Laser Cutting

1. A.V.Wijayasundara
ME5125 – Manufacturing Processes: Advanced Aspects
2013

2.  Light Amplification by Stimulated Emission of
Radiation
 Laser light is very different from normal light
 The light released contains one specific
wavelength of light
 Generated waves are "in phase" with one another
 Laser light is very tight beam, very strong and
concentrated
 These properties are achieved by Stimulated
Emission

3.  Stimulated Emission
 An atom absorbs energy in the form of heat, light, or
electricity
 Electrons may move from a lower-energy orbit to a
higher-energy orbit
 lasing medium is “pumped” with intense flashes
of light or electrical discharges to get the
electrons into an excited state

4.  lasing medium
 Certain crystals, typically doped with rare-earth ions
(neodymium, ytterbium, erbium)
 Glasses, silicate or phosphate glasses, doped with
laser-active ions
 Gases, mixtures of helium and neon
 Semiconductors, gallium arsenide (GaAs), indium
gallium arsenide (InGaAs), or gallium nitride (GaN)
 Liquids, in the form of dye solutions as used in dye
lasers
 Once the lasing medium is pumped it contains a
collection of atoms with some electrons sitting
in excited levels

5.  As this excited electrons are returned to natural
levels it releases energy form of photons
 Two identical atoms with electrons in identical
states will release photons with identical
wavelengths.

6.  If an emitted photon encounter another atom
that has an electron in the same excited state,
stimulated emission can occur
 The first photon can stimulate or induce atomic
emission such that the subsequent emitted
photon from second atom vibrates with the same
frequency and direction as the incoming photon

7.  Key is pair of mirrors - one at each end of the
lasing medium
 Photons with a very specific wavelength and
phase reflect off the mirrors to travel back and
forth through the lasing medium
 This cause the emission of more photons of the
same wavelength and phase
 Mirror at one end is half-silvered so it reflects
some light and lets some light through.
 The light that makes it through is the laser light

9.  Not only light frequency
 Infrared laser
 Ultraviolet laser
 X- ray laser

10.  CD players
 dental drills
 metal cutting machines
 measuring systems
 Tattoo removal
 hair replacement
 eye surgery
 Military applications
 Security devices
 Entertainment
 fingerprint detection

11.  Technology that uses a laser to cut metal
 mostly used to cut flat sheet material or
structural or piping metals
 Cutting done by directing the output of a high-
power laser to work piece
 material either melts, burns, vaporizes away
 Types of lasers used (Lasing medium)
 CO2 laser - suited for cutting, boring, and engraving
 Neodymium (Nd)laser – used for high-energy pulses low
repetition speed jobs
 neodymium yttrium-aluminium-garnet (Nd-YAG)
lasers – used when very high power is needed

12.  These laser beams are focused with lenses to be
able to cut through
 Typical process laser 0.25 mm in beam width
 Focus 1000 to 2000 watts of energy

13.  Assisting gas plays an important role
 provides a mechanical force to eject the molten
 cools the cut zone by forced convection
 Nitrogen, compressed air used
 reactive gas such as oxygen - chemical reaction
between the assist gas and the molten material
produces additional energy that enhances the cutting

14.  Vaporization cutting
 focused beam heats the surface of the material to
boiling point and generates a keyhole
 deepening the hole
 wood, carbon and thermoset plastics are cut by this
method
 Melt and blow (fusion cutting)
 material heated to melting point then a gas jet blows
the molten material out
 Metals are cut by this method
 Thermal stress cracking
 Brittle materials like glass cut by this method
 Laser guide a fracture on desired path

15.  Very less clamping force needed
 Very small and precision cuts and depths are
possible
 Very small, negligible heat effected zone in work
piece
 can be applied to any material that can properly
absorb the laser irradiation
 Final smooth surface finish with single cut
 No edge burr
 Very small drill holes
 3-D movement of cutter is very flexible

16.  Copper and aluminum hard to cut with laser
because they reflect laser and thermal conductivity
 Production rate will be low for big jobs
 Generally involves high power consumption
 Generally Imposable to cut thickness more than 6
mm