HPDL-Rofin.ppt

ROFIN MACRO CD 3 - HPDL - 11/04 No.1
The
power
of
light
ROFIN high-power diode lasers

The
power
of
light
Basics about diode lasers

The
power
of
light
Basic diode laser technology
Scheme of a light emitting diode resp. diode laser
Source: B.R.Marx,
Laser Focus World
Sept. 1998. p.104
"slow axis"
(10°-20°)
p-doped
pn-transition
n-doped
-
-
- -
-
-
- - -
Output power: ~ mW
"fast
axis"
(70°-90°)

The
power
of
light
Monolithic integration: The diode laser bar
Sub-array with
ca. 20 –25 emitters
V-Grooves
Mirror-
Facette
1 - 2 µm

The
power
of
light
Intensity distribution
115 µm
ca. 70° x 10°
Typical near-field distribution
Laser diode bars in a gel pack (DILAS)
Typical far-field distribution
Slow axis Fast axis

The
power
of
light
Micro-channel heat sink
Popt
PQ
solder
Pges = Popt + PQ
Popt / Pges > 0.3 - 0.5
Heat resistance:
Rges = RKd + RKv + RKp
RKd = conductive heat resistance:
heat source - coolant interface
RKv = convective heat resistance:
coolant interface - coolant
RKp = capacitive heat resistance::
Heating of coolant

The
power
of
light
Collimation methods
Fast-Axis-Collimation
heat sink
diode bar
FAC lens
Slow-Axis-Collimation
SAC lens array
heat sink
diode bar

The
power
of
light
Poor focusability
"low brilliance"
Stacking
Stacking
• Power of diode lasers is
almost unlimited
• Light is emitted from an area
• Light is emitted from
incoherent sources

The
power
of
light
Spatial coupling
stack 1 stack 2
stack 3
stack 1
stack 2
stack 3
micro-optics
prism stack
for stack 3
prism stack
for stack 2
setup of stacks
(top view)
emitting lines
before and after
combination
- losses at bending prisms (stripe mirrors)
aperture underfill!

The
power
of
light
Polarization coupling
l/2-plate
Micro-Optics
(FAC, SAC)
Heat sink
with laser bar
Glan-Tailor
Prism

The
power
of
light
Wavelength coupling
heat
sink
heat
sink
heat
sink diode laser
bar l3
micro
optics
notch filter
T for l1, R for l2
notch filter
T for l1&l2, R for l3
l1 l1&l2 l1&l2&l3
diode laser bar l2
diode laser bar l1

The
power
of
light
Beam compression
stack prisms
fast
axis
slow
axis
no effect
BPPbefore = BPPafter
dafter
qafter = qbefore •
dbefore
dafter
qbefore
qafter
dbefore

The
power
of
light
The difference to conventional method of power increase
• Elongation / coupling of resonators
• Oscillator-Amplifier set-up
"conventional"
lasers
"coherent coupling"
High-power
diode laser

• Bar / stack
• "side by side"
"incoherent coupling"

The
power
of
light
HPDL
Beam profile
CO2-Slab
DP-YAG (Fiber)
Comparison of HPDL with CO2 and NdYAG Laser
Laser power in W
10.000
1.000
100
0.1
10
100
1.000
Beam-Parameter-Product
*)
1
(θ
0
x
w
0
)
in
mm
mrad
CO2 Laser
Diode-SSL
Lamp-SSL
Disc laser
*) Values at 1/e²
Beam quality
HPDL
Wavelength
0,1 1 10
0,3 3
0,7 7 [µm]
0,8...1 µm 1,06 µm 10,6 µm
UV VIS IR

The
power
of
light
ROFIN high-power diode laser products
beam propagation
Fibre coupled HPDL
Direct HPDL
Defocusing is not recommended for high-power diode lasers!
f
f-1,5
f+1,5
f
f-2,0
f+2,0

The
power
of
light
measurement of beam size: 1/e² vs. FWHM
Focal length f = 100 mm
Power P = 1,5 kW
dfx
dfy
FWHM
86%
2,42
1,78
1,26
0,65
BPPx
< I >
BPPy
mm
mm
mm mrad
mm mrad
W / cm²
FWHM 86 %
0,65
1,78
85
130
1.8x105
1,26
2,42
165
180
4.9x104
Source: DILAS

