Laser Beam Machining (LBM) - Principle, Construction and Working

The emergence of advanced engineering materials, stringent design requirements, intricate shape and unusual size of the workpiece restrict the use of conventional machining methods. Hence it was realized to develop some nonconventional machining methods known as advanced machining processes. Nowadays many advanced machining processes are being used in the industry such as Electro Discharge Machining, Laser Beam Machining, Electron Beam Machining, Ion Beam Machining, Chemical Machining Processes, Ultrasonic Machining, Jet Machining Processes.
In this topic, we are going to discuss Laser Beam Machining (LBM). But before going to the main topic, we will see what is LASER?
LASER stands for "Light Amplification by Stimulated Emission of Radiation". LASER is an effect of resonant effect and the output is a coherent electromagnetic field.

Principle of Laser Beam Machining:

The mechanism of material removal during Laser Beam Machining includes different stages such as
  1. Melting.
  2. Vaporization.
  3. Chemical degradation
When a high energy density of the laser beam is focused on the work surface, thermal energy is absorbed which heats and transforms the work volume into a molten, vaporized or chemically changed state that can be easily removed by the flow of high pressure assist gas jet.

Construction of Laser Beam Machining (LBM):

The laser beam machining setup is shown in the figure below.
Laser Beam machining
Laser Beam Machining

It consists of a stimulating light source (Xenon flash lamp) and a laser rod.
A laser rod or Laser tube consists of a pair of mirrors, which are placed at each end of a tube.
This setup also consists of a flash tube/lamp (i.e. energy source), laser, power source, focusing source, and cooling system.

Advantages and Applications of Laser Beam Machining

The whole setup is fitted in an enclosure that has a highly reflective surface inside it.
The laser used in the process may be solid, liquid or gaseous type. The solid type carries reflective coatings at their ends and gaseous type produces continuous laser beams. This laser beam produced is suitable for welding and cutting operations.
The most commonly used laser is Ruby.
In some applications, the helium-neon laser is also used.

Working of Laser Beam Machining:

In the operation of the machine, the optical energy (light) radiated from the flash lamp is focused on the laser rod (tube), from where it is reflected with the help of mirrors and accelerated in its path.
This reflected light is emitted in the form of a slightly divergent beam. 
A lens is placed in the path of this beam of light which converges and focuses the light beam on the component that is to be machined i.e. workpiece.
This impact of the laser beam on the workpiece melts the work material and due to this, it vaporizes.
Therefore, it is also called a thermal cutting process.

Laser Machining System:

The figures shown below shows the different types of laser machining systems.
Fig (a) is a spiral flash lamp in which a ruby rod is kept inside the lamp.
Fig (b) is a straight flash lamp and cylindrical mirror with an elliptical cross-section.
Fig (c) is another laser machining system in which a circular reflecting cylinder is shown.
Fig (d) shows four flash lamps arranged around the ruby rod.
Laser Beam Machining (LBM) - Principle, Construction and Working Laser Beam Machining (LBM) - Principle, Construction and Working Reviewed by Admin on 01:58 Rating: 5

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