LASER BEAM MACHINING PPT BY POLAYYA CHINTADA USED FOE ENGINEERING STUDENTS AND POLYTECHNIC STUDENTS

1. Laser Beam Machining (LBM)
Prepared by,
Chintada Polayya

2.  Content
 Introduction.
 Basic Principle.
 Laser Concept.
 Actual LBM process.
 Mechanism of material removal.
 Advantages of LBM.
 Disadvantages of LBM.

3.  Introduction:-
 The term “laser” is an stands for Light Amplification by
Stimulated Emission of Radiation. LBM is nontraditional thermal
process.
 In thermal removing processes, thermal energy, provided by a heat
source, melts or vaporizes the volume of the material to be removed.
 Among thermal removal methods,
a. Electrical discharge machining or EDM is the oldest and most
widely used.
b. Electron-beam (EBM) and laser beam machining (LBM) are newer
thermal techniques also widely accepted in industry today.

4. Principle;-
Laser beam machining
is based on the
conversion
of electrical energy
into light energy and
then to thermal
energy.

10. • Laser Concept
 The electrons are charged particles, they carry some energy. The
energy related with the orbit in which the electrons revolve.
 Generally the electrons are present in the outer most orbit of the
atom take part in the process of energy absorption or emission.
 Ground state, the state with lowest energy is the most stable state for the
electrons. After absorbing the energy electron jump to the higher energy
state and staying there for some seconds jump to the ground state and
release the absorbed energy.

11.  This jump may be in two stages:-
 Electron from higher state may not come directly to the ground state but
may halt for some micro seconds on some intermediate state before finally
coming to the ground state.
 The period for which electron stays in a higher energy state is known as the
lifetime of that energy state.
 Lasing action:-
 The emission of photon is not done by only one atom at upper energy level
but on the influence of external light, a sort of chain reactions occurs and
one after other atoms start emitting photons. Thus whole avalanche dumps
down together. This is called lasing action.

12.  Not all the materials are suitable for producing laser beam.
 One of the most common laser materials and also one capable of
delivering high power is the chromium on a ruby crystal.
 Crystal ruby is aluminum oxide.
 Generally the ruby rod 1 cm diameter and 10 cm long with ends
polished fully is used.

16. Actual LBM Process
 1) In the beginning in atom all the crystals are in ground state
 2) When the light is flash over the crystal, most of the atoms are raised to
the excited state. Some light waves incline to the axis of the crystal will
leave the box either after only a few reflections or without strike on mirror.
 3) Some of the waves that travel parallel to the axis of the crystal, will
spontaneously emit photon from chromium ions. These photon stimulate
another atom to contribute a second photon.
This process continues as the photons are reflected to and fro between the
mirror.
 4) At the each reflection a certain lossoccurs

17.  It is very interesting that laser has to be used on materials where it absorbs
laser energy.
 Upon absorption of the laser energy, there is rapid rise in the temperature
leading once again to melting and vaporization and material removal.
 Although several types of laser exist, all lasers produce (emit) intense,
coherent, highly collimated beam of single wavelength light. In material
processing applications, this narrow beam is focused by an optical lens to
produce a small, intense spot of light on the work piece surface, as shown in
figure.
 Optical energy is converted into heat energy upon impact and temperatures
generated can be high to melt and/or vaporize any material.

18. Absorb the
laser energy
Rapid rise in
temperature
Melting &
evaporation
Material
Removal
GasAssist Mechanism of
Material
Removal
In
LBM

22. Thank You…..!!