Laser beam welding

Laser beam welding:

For joining pieces of metal or thermoplastics through the use of a laser the laser beam welding process is mostly preferred.

Generally laser beam welding is liquid-phase (fusion) welding process.

Laser beam welding diagram
Fig. 1 Laser beam welding diagram

In this process the metal is joined by melting their interfaces.

In short it can written as the LBW.

The process is frequently used in high-volume applications using automation, as in the automotive industry.

This LBW process depends on keyhole or penetration mode welding.

Holes produced by laser beam welding
Fig. 2 Holes produced by laser beam welding

The process in which the two metal pieces are joined together by the use of laser then this process is known as LBW.

The focus of the laser beam is directed on the cavity between the two metal pieces which have to be joined.

When there is enough energy in laser beams at that time the beam strikes the metal pieces and produces heat that melts the material from the two metal pieces and fills the cavity.

WORKING PRINCIPLE OF LASER BEAM WELDING:

When electrons of an atom get excited by absorbing some energy it returns back to its ground state after emitting a photon of light after taking some time.

By stimulating the emission of radiation we get the high energy concentrated laser beam and also increase the concentration of emitted photon.

MAIN PARTS USE IN LASER BEAM WELDING:

Laser Machine:

For the purpose of producing a laser for welding, laser machine is used.

The main components required for the laser machine are mentioned below.

Power Source:

For producing a laser beam a high voltage power source is applied around the laser machine.

CAM:

This machine run under computer.

In this, the laser machine is integrated with the computers to perform the welding process.

When the welding process by laser is going on at that time all the controlling actions are done by the CAM.

For greater extent cam speeds up the welding process.

CAD:

It is called as Computer-aided Design.

CAD can also be useful to design job for welding.

How to design the workpiece and how the welding is performed, for that here the computers are used.

Shielding Gas:

Shielding gas may be used in order to prevent the workpiece from oxidation during the welding process.

TYPES OF LASER USED:

Gas lasers:

It uses mixtures of gases as a lasing medium to produce laser. Mixtures of gases such as nitrogen, helium, and CO2 are used as the lasing medium.

Solid-state laser:

It uses several solid media such as synthetic ruby crystal (chromium in aluminum oxide), neodymium in glass (Nd: glass), and neodymium in yttrium aluminum garnet (Nd-YAG, most commonly used).

Fiber laser:

Optical fiber itself is the lasing medium in this type of laser.

CHARACTERISTICS OF LASER BEAM WELDING:

There is a high power density of laser beam.

It is of the order 1 MW/cm2.

There are small heat-affected zones created because of this high energy density.

Heating and cooling is high in the LBW.

In this coherent ( having the same phase) and monochromatic ( i.e. having the same wavelength), laser beams are produced.

The laser beam welding process effectively works to weld smaller sizes spot, but the spot sizes can vary from 2 mm to 13 mm.

It produces high-quality weld.

This welding process is most popular in the automotive industry.

ADVANTAGES:

It produces high weld quality.

For the purposes of large volume production LBW can be easily automated with robotic machinery.

Sheet metal cutting with laser beam
Fig. 3 Sheet metal cutting with laser beam

No electrode is required.

Due to non-contact process it has no tool wear.

It reduces the time taken for the welding thick section.

It is capable for welding the areas which are not easily accessible.

It has the ability to weld metals with dissimilar physical properties.

There is no vacuum required, it can be weld through air also.

DISADVANTAGES:

The initial cost is high.

The equipment used in LBW has a high cost.

High maintenance cost.

Due to the rapid rate of cooling, cracks may be produced in some metals.

High skilled labor is required to operate LBW.

The welding thickness is limited to 19 mm.

The energy conversion efficiency in LBW is very low. It is usually below 10%.

LASER BEAM APPLICATIONS:

In the automotive industry the laser beam welding is much dominant.

Where large volume production is required then this process is used.

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