Download - laser_beam_machining
-
8/7/2019 laser_beam_machining
1/46
EPP 212
Advanced Manufacturing Technology
Group Seminar
-
8/7/2019 laser_beam_machining
2/46
L
B
L
B
AASSEERR
EEAAMM
MACHI IN NGACHININM G
-
8/7/2019 laser_beam_machining
3/46
-
8/7/2019 laser_beam_machining
4/46
Laser beam machining process uses highly coherent lightsource.
This beam can be focused by means of a lens on a verysmall spot in the work piece.
The high power radiation of laser gives rise to hightemperature on a small area of work piece. This initiatesthe cutting process in the work material.
The equipment consists of ruby crystal placed inside aflash lamp. The flash lamp is used to produce highintensity light rays.
-
8/7/2019 laser_beam_machining
5/46
The ruby crystal is thus simulated and this produces
highly spatial laser beam. When the rays hit the work
surface it causes partial or complete vaporization ofsurface material.
-
8/7/2019 laser_beam_machining
6/46
Design
Consideration
-
8/7/2019 laser_beam_machining
7/46
Non-reflective workpiece surfaces are
preferable
Sharp corners are difficult to produce; deepcuts produce tapers
Consider the effects of high temperature on
the workpiece material
-
8/7/2019 laser_beam_machining
8/46
-
8/7/2019 laser_beam_machining
9/46
Laser Beam Machining (LBM) is thermalprocesses considering the mechanisms ofmaterial removal.
Laser Beam Machining or more broadly lasermaterial processing deals with machining andmaterial processing like heat treatment, alloying,
cladding, sheet metal bending. Laser stands for light amplification by stimulated
emission of radiation.
As laser interacts with the material, the energy ofthe photon is absorbed by the work material
leading to rapid substantial rise in localtemperature. This in turn results in melting andvaporisation of the work material and finallymaterial removal.
-
8/7/2019 laser_beam_machining
10/46
Similarly as can be seen in Fig. 9.6.1, laser beams canbe focused over a spot size of 10 100 m with apower density as high as 1 MW/mm2.
Electrical discharge typically provides even higherpower density with smaller spot size.
EBM and LBM are typically used with higher powerdensity to machine materials. The mechanism ofmaterial removal is primarily by melting and rapid
vaporisation due to intense heating by the electronsand laser beam respectively.
-
8/7/2019 laser_beam_machining
11/46
-
8/7/2019 laser_beam_machining
12/46
Laser can be used in wide range of manufacturing
applicationsy Material removal drilling, cutting and tre-panning
y Welding
y Cladding
y Alloying
Drilling micro-sized holes using laser in difficult to
machine materials is the most dominant application in
industry. In laser drilling the laser beam is focused over the
desired spot size. For thin sheets pulse laser can be
used. For thicker ones continuous laser may be used.
-
8/7/2019 laser_beam_machining
13/46
Typical Application
and
Product Made
-
8/7/2019 laser_beam_machining
14/46
4 Typical application
Material removal-CuttingWelding
CladdingSoldering
-
8/7/2019 laser_beam_machining
15/46
Method used in laser cutting
vaporization
melt and blow
melt blow and burn thermal stress cracking
scribing
cold cutting burning stabilized laser cutting
-
8/7/2019 laser_beam_machining
16/46
Laser Beam welding
LBW is a versatile process, capable of
welding carbon steels, HSLA
steels, stainless steel, aluminum,
and titanium The weld quality is high.
-
8/7/2019 laser_beam_machining
17/46
Laser Cladding
A method of depositing material by which a powdered orwire feedstock material is melted and consolidated by useof a laser in order to coat part of a substrate or fabricate anear-net shape part.
It is often used to improve mechanicalproperties or increase corrosion
resistance, repair worn out parts, and
fabricate metal matrix composites.
The powder used in laser cladding isnormally of a metallic nature, and is
injected into the system by either coaxial
or lateral nozzles.
