Laser Beam Machining presentation prepared by Joshan Pithava student of B.Tech Mechanical from Chhotubhai Gopalbhai Institue of Technology.

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Introduction
Type of Lasers
Working Principle
Sub System
Laser Characteristic
Laser Cutting Parameters
Advantages of Laser Beam
Disadvantages of Laser Beam
Application Of Laser Beam

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• A laser beam machining is a non-conventional machining method in which the operation
is performed by laser light.
• The laser light has maximum temperature strikes on the workpiece, due to high temp the
workpiece gets melts.
• The process used thermal energy to remove material from a metallic surface.
• There are three main components to any laser system: laser medium means for exciting the
laser medium to the state of excitation which is the source of energy, and the optical
feedback system. Some other provisions such as cooling system for the mirrors, a guiding
system for guiding the laser beam

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• On the basis of the media used for the production of
the laser it is classified as:
1. Gas Laser
 In gas laser type gases are used as medium to
produce lasers. The commonly used gases are He-
Ne, Argon and Co2.
 The device of a CO2 laser produces light when
electricity runs through a gas-filled tube.
 The CO2 lasers which we use for machining are
usually run over 25 and 100 W.

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2. Solid State Laser
 A solid-state laser is a laser that uses a gain medium that is
a solid, rather than a liquid as in dye lasers or a gas as in gas
lasers.
 Generally, the active medium of a solid-state laser consists of
a glass or crystalline "host" material, to which is added a
"dopant" such
as neodymium, chromium, erbium, thulium or ytterbium.
 The most common state medium used are neodymium-doped
yttrium aluminum garnet (Nd:YAG). Neodymium-doped
glass (Nd:glass) and ytterbium-doped glasses or ceramics

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• Laser Beam Machining works on the principle of conversion of electrical energy of flash lamp into
heat energy to emit the laser beam by pumping the energy.
• In this process, the Laser Beam is called monochromatic light, which is made to focus on the
workpiece to be machined by a lens to give extremely high energy density to melt and vaporize any
material.
• The Laser Crystal (Ruby) is in the form of a cylinder as shown in the above figure or Diagram with
flat reflecting ends which are placed in a flash lamp coil of about 1000W.
• The Flash is simulated with the high-intensity white light from Xenon. The Crystal gets excited and
emits the laser beam which is focused on the workpiece by using the lens.
• The beam produced is extremely narrow and can be focused to a pinpoint area with a power density
of 1000 kW/cm2. Which produces high heat and the portion of the metal is melted and vaporizes.

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1. A Pumping Medium
2. Flash tube/Flash Lamp
3. Power Supply
4. Capacitor
5. Reflecting Mirror
 Other basic system:
1. A pair of Mirror
2. An Amplifying Source
3. A Cooling System
4. Lens

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Application Type of Lasers
Large holes up to 1.5mm diameter Ruby, Nd-glass, Nd-YAG
Large holes Nd-YAG, CO2
Small Holes > 0.25mm diameter Ruby, Nd-glass, Nd-YAG
Drilling (punching or percussion) Nd-YAG, Ruby
Thick Cutting CO2 with gas assist
Thin slitting of metals Nd-YAG
Thin slitting of Plastics CO2
Plastics CO2
Organics, Non-metal Pulsed CO2
Ceramics Pulsed CO2, Nd-YAG

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Parameters
Process Parameters
Focusing of
Laser Beam
Focal
Position
Process Gas
and Pressure
Nozzle
Diameter
Stand off
Distance
Cutting
Speed
Beam Parameters
Wavelength
Power
Spot Size
Pulsed Laser
Power

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1. Wavelength
• It has important effect on material‘s surface absorptivity.
• For a specific material type, there is a certain wavelength which can have
maximum absorption of laser energy with a lowest reflection.
• Due to the shorter wavelength of fiber lasers (in the range of 1 μm almost
the same as Nd-YAG laser) compared to CO2 lasers (10.6μm), it leads to
the higher absorption in metallic material.
2. Spot Size
• Spot size is the irradiated area of laser beam. In laser cutting application, it
is required to focus beam into minimum spot size.
• Due to the better beam quality of fiber laser with very low divergence, the
user can get spot diameters smaller than conventional lasers producing
longer working distances.

