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.