The
power
of
light
comparison of beam quality with other materials processing lasers
laser power in W
10.000
1 10 100 1.000
0.1
1
10
100
1.000
beam
parameter
product
(
q
0
x
w
0
)
in
mm
x
mrad
CO2 laser
solid-state laser
lamp-pumped
diode-pumped
disc laser
incoherent limit
Source: after P.Loosen, Fraunhofer Institute for Laser Technology, Aachen, Germany

The
power
of
light
1 10 100 1.000 10.000
Laser Power [W]
0.1
1
10
100
1.000
Beam
parameter
product
(
Q
0
*
w
0
)
[mm
mrad]
ROFIN high-power diode laser applications
typical application areas
After P.Loosen, Fraunhofer-Institut für Lasertechnik
Brazing
Hardening
Remelting
Cladding
Cutting
Deep
Penetration
Welding
Limit of todays
diode lasers

The
power
of
light
High power diode laser systems

The
power
of
light
ROFIN high-power diode laser products:
The new DL-Q series
Note: All values
specified at 1/e²
LASERHEAD
CONTROLLER &
POWER SUPPLIES
CHILLER
Power:
700 W – 3100 W
Min. Spot size
0.8 x 1.3 mm²
Shortest focal length
f = 66 mm;
Working Distance
WD = 42 mm ( f=66 mm)

The
power
of
light
comparison with conventional lasers
• large (1 - 3 m³)
• heavy 1000-3000 kg
• high energy consumption (efficiency 3 - 10 %)
• high running costs
 compact (0.02 m³)
 light (25 kg + 75 kg + 150 kg)
 efficient (25 - 40 %)
 1/10 of running costs possible
 beam quality low
High-Power Diode Laser (example 2 kW)
State-of-the-art Laser (example 2 kW)

The
power
of
light
The new ROFIN DL-QSeries (DL x70 Q, DL 014 Q)
slow
axis
spatial
coupling
polari-
zation
coupling
beam-
symmetri
-zation
beam
compres-
sion
fges = 66 mm
Spot size 0.8 x 1.3 mm²
W.D. 42 mm
Accessories:
 Alternative optics (interchangeable tubus)
• f=99 mm, 1.2 x 2.0 @ 73 [mm]
• f=165 mm, 2.0 x 3.3 @135 [mm]
 Green pointing laser
 Fiber coupling
• 1.5 mm diam.; 0,35 NA
 On-axis pyrometer
 Cross-Jet
Working optics
DL-Q

The
power
of
light
The new ROFIN DL-Q Series (DL 021 Q, DL 028 Q, DL 031 Q)
slow
axis
spatial
coupling
polari-
zation
coupling
wave-
length
coupling
beam-
symmetri
-zation
beam
compres-
sion
fges = 66 mm
Spot size 0.8 x 1.3 mm²
W.D. 42 mm
Accessories:
 Alternative optics (interchangeable tubus)
• f=99 mm, 1.2 x 2.0 @ 73 [mm]
• f=165 mm, 2.0 x 3.3 @135 [mm]
 Green pointing laser
 Fiber coupling
• 1.5 mm diam.; 0.35 NA
 On-axis pyrometer
 Cross-Jet
Working optics
DL-Q

The
power
of
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The new ROFIN DL-Q Series (DL x70 Q, DL 014 Q, DL 021 Q, DL 028 Q, DL 031 Q)
40
180
100
220
340
30
3 x M6
62,5
555
430
35
3/4"
DL-Q

The
power
of
light
The new ROFIN DL-Q Series: Controller & power supply
600
0
0
98
948
978
ca.
1250
800

The
power
of
light
The new ROFIN DL-Q Series: Chiller
800
600
978
98
948

The
power
of
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The new ROFIN DL-Q Series: new features
• Reduced stress to the individual bars
• Bridging of defect stacks
• Tight stack housings
• Humidity and temperature sensors in stack
• Change of humidity cartridge on site
• Temperature sensors at all critical components
• IP- and DIN standards
• One connector for all lines and signals
• Improved cooling of working optics
• Simplified cover glass holder (bayonet)
• Power meter (in Watts)
• New power supplies (70 A / 110 W)
• Ramp and pulse form generator
• Cooling circuit sensors: flow, temperature, conductivity, water level
• Several interfaces: analog, CAN-bus, modem
• Touch screen
• Green pointing laser

The
power
of
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Applications: Brazing

The
power
of
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Laser: HPDL with fiber Material: Zinc coated steel Thickness: 1.0 mm
Laser power: 2.0 kW Solder: CuSi3 Wire diam.: 1.6 mm
Speed: 3.6 m / min
brazing

The
power
of
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Applications: Cladding

