light and come back to its original state. This emission of photons by electrons is called spontaneous emission.
The atom will emit double energy if it is already at higher energy level and it again absorbs energy.
The energy emitted by atom will have same frequency and wavelengths as that of stimulating source. This is the fundamental principle on which laser works.
When a laser material is placed under some energy source, it absrobs energy to some extent and release it when it reaches its absorbing limit. Thus the highly amplified light produced is called laser.

Laser machining process works on the basic principle of laser. In this machining process, a laser beam is used which is a monochromatic high intense light which can cut any metal and non-metal.

Laser machining can be used to cut and remove material from even the hardest material present which is damond.

Equipments and Main Parts :-

These are the main equipments that used in laser beam machining:-

1) Power Supply :-
The power supply is used in laser beam machining to provide energy for the excitation
of electron from lower energy level to higher energy level.

2) Laser Discharge Tube :-
Laser material is filled in laser discharge tube. The excitation of electron and coming
back to its original state takes place inside this laser discharge tube.
One side of discharge tube is partially transparent and other side is 100% reflected.
It is situated between the xenon lamps.

3) Laser Material:
There are many kinds of  laser materials available but in laser machining mostly CO2 and nd:YAG is used.  Carbon dioxide is a laser material which emits light in infrared region. Carbon dioxide can provide power upto 25 KW power in continuous wave mode. bd:YAG is a solid state laser which can deliver light through optical fiber. In pulse mode it can produce upto 50 kW power and in continuous mode it can produce power upto 1 KW.
Focusing lens :Focusing lens is used to focus the light at the workpiece. It is a convex lens.

Working of laser beam machining:-

These are the steps invoved in laser beam machining:-

At first laser material CO2 or other laser material is filled into discharge tube.
After that the power supply is switched on which is used to light up the flash lamp. The light from flash lamp is used to excite the electronsof atom.
Then the atoms of laser material absorbs energy from the light energy produced by flash lamp. Due to absorbtion of energy, the electron of atom jump from lower energy level to higher energy level. But this is unstable condition of atom.

When the atom reaches its absorbtion limit, it starts emitting energy contnuously. This energy is emitted in the form of highly amplified same frequency and same wavelength coherent light.

This laser light released by atom is collected in the convex lens and is directed towards the workpiece.

As the laser falls on workpiece, it starts the machining process by melting or vapourising material from contact surface of workpiece.

Advantages:

1 It can be used to cut aby material.
2) No tool cost because no physicla tool is required and hence no cost for mantenance and replacement of tools.
3) No delamination is caused as there is no physical contact with the workpiece.
4) It can be easily automated and is very flexible.
5) Complex shapes of different sizes can be machined as laser can be moved in any path.
6) It gives very good surface finish.
7) Micro holes can be drilled in workpiece with high accuracy.

Disadvantages:-

1) Very high capital and maintenance cost.
2) It cannot be used to produce blind hole.
3) It can lead to safety hazards.

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