Outline:

1
MENG 439
Dr. L. K. Gaafar
Laser Technology
Prepared by Eng. Ahmad Hassan Sayed
2
Outline
Laser Technology

• Laser Technology
• Processes
• Cutting
• Drilling
• Welding
• Rapid Prototyping
• Other Precise Measurement, Heat Treatment,
  Scribing
• General Advantages and Disadvantages
• Economics
• Safety measures

3
Laser Technology
Definition and Operation

• Laser is an abbreviation of light amplification
  by stimulated emission of radiation
• Laser Beam operation are based on producing high
  energy laser beam that melts and vaporizes the
  material.
• Can be used to cut, weld, drill by varying both
  power and beam intensity, focus, and duration.

4
Laser Technology
Laser Beam

• Beam diameter is about 0.013 inch.
• Continuous Mode is preferred for straight and
  mildly contoured cuts (cutting is fastest).
• Pulse Mode preferred for thin materials and it
  enables tight corners and intricate details to be
  cut without excessive burning. Pulse duration
  0.25sec

5
Laser Technology
Beam Generation

• A relatively weak light flash bounces back and
  forth between the mirrors causing the lasing
  material to produce energy (photons)
• These photons accelerate the intensity of the
  beam of light which will cause the beam to cross
  the partial mirror after reaching a certain
  intensity.
• A lens focuses the beam on the work piece causing
  portions of it to melt and vaporize.

6
Laser Technology

• Beam Generation

Schematic diagram of a laser beam machine1
7
Laser Technology
Lasing Materials

• YAG Lasers (Yttrium-Aluminum-Garnet)
• Wavelengths 1064 nm
• Power up to 5 kW
• Pulsed and continuous wave
• CO2 Lasers
• Wavelengths 10.6 ?m
• Power up to 100 kW
• Pulsed and continuous wave

8
Laser Technology
Laser Beam Features

• High Power.
• Monochromatic Same wave length (same color).
• Coherent light waves in phase.
• Non-contact.

9
Laser Technology
Physical Parameters of Workpiece Material

• Reflectivity.
• Thermal Conductivity.
• Specific Heat
• Latent Heat

• The lower these parameters the more efficient the
  process since less energy is required to melt and
  vaporize the material.

10
Laser Technology
Beam Delivery System

• 1. Hard Optic Delivery (Moving workpiece)
• relatively inexpensive.
• can accommodate large heavy lasers.
• operate quick (20 m/min).
• but heavy large piece limited.

Hard optic Delivery3
11
Laser Technology
Beam Delivery System

• 2. Hard Optic Delivery (Moving Laser)
• relatively inexpensive.
• can accommodate large heavy workpieces.
• but compact laser system required (solution
  optical fiber), but the load of laser is
  constant, easy to design.

Hard optic Delivery3
12
Laser Technology
Beam Delivery System

• 3. Fiber Optic Delivery
• Quick move (more than 100m/min).
• 3D Structure
• but expensive.

• Beam produced is transmitted through fiber optic
  cables to a pointer that is attached to a moving
  arm this facilitates moving faster (reduced load
  on arm) and in small areas

Fiber optic delivery
13
Processes
Applications of Laser in manufacturing
14
Processes Cutting

• Cutting starts by drilling a hole then moving the
  beam in a programmed path.
• A stream of assist gas is used to
• blow the molten metal
• Cool workpiece
• Minimize heat affected zone

Laser Processing System
15
Processes Cutting
Assist Gases used with Different Materials

• Mild steel Oxygen
• Stainless steel Oxygen or nitrogen (nitrogen
  leaves an oxide free edge that can improve
  weldability)
• Aluminum Nitrogen
• TitaniumArgon (an inert gas because of its
  reactivity)
• Nonmetals Air or inert gas

16
Processes Cutting

• Cutting Temperature could reach 11000oC.
• The more uniform the thermal characteristics of
  component the better the cut and less thermal
  damage to the material.
• Cutting Speed depends on
• (can reach 1000in/min in nonmetals)
• Material
• Thickness

17
Processes Cutting

• Cutting Capabilities (Thickness)
• Acrylic and composites 1 in
• Aluminum ¼ in
• Mild steel 0.625 in
• Stainless steel 5/16 in
• Titanium ¼ in

18
Processes Cutting

• Applications

Height following Laser nozzle3
Examples of laser cutting using pulsed CO2 Laser3
19
Processes Cutting

• Advantages
• Narrow kerf and heat affected zone
• Although cutting produces a thin recast surface,
  no post-cut finishing is required
• Economic alternative for materials that are
  difficult to cut by conventional
  methods(plastics, wood, and composites)
• Narrow slots
• Closely spaced patterns
• Does not require smooth surface

20
Processes Drilling
Description

• The repeated pulsed laser beam vaporizes the
  material layer by layer until a through hole is
  formed.
• Larger diameters can be contoured after drilling
  the through hole if desired.
• Blind holes are theoretically possible but not
  practical.
• Hole diameter depends on material thickness.
• Cutting and drilling are performed on the same
  unit.