-
8/7/2019 laser_beam_machining
18/46
Laser Soldering
A technique where a laser is used to melt and solder anelectrical connection joint. Diode laser systems based onsemiconductor junctions are used for this purpose.
The beam is delivered via an optical fiber to the
workpiece,with fiber Since the beam out of the end of the fiber
diverges rapidly, lenses are
used to create a suitable spot
size on the workpiece at a
suitable working distance. Awire feeder is used to supply
solder.
-
8/7/2019 laser_beam_machining
19/46
Product made by LBM
-
8/7/2019 laser_beam_machining
20/46
Advantage of Laser Beam
Machining
-
8/7/2019 laser_beam_machining
21/46
Easier workholding
Reduced contamination of workpieceReduced chance of warping the material that
is being cut
High precision (more precise and using less
energy when cutting sheet metal compared toplasma machining)
-
8/7/2019 laser_beam_machining
22/46
-
8/7/2019 laser_beam_machining
23/46
Consume electricity (eg. A typical 1500-watt
CO2 laser will have a running cost in the region of10 - 20 per hour.)
High initial capital cost
High maintenance cost
High purity gas (for the laser generating chamber)
Limited thickness of sheet metal can cut outcompared to plasma machining
Presence of Heat Affected Zone specially in gas
assist CO2 laser cutting
Thermal process not suitable for heat sensitive
materials like aluminium glass fibre laminate
-
8/7/2019 laser_beam_machining
24/46
AlternativeMethod
-
8/7/2019 laser_beam_machining
25/46
Press tools (working on the shearing principle) are avery quick and efficient way to produce components from
sheet or strip stock in large quantities, they are however
time consuming to set up and expensive to tool.
Machining and forming process, such as combining oflaser cutting and punching of sheet metal
eg. turret punch presses have been equipped with an
integrated laser head; the machine can punch or laser cut,but it cannot do both simultaneously
-
8/7/2019 laser_beam_machining
26/46
-
8/7/2019 laser_beam_machining
27/46
New laser cutters have positioning accuracy of10 micrometers and repeatability of 5micrometers.
This process is capable of holding quite closetolerances, often to within 0.001 inch (0.025mm) Part geometry and the mechanicalsoundness of the machine have much to dowith tolerance capabilities. The typical surface
finish resulting from laser beam cutting mayrange from 125 to 250 micro-inches (0.003mm to 0.006 mm)
-
8/7/2019 laser_beam_machining
28/46
-
8/7/2019 laser_beam_machining
29/46
Surface roughness is an effective parameter
representing the quality of machined surface.
surface roughness value reduces onincreasing cutting speed and frequency, and
decreasing the laser power and gas pressure
surface roughness value was found to bereduced on increasing pressure in case of
nitrogen and argon but air gives poor surfacebeyond 6 bar pressure. Also, surface finishwas better at higher speeds.
-
8/7/2019 laser_beam_machining
30/46
The surface roughness is minimum andlaser power has a small effect onsurface roughness but no effect onstriation frequency
Micromachining of 0.5 mm thick NdFeBceramic (magnetic material) usingpulsed Nd:YAG laser gives bettersurface finish in water as compared toair
-
8/7/2019 laser_beam_machining
31/46
-
8/7/2019 laser_beam_machining
32/46
LBM economics
Depend on number of parts manufactured onthat machine
One laser produced and used in differentmachine, can reduce investment costs of laser
Reduce time of production of laser, hencereduce steps to setting up machine
By increasing the technological compactness,different machining process can be done inone machine
Since the machining procedure is donecontinuously, the total time to produce isreduced, less time for more production
-
8/7/2019 laser_beam_machining
33/46
-
8/7/2019 laser_beam_machining
34/46
LBM economics(cont.)
Hardening process was replaced by laserhardening.
Cost is saved due to integration of process.
Less reworking because less distortionoccurred when hardening in finalprocessing.
It is beneficial if the production can be
taken in integrated process as switchinghalf-finished product to another station forfinishing will waste time.
