Laser Beam Machining (LBM) – Construction, Working, Advantages

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┬ástands 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 that assist gas jet.

Construction of Laser Beam Machining (LBM)

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

Laser Beam Machining diagram
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. 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 the 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 show the different types of laser machining systems.
IMG 20150404 013447 1428091553227

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 Advantages and Disadvantages

Laser beam machining advantages and disadvantages are discussed below.

Advantages of Laser Beam Machining

  1. In the Laser beam Machining (LBM) process there is no direct contact between the tool and the workpiece, hence there is no issue of tool wear.
  2. Machining can be done in any environment.
  3. Refractory materials can be easily worked.
  4. Easy machining of brittle, non-metallic, and hard materials.
  5. Used for welding of dissimilar metals.
  6. Extremely small holes can be drilled easily.

Disadvantages of Laser Beam Machining

  1. LBM is applicable only for thin sections and where a small quantity of material is removed.
  2. Control of hole size is difficult.
  3. Holes drilled may have a slight taper formation, hence not suitable for large holes.
  4. The durability and reliability of the system are limited.
  5. Due to the low production rate, the efficiency of the system is low.
  6. The initial cost and operating cost of the system are high.
  7. Highly skilled operators are required.

Applications of Laser Beam Machining

  1. LBM is used for the trimming of sheet metal, carbon resistors, and plastic parts.
  2. It is used for drilling small holes in the materials like tungsten, ceramics which are very hard.
  3. LBM is also suitable for dynamic balancing of precise rotating components lie watches.
  4. Cutting complicated profiles on thin films for making Integrated Circuits, engraving patterns on suitable thin films or sheets.

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