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Short notes for GATE Mechanical Engineering - Laser Beam Machining (LBM)

In the last article we learnt about the Electron beam machining, and in this article, we will learn about the next unconventional machining process - Laser Beam Machining (LBM).

Laser Beam Machining:

Laser is the term used for the phenomenon of 'amplification of light by stimulated emission of radiation'. The setup consists of a stimulating light source (like xenon flash lamp) and a laser rod. The light radiated from the flash lamp is focused on the laser rod (laser tube), from where it is reflected and accelerated in the path. This light is emitted in the form of a slightly divergent beam. A lens is used suitably in the path of beam of light which converges and focusses the light beam onto the workpiece to be machined. This concentration of laser beam on the workpiece melts the work material and vaporises it. 

The setup mainly consists of:

  • A laser rod or tube
  • A pair of mirrors - one at each end of the tube
  • A flash tube or lamp (energy source)
  • An amplifying source (laser)
  • A power supply source
  • A cooling system
  • A lens (foucs in source)

The main setup is fitted inside an Enclosure, which carries a highly reflective surface inside. 

Advantages of LBM:

  • Any material can be easily machined, irrespective of its structure and physical and mechanical properties
  • Unlike conventional machining, there is no direct contact between the tool and the workpiece and no involvement of large scale cutting forces
  • Tool wear is non-existent
  • Can be effectively used for welding of dissimilar metals
  • Small heat effected zone around the machined surface
  • Very small holes and cuts can be made with fairly high degree of accuracy

Disadvantages of LBM:

  • High initial investment needed
  • High operating cost
  • Highly skilled operators are needed
  • Production rate is low
  • Its application is only limited to thin sections and where very small amount of metal removal is involved

Applications of LBM:

  • Trimming of carbon resistors
  • Drilling small holes in hard materials like Tungsten and ceramics
  • Cutting complex profiles on thin and hard materials, like thin films for making ICs
  • Dynamic balancing of precision rotating components, like watches
  • Trimming of sheet metal and plastic parts

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