This document discusses the principles and process of laser cutting. It begins by explaining the basics of how a laser works using stimulated emission to produce a coherent beam of single-wavelength light. It then describes how various materials can be used as the lasing medium, and how mirrors produce stimulated emission to generate the laser beam. The key steps of laser cutting involve focusing the laser beam using lenses to cut materials by melting, burning, or vaporizing away material. An assisting gas is used to eject molten material and cool the cut zone. Laser cutting enables precision cuts with little heat effect and no burrs or edges.

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