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1. Stand off Distance
• The stand-off distance, which is the distance between the nozzle and the work
piece, is also an important parameter.
• The stand-off distance is usually selected in the same range as the diameter of
cutting nozzle-between 0.5 and 1.5 mm-in order to minimize turbulence.
2. Cutting Speed
• The cutting speed must be balanced with the gas flow rate and the power.
• As cutting speed increases, the cutting time decreases and less time for the heat to
diffuse sideways and the narrower the HAZ.
• When the cutting speed is too low, excessive burning of the cut edge occurs,
which degrades edge quality and increases the width of the HAZ.

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3. Nozzle Diameter
• Nozzle is used to deliver the assist gas. The nozzle has three main functions in the
laser cutting process: to ensure that the gas is coaxial with the beam; to reduce the
pressure to minimize lens movements and misalignments; and to stabilize the
pressure on the work piece surface to minimize turbulence in the melt pool.
4. Process Gas and Pressure
• In the process of oxygen cutting, the presence of oxygen contributes to an
exothermic reaction, which effectively increases the laser power. It results into
high cutting speeds and the ability to cut thick material.
• When cutting thick material, the gas pressure must decrease with the increasing
thickness, in order to avoid the burning effect, whereas the nozzle diameter is
increased.

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5. Focal Position
• In order to get optimum cutting result, the focal point position must be controlled. There are two reasons: the first
reason is that the small spot size obtained by focusing the laser beam results in a short depth of focus, so the focal point
has to be positioned rather precisely with respect to the surface of the work piece; the other one is differences in
material and thickness may require focus point position alterations.
6. Focusing of Laser Beam
• The focal length of lens is about the distance from the position of focal lens to the focal spot.
• In the fiber laser system, the laser beam is delivered by the fiber optics and use a collimator to form the divergent laser
beam.
• After that, it comes to the focusing lens or mirror and it focuses the parallel laser beam onto the work piece.
• The cutting process requires the spot size is small enough to produce the high intensity power.

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• The basic assumption to analyze the material removal rate:
1. The intensity of laser beam does not vary with the time.
2. Laser beam is uniform over the entire area of hotspot.
3. The material being removed is both melting and evaporating.
4. The steady state ablation is characterized by constant rate of material removal and by the establishment of a steady state
distribution.

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• According the above assumption, the steady temperature distribution is given by:
(T – T0) / (Tm - T0) = e-vx/α
Where,
T = temperature at distance x below the ablating the surface
T0 = initial uniform temperature of the workpiece
Tm = melting point of the workpiece
V = steady ablation velocity

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• It can be focused on very small diameters. It produces a huge amount of energy, about 100 MW per
square mm area.
• It is capable of producing a very accurately placed hole
• Laser beam machining's have the ability to cut or engrave almost all types of materials when conventional
machining processes fail to cut or engrave any material.
• It can be focused to a very small diameter.
• Since there is no physical contact between the tool and workpiece. The wear and tear in this machining
process is very low and hence it requires low maintenance cost

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• High initial cost. This is because it requires many accessories that are important to the machining process
by Laser.
• Laser beam machining requires a highly trained worker to operate the machine.
• Low production rate since it is not designed for the mass production.
• It requires a lot of energy for machining process.
• It is not easy to produce deep cuts with the w/p that has high melting points and usually cause a taper.

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• The laser beam machining is mostly used in automobile, aerospace, shipbuilding, electronics, steel and
medical industries for machining complex parts with precision.
• In heavy manufacturing industries, it is used or drilling and cladding, seam and spot welding among
others.
• In light manufacturing industries, it is used for engraving and drilling other metals.
• In the electronic industry, it is used for skiving (to join two ends) of circuits and wire stripping
• n medical industry, it is used for hair removal and cosmetic surgery.

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