The
power
of
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cladding: Characteristic process data
Advantages:
• high precision
• process control
• thickness from 0,1 mm to several mm
• large variety of materials
• low heat load
• only little distortion
Characteristic process data:
• power density ~ 104 W/cm²
• deposition: ~ 0.5 to 1 mm layer
thickness at a velocity (v) of ~1
m/min
Deposited layer
Laser
Powder feed
HAZ
Intermixing layer
melt pool
base material

The
power
of
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cladding
Diode laser power: 1.4 kW
Spot size: ca. 4 x 2 mm²
Power density ca. 1.5 x 104 W / cm²
Shield / feed gas Argon
Speed: 400 mm/min
Material: Stellite F Powder
X2CrNi 19.1
--> - wear resistant layer deposition
- repair
1 mm
1 mm
Single track
Multiple track
interface
50 µm

The
power
of
light
modular cladding unit for diode laser
Principle of the coaxial
Powder feeding nozzle
Direct coupling of the
cladding nozzle with a
2.5 kW diode laser
IWS
Fraunhofer Institut
Werkstoff- und
Strahltechnik
By courtesy of::
Dr. Steffen Nowotny
Fraunhofer-Institut für Werkstoff-
und Strahltechnik, Dresden
Cladding module: nozzle.
adjustment unit and fiber

The
power
of
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Cladding of valves of diesel engines for ships
(BIAS, Bremen, Germany)
Supported by:
Cross section
1mm
• Laser power: 700 W
• Powder: Stellite 6
• Substrate: NIMONIC 80
A
• Feed rate: 13,3 mm/s
• Deposition rate: 3,8 g/min

The
power
of
light
Epitaxial cladding of turbine blades
(E-LMF = Epitaxial Laser Metal Forming)
Source: A.Hoebel, B.Fehrmann, A.Schnell, Power Generation Europe 2003
Repair of a turbine blade
of a SX-turbine with diode
laser (SX = single crystal
super alloy)
Cross section of deposition on
single crystalline turbine blade
ALSTOM GT26 Turbine
(286 MW)

The
power
of
light
High-speed cladding of a shaft
Tampere University of Technology
Source: J.Latokartano et. al., Proc. 2nd Int‘l. Conf. on Lasers in Manufacturing, Munich, June 2003
Tampere University of Technology – laser applications laboratory
5 kW high-power
diode laser
Laser power 4.8 kW
Spot size 21 x 5 mm²
Speed 380 mm/min
Powder feed 106 g/min
Layer thickness 1.5 mm
Powder Stellit 21
Base material Fe52
Process photograph
Coated shaft
Multifeeder-
Nozzle

The
power
of
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High-speed cladding:
Comparison of CO2 laser with diode laser
Tampere University of Technology – laser applications laboratory
Layer thickness in mm
Cladding rate in m²/h
Eff. Cladding rate in kg/h
Heat affected zone in mm
Cladding rate in kg/h
Powder efficiency in %
CO2 laser Diode laser
0.5 1.5 0.5 1.5
0.23
6.4
62
3.97
2.3-3.4
1.9-2.6
1.1-1.7
0.9-1.4
0.44
44
1.0
0.075 0.042 0.30
4.7
44
2.07
0.72
38
1.9
Laser power in kW 4.7 4.8
Deposition rate of HPDL 4.7 to 5.5 times faster!!
Source: J.Latokartano et. al., Proc. 2nd Int‘l. Conf. on Lasers in Manufacturing, Munich, June 2003

The
power
of
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why HPDL for cladding?
Laser cladding:
• local heating
• contact less
• precise layer deposition
• high powder use efficiency
• thin interface layer
• low thermal load
- reduced crack formation
- little distortion
• single crystalline cladding possible
Diode laser:
• high efficiency
• favorable wavelength
• moderate investment costs
• low running costs
• compact system
• simple beam guiding
• easy to integrate
• easy to control

The
power
of
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Applications: Hardening

The
power
of
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Hardening with lasers: Process sequence
• Irradiation of the work piece with laser radiation
- Absorption
• Transformation of the absorbed laser power into heat
- local heating of a thin surface layer
• Expansion of the heat front into the material
- Short time local heating above the Austenitisation temperature just below
the melting point (typ. 5 x 102 K/s < dT/dt < 1,5 x 105 K/s)
• Keeping constant temperature for a short time (if necessary) (typ. 10-3 to 10 s)
- Homogeneization of the carbon distribution
- Expansion of the Austenitsation area into the work piece
• Switch off of the laser (irradiation end by movement of the laser spot resp.)
• Self-quenching as a consequence of the fast heat conduction into the work
piece
- no additional cooling medium necessary
• „Freezing“ of the martensitic structure