21
Processes Drilling
Characteristics

• Drill micro-holes in metals as thick as 0.1in
• LD ratio 101
• Cutting Speed decreases? depth increases but
• Generates irregular holes
• Recast layer increases
• Heat affected zone increases

22
Processes Drilling

• Applications
• Bleeder holes for fuel pump covers
• Drilling holes in delicate medical materials
• Drilling holes in small polymer tubes
• Drills tiny holes in turbine blades of jet engine

23
Processes Drilling

• Advantages
• Burr free holes
• Eliminates drill breakage and wear
• Drills in difficult to access areas, curved
  surfaces and parts incased in glass
• Drills holes of almost any shape
• High quality and precision holes
• Close tolerances
• Limitations
• Holes up to 1 deep in plastics and ferrous
  metals, and 0.125 in reflective materials.

24
Processes Welding
Description

• High intensity beam produces a cause the material
  to melt and flow into the channel (gap) as the
  beam advances.
• Careful joint preparation is needed to produce
  the thin gap.
• forms a very thin heat affected zone and little
  thermal distortion.

Schematic diagram of laser beam welding operation
Picture From class.et.byu.edu/mfg130/processes/d
escriptions/thermaljoining/laserbeamcutting.htm
25
Processes Welding
Characteristics

• Solidifies quickly
• Filler material is used if gap is large.
• Inert (Shielding) gas is may be used to prevent
  oxidation of weld pool.
• Can be used to produce deep penetration welds
• Effective with thin workpiece

Schematic diagram of laser beam welding operation
Picture From class.et.byu.edu/mfg130/processes/d
escriptions/thermaljoining/laserbeamcutting.htm
26
Processes Welding

• Applications
• Razor blades 13 pinpoint welds 0.5 mm in
  diameter
• Electronic circuits

Razor blades are spot welded using laser
27
Processes Welding

• Advantages
• Does not require vacuum
• Better quality of weld
• Beam easily shaped, directed, and focused
• No direct contact is necessary to produce a weld
• Encapsulated (with transparent containers) and
  inaccessible areas can be welded
• Can be made with access to only one side of joint
• Increase speed and strength of welding
• Produces maximum penetration and minimum
  distortion in the material

28
Processes Rapid Prototyping

• 3D CAD Software is used to slice a 3D model into
  2D horizontal layers packed on top of each other
• A laser beam then starts to build the first layer
  by melting and fusing powder metal.

Schematic diagram of a rapid prototyping machine
29
Processes Rapid Prototyping

• The layer then solidifies and fresh power is
  added on top of it for the next layer
• The laser beam proceeds building the physical
  prototype layer by layer until it is done.
• Model is cleaned, cured, and then can be used for
  testing in environments similar to that of the
  final product

Schematic diagram of a rapid prototyping machine
30
Processes Rapid Prototyping

• Applications

Models created by rapid prototyping 7
31
Processes Rapid Prototyping

• Advantages
• Speeds up the design and manufacturing process.
• Reduces product development cost.
• Allows for instant feedback to design engineers.
• Allows for design corrections at an early stage.
• The model is used in pre-production planning and
  tool design.

32
Processes Rapid Prototyping

• Disadvantages
• The generated model has shrinkage cracks
• The model has high hardness, which makes it
  brittle
• Thick walled structures cant be built up very
  well

33
Processes Measurements
Description

• Helium-Neon laser beam is split into two beams
  one beam goes to a reference point and reflects
  back using a retro-reflector, while the other
  hits the object.
• Then the two beams are recombined, and their
  relative motion creates a frequency shift.
• This shift is then converted into a distance
  measurement.

34
Processes Measurements

• Applications
• To align and calibrate machine tools
• Useful in Large assembly jigs
• Non-contact used to inspect hot rolled material

35
Processes Heat Treatment
Description and Characteristics

• Produces hardened surfaces
• For wide variety of geometries
• Can work on limited area
• Produces little distortion

Cam Part 14
36
Processes Scribing
Description and Characteristics

• Composed of series of closely placed holes
• To produce lines and characters with different
  fonts on materials
• As wide as laser beam
• Set to a specific tolerance depth

Application of scribing
Cut, Scribe and Weld operations
37
General Advantages

• Operates in fully automated environment
• Minimum heat affected zone compared to other
  thermal processes
• Clean
• Small clamping force is applied
• Can be used with metals, nonmetals, and
  composites
• Excellent surface quality
• Minimum thermal stresses on the material
• No tooling required

38
General Disadvantages

• Requires specially trained operators
• Not for mass metal removal processes
• Requires greater control of joint tolerances
• Expensive equipment
• Consumes much energy

39
Economics

• Expensive equipment
• Requires skilled operators
• Compensated by
• Fast material removal rate (0.5-7.5m/min) ? high
  production rates
• Finishing costs are eliminated
• Can be automated ? reducing operational costs

40
Economics

• Cost of Laser Cutting Machine
• New 200,000
• Used starting 30,000
• CNC 750,000

41
Safety Measures

• Lasers can burn and blind
• Eyes and skin should be protected from scattered
  beams
• Even low powers can cause damage to retina
• Operator should wear gas masks to protect
  against generated fumes