-
8/7/2019 laser_beam_machining
35/46
-
8/7/2019 laser_beam_machining
36/46
Perspectives of applications of micro-machining utilizing water jet-guided laser.
- It is accurate, produce small cutting radius- temperature-controlled which no burns on
work piece
- without producing impurities
3D LDM machining such as turning andmilling- controlling different/ many laser in different
angles
Improving laser quality to cut difficult-to-cutmaterials
-
8/7/2019 laser_beam_machining
37/46
Develop the models with no or very fewassumptions to get the real solution of the LBM
problems quantitatively.- optimization of process variables.- consider about beam spot diameter, thermal
conductivity and reflectivity of work piecematerial
Hybrid or integration of LBM with othermachining methods.
Solve the weakness of laser : thermal process- burns on material hence affect mechanical
properties.- surface is not perfect from aspect ofroughness, parallelism and flatness due toburining.
-
8/7/2019 laser_beam_machining
38/46
-
8/7/2019 laser_beam_machining
39/46
COHERENTCOHERENT
Laser BeamLaser BeamMachining CentreMachining Centre
(LMC)(LMC)
-
8/7/2019 laser_beam_machining
40/46
-
8/7/2019 laser_beam_machining
41/46
Its ApplicationsIts Applications Architectural modelsArchitectural models
PrecisionPrecision ssheet metalsheet metals
Acoustic guitar fabricationAcoustic guitar fabrication
Trophies and awardsTrophies and awards
Medical part fabricationsMedical part fabrications
Printing and nameplatesPrinting and nameplates
Rapid prototypesRapid prototypes
-
8/7/2019 laser_beam_machining
42/46
Extremely reliable ,inexpensive to run ,
provide over 20,000hours of cuttingbefore requiring
service.
Its Laser TechnologyIts Laser Technology
Sealed COSealed CO22 LaserLaser
Compared
to
Flow-through
Gas Lasersrequire an external gas source to
supply gas flowing through the laser
Use onlyUse only100 to100 to
500 Watt500 Wattsealedsealed
CO2CO2
-
8/7/2019 laser_beam_machining
43/46
CombinationCombination of a beam with a low M2of a beam with a low M2
Allowing smaller focus spot
sizes (highly focused spot
(.004 diameter)
Allow square-wave pulsing
characteristics
Allows a 500W model, which
generates 1500W peak power, to
produce instantaneous intensities
of up to 0.3 MW/mm2 at the
material
reduces the Heat Affected
Zone due to lower thermal
conduction
Pulsing gives accurate and
essential control over how
much and how fast energy
is delivered for material
processing by using
dedicated microprocessor
Control to harness
the power of each
pulse and maximize
material processing
efficiency
Less charring when
cutting materials such as
paper, and less melting
when cutting materials
such as polymers.
faster vaporization
of materials, higher
processing speeds
and deeper cuts.
-
8/7/2019 laser_beam_machining
44/46
FarFar--infraredinfraredlight at alight at a
wavelengtwavelength of 10.6h of 10.6microns.microns.
Produce highProduce high--frequencyfrequency
pulses withpulses withextremely fastextremely fast
riserise--andand--fallfalltimes (opposite).times (opposite).
for cutting orfor cutting ordrilling, ratherdrilling, ratherthan for merelythan for merelyheating theheating thematerial to bematerial to beprocessed.processed.
-
8/7/2019 laser_beam_machining
45/46
SlabSlab--discharge CO2 Laserdischarge CO2 Laser VS Conventional CO2Conventional CO2
LaserLaser
Permanentlyconfines thelasing gasmixturebetween two
rectangularplate
Noreplacementgas and noscheduledmaintenance tothe laser headfor up to25,000 hours(roughly two-and-a-halfyears) of
continuousoperation
lowerelectrical andcooling-waterrequirementsthanconventionallasers thatflowconsumablegases throughthe laser head.
Cost
ProductivityProductivity
-
8/7/2019 laser_beam_machining
46/46
from group D