The
power
of
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Hardening velocity in mm/min
Maximum
hardening
depth
in
mm
Rectangular beam (4:1)
Steel 42CrMo4
Tmax = Tsol – 100K
Max. Hardening depth as a function of velocity
Modeling with GeOpt program of Fraunhofer IWS

The
power
of
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Focus shape square
Absorption 70%
Hardening depth > 0,8 mm
max. Temp. Tsol-100K
Speed v=250mm/min
Laser power / kW
90 MnCrV8
GG 30
42CrMo4
C45
C70
Parameter field for a square beam
Source: 2. HLDL - Workshop Dresden
Max.
hardening
width
in
mm

The
power
of
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Parameter field for optimal beam shape
Source: 2. HLDL - Workshop Dresden
Laser power in kW
Optimal aspect ratio of the beam axes
Maximum
hardening
width
in
mm beam shaping
beam shaping
with without

The
power
of
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Hardening profile (1)
Spot hardening
Material C45
Laser power and temperature
Processing time in s
Cross section
Hardening profile
Hardening depth in mm
Hardness
HV0,05

The
power
of
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Hardening profile (2)
Line hardening
Material C45
Diode laser:
Power 1,35 kW
Spot 6,6 x 6,1 mm²
Speed 700 mm / min
Hardening depth 1,1 mm
Hardening width 5,5 mm
Micro
Hardness
HV0,05
Depth in mm

The
power
of
light
hardening of side cutting pliers
A-B 1 mm
C
D
10 mm
C-D
B 10 mm
A
Diode laser power: 600 W
Spot size: ca. 4 x 2 mm²
Power density ca. 1.5 x 104 W / cm²
Shield gas Nitrogen
Hardening Speed: 120 mm/min
Material: Ck45
• no distortion
• simultaneous welding of both wedges

The
power
of
light
hardening of torsion springs
Torsion Springs
Scheme of hardening setup
Hardness > 800HV0,1
0,2...0,4mm
10mm
170°
Hardening requirements
Process setup
Cross Section
10mm
2mm
-90° +90°
0°
8mm
Process Photograph

The
power
of
light
Hardening of an example part
different geometries in one clamping
spot hardening
360° spiral groove
straight line
Hardened zones
(cross section)
Material: 42CrMo4
Laser power 1500 W
Hardening width: 5 mm
Surface hardness 60 HRc
Hardening depth 0.5 mm (Spiral groove)
resp. full hardening
Cycle time 25 s
No re-clamping necessary!!
ALOtec Dresden

The
power
of
light
High-speed rotation hardening of shafts
5 mm
Cross section
• High turning speed of the shaft (typ. 8-11.000 rot./min)
• „Quasi stationary“ annular shaped heating
• "Glowing ring" is moved in the axial direction
• Fast process control necessary
• Limitation by continuous heat load
• Max shaft diameter about 20 mm
LASER
radial axial

The
power
of
light
Active control of laser power for constant
temperature
Power
supply
Diode
laser
Personal
Computer
Pyro-
meter
Sample
A/D
D/A
Sample part
control loop
Setup with external pyrometer
Actual laser power
Laser
power
/W
620
600
580
560
540
520
500
480
0 20 40 60 80 100
Process time in s
Funded by:

The
power
of
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Why HPDL for Hardening?
Laser hardening:
• local heating
• contact less
• low distortion
• self quenching
• high surface hardness
• high process stability
• good reproducibility
• good controllable
- temperature measurement
- power control
• flexible
Diode laser:
• high efficiency
• favorable wavelength
- no coating required
• rectangular beam profile
• moderate investment cost
• low running costs
• compact systems
• simple beam guiding
• easy to integrate
• easy to control

The
power
of
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Applications: Laser assisted machining

The
power
of
light
laser assisted machining (turning)
Diode laser power: 600 W, integrated into a high precision turning machine
Machined material: Si3N4
• Turning of hard and brittle materials possible
• CNC-controlled
• Complex contours

The
power
of
light
laser assisted machining; controlled metal build-up
F
r
a
u
n
h
o
f
e
r
I
n
s
t
i
t
u
t
P
r
o
d
u
k
t
i
o
n
s
t
e
c
h
n
o
l
o
g
i
e
I
P
T
Injection moulding tool
with moulded parts
Experimental setup at Fraunhofer
IPT (Aachen, Germany) with a
ROFIN DL015S diode laser
Process principle:
1) layer-by layer deposition
from wire (diode laser weld)
2) surface and contour milling
laser beam
inert gas
base material
wire feed
contour milling
surface
milling

