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Fiber Laser Cutting and Welding at“Extreme Power – Extreme Speed”
ByCharles Caristan – Air Liquide
Jay Finn – Automatic Feed
ICALEO 2009 ConferenceOrlando, FL
• Why “Extreme Speed Extreme Power” Laser Processing?
• Enablers for Extreme Speed Extreme Power
– Fiber laser technology advantages over CO2 lasers for nicheaplications
– Bifocal technology for laser cutting
– Oblong spot technology for laser welding
– New material for freeform focusing lens
• Computational Model vs. Measurements of Caustics
• Experimental Results
• Example of Niche Application: High Speed Laser Blanking
TOC
Why Extreme Speed Extreme PowerLaser Processing?
Volumes of opportunities for industrial lasers in highvolume production - current usage indices in N-A vs. W-C
Degree of Difficulty toImplement in HighVolume Production
Added-Value
High
Low
HighLow
CuttingN-A: 1W-C: 5
weldingN-A: 4
W-C: 13
drillingN-A: 1W-C: 3
MarkingN-A: 16W-C: 20
N-A = North-AmericaW-C = World-class
claddingN-A: 1W-C: 7
In high volume applications, traditional metal processing hasseveral advantages: throughput and piece cost
To overcome these advantages, laser processing must operate atincreasingly high speeds and make the case for piece costwithout sacrificing quality.
Opportunities & Challenges
“Extreme”Quadrant
Example: Fiber Laser-Cutting of High Strength SteelPower versus Speed
Laser-processing at speeds above 20 m / min andpower exceeding 4kW are in the “extreme quadrant”
Dual focus technology for laser cutting
Oblong spot technology for laser welding
Fiber lasers are twice as energy efficient as CO2 lasers; they donot require periodic mirror cleaning and alignment downtimes
Niche high volume applications: thin gage cutting and welding
Different optics material and designs
Enablers for Extreme Power Extreme Speed
Bifocal technology for
laser cutting
Industrialized Methods for Dual Focus Effect
Enhanced Focus Position Tolerance Dz
Cu
ttin
gS
pee
d(i
nch
/m
in)
Focus Position (inch / 1000)
Bifocal technology to boost “production” cutting speedand increase R&R with larger focus position tolerance
Oblong spot technology for
laser welding
13
With appropriate mirrors A and B, the focused beam spot on theworkpiece can be oblong L x W, with the longitudinal length Loriented parallel to the welding direction.
If Mirror A is a standard flat mirror and mirror B a standardparabolic mirror, then the focused beam spot on the workpiece iscircular of diameter W W
W
y
zx
L
W
y
zx
Welding Directiony
z
x
Welding Directiony
z
x
HSHP Laser Welding with an Oblong Focused Spot
Laser welded with an oblongfocused beam spot
14
W
n x P- Laser with power n x P- Focus spot circular of diameter W- Welding speed n x V
B
L= n x W
W
n x P- Laser with power n x P- Focus spot oblong L x W- Welding speed n x V
C
High Speed High Power Case Comparison (time t = 0
Thin slice of workpiece
being laser-welded
- Laser with power P- Focus spot circular diameter W- Welding speed V
W
PA
15
High Speed High Power Case Comparison (time t = W / V)
Thin slice of workpiece
being laser-welded
- Laser power P / Welding speed V- Average power density P / W2
- Irradiation time W / VA
B
C
Cases A&C: low
Cases B: high
power density
long
short
irradiation time
LOW
HIGH
WELD DEFECT RATE
- Laser power n x P / Welding speed n x V- Average power density n x P / W2
- Irradiation time: W / (n x V)
- Laser power n x P / Welding speed n x V- Average power density P / W2
- Irradiation time: W / V
The workpiece does not distinguish between cases A and C
New material for freeform focusinglens
Conduction coolingof lens flange
Modepower distribution
Temperature gradient profilevaries between cold and hotmode operation and inducesfocus shift
Focusing Lens
focus shift
Incident beam diameter
Transmissive Optics’ Materials for Fiber LaserProcessing at “Extreme Speed Extreme Power”
ZnS Material for Transmissive Optics for Fiber LaserProcessing at “Extreme Speed Extreme Power”
Transmissive Optics’ Forms for Fiber Laser Processing
Beam Propagation Caustics Measurements
Bifocal lens Standard lens Toroidal lens
Beam Caustics
Computation vs. Measurements
2
12
outout 1(z)W
R
out
Z
dzw
24
4222
22
24
4222
2
2
24
4222
24
42
;;
M
w
ww
M
wM
w
Z
M
wM
w
din
inout
in
in
R
in
in
out
Beam Propagation Caustics Calculation
Beam Propagation through a Toroidal Focusing Lens:Measurements vs. Computations
Bead-on-Plate 5kW Fiber Laser-Welding in 1.5 mmAdvanced Strength Steel
Beam Propagation through a Bifocal and StandardFocusing Lens: Measurements vs. Computations
Dross-free cut edge quality of high strength steel atextreme power extreme speed
Niche application
High speed laser blanking
28
From Manufacturing ….To Laserfacturing
OLD
NEW
Multiple Lasers for Throughput
Optimum Nesting for Material Utilization
Nested for die-blanking Nested for laser-blanking
49.89% Material Utilization 65.90%
Unit Die 1-laser 5-laser
Volume per year 300000 300000 300000Production Speed part/min 30 5 25
Throughput part/min 16.6 3.4 14.8Blanking Die Cost $ K 100.0 none none
System Cost $ MM 7.0 3.5 9.5
Blanking System $ / part 0.32 0.67 0.45Blanking Die $ / part 0.08 0.00 0.00
Variable Costs $ / part 0.07 0.35 0.14Material Costs $ / part 2.74 1.77 1.77Scrap Reclaim $ / part (0.73) (0.37) (0.37)
Total Piece Cost $ / part 2.49 2.41 1.98
Piece Cost(incl. MRO)
Blanking System
Production
Throughput and Piece Cost Comparison
Conclusion• The technological and commercial developments of fiber lasers enable
today the use of 5kW and above fiber lasers for “Extreme SpeedExtreme Power “ laser processing for certain niche high volumeproduction applications.
• This paper starts the validation process for a new ZnS material fortransmissive lenses that enables better control of thermal lensing.
• This new material also enables freeform optics such as toroidal lensesfor welding with an oblong focused beam spot and bifocal focusinglenses for laser-cutting. Both methods enhance speed and quality.