Working of Laser beam machining process. Its one kind of non traditional or advanced manufacturing process.Production of laser beam and with the use of lasers how can material can be removed is to be explained over here...
Actual LBM process.
Mechanism of material removal.
Advantages of LBM.
Disadvantages of LBM.
The term “laser” is an stands for Light Amplification by
Stimulated Emission of Radiation. LBM is nontraditional thermal
In thermal removing processes, thermal energy, provided by a heat
source, melts or vaporizes the volume of the material to be
Among thermal removal methods,
Electrical discharge machining or EDM is the oldest and most widely
Electron-beam (EBM) and laser beam machining (LBM) are newer
thermal techniques also widely accepted in industry today.
Laser beam machining
is based on the
of electrical energy
into light energy and
then to thermal
• 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.
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.
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.
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.
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
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
4) At the each reflection a certain loss occurs
It is very interesting that laser has to be used on materials where it absorbs
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
Optical energy is converted into heat energy upon impact and temperatures
generated can be high to melt and/or vaporize any material.
Rapid rise in
Gas Assist Mechanism of
Excellent control of the laser beam with a stable motion system achieves
an extreme edge quality. Laser-cut parts have a condition of nearly zero
edge deformation, or roll-off
It is also faster than conventional tool-making techniques.
Laser cutting has higher accuracy rates over other methods using heat
generation, as well as water jet cutting.
There is quicker turnaround for parts regardless of the complexity,
because changes of the design of parts can be easily accommodated.
Laser cutting also reduces wastage.
The material being cut gets very hot, so in narrow areas, thermal
expansion may be a problem.
Distortion can be caused by oxygen, which is sometimes used as an assist
gas, because it puts stress into the cut edge of some materials; this is
typically a problem in dense patterns of holes.
Lasers also require high energy, making them costly to run.
Lasers are not very effective on metals such as aluminum and copper
alloys due to their ability to reflect light as well as absorb and conduct
heat. Neither are lasers appropriate to use on crystal, glass and other