The
power
of
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Applications: Welding

The
power
of
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metal welding: dependence of welding speed from power and spot size
• Penetration depth increases
with increasing power density
• Smooth and plane surface
• Lens-shaped weld cross
section at high speeds, half
circle shaped at lower speed
• Plasma plume observed at
power density of 1.7 kW / mm²
at lower speed; depth-to-width
ratio < 1
By courtesy of
Prof. Dr. Berndt Brenner
and Dr.Steffen Bonss
7
6
5
4
3
2
1
0
100 1000 10000
feed rate in mm/min
Penetration
depth
in
mm
0.5 kW, 2.3 x 4 mm²  54 W / mm²
1.0 kW, 2.3 x 4 mm²  108 W / mm²
1.5 kW, 2.3 x 4 mm²  163 W / mm²
2.0 kW, 1.8 x 3.8 mm²  292 W / mm²
2.5 kW, 1.8 x 3.8 mm²  365 W / mm²
2.5 kW, 1.2 x 1.2 mm  1700 W / mm²
Material: mild steel, Thickness: 10 mm, bead-on-plate weld

The
power
of
light
metal welding: dependence of welding depth from material
By courtesy of
and Dr.Steffen Bonss
Bead-on-plate welding
0
1
2
3
Welding
depth
in
mm
X5CrNi18.10
TStE-355
AlCuMg1
Ti6Al4V
AlMg3
Laser power: 2.5 kW
Spot size: 1.8 x 3.8 mm²
Thickness: 6 mm
Feed rate in mm/min
100 1000 10000
• Strong influence of material on
- weld depth
- melt pool geometry
- sensitivity to feed rate
• Main parameters are
- absorption (surface!)
- melt temperature
- heat conduction
- heat capacity

The
power
of
light
metal welding: dependence from weld material thickness
By courtesy of
and Dr. Steffen Bonss
Mild steel, bead-on-plate (6 mm)
Mild steel, full penetration
Stainless steel, bead-on-plate (6 mm)
Stainless steel, full penetration
AlMgSi1, bead-on-plate (6 mm)
AlMgSi1, full penetration
HPDL, power: 1.5 kW
spot size: 2.3 x 3.8 mm²
feed rate in mm/min
0
1
2
3
100 1000 10000
Penetration
depth
in
mm
• Reduced heat flow in thin
sheets causes fast heating
• Much stronger effect than in
case of keyhole welding
• Considerable increase of
welding speed possible!!

The
power
of
light
welding of steel boxes
Diode laser power: 1800 W
Spot size: ca. 3.8 x 1.8 mm²
Power density ca. 2 x 104 W / cm²
Shield gas Argon
Welding Speed: 1000 mm/min
Material: mild steel
Gap bridging!!

The
power
of
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cosmetic weld to avoid crevice corrosion
Diode laser power: 1.45 kW
Spot size: ca. 3.8 x 1.8 mm²
Power density ca. 2 x 104 W / cm²
Shield gas Nitrogen
Welding Speed: 2000 mm/min
Material: X5CrNi18 10
• Gas tight
• Edge smoothened
• Cosmetic weld
before
welding
after
welding
500 µm
500 µm

The
power
of
light
"cosmetic" weld of kitchen sinks
Weld seam before polishing
d1
r
D
a
d2
D
Advantages of laser weld method:
• Reproducible welds
• "Shiny" seam by use of a special gas protection nozzle
• reduced amount of finishing: no grinding - just polishing
Advantages of diode laser (vs. Nd:YAG)
• lower investment
• lower running costs
• higher up-time
• more simple integration
Laser head on robot arm
Cross section of weld seam
d1 = d2 =1 mm

The
power
of
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welding of tubes
Stainless Steel 0.2 mm 20 m/min
Aluminum 0.5 mm 8 m/min
2.8 kW, 0,8 x 1.3 mm²,
BPP: 150 x 180 [µm rad]

The
power
of
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welding of sinter sieves
By courtesy of
Dr. Steffen Bonss
• Laser: ROFIN DL025S
• Power: 2500 W
• Spot size: 1.2 x 1.2 mm²
• Material: Stainless steel
• Thickness: 2 mm
• Weld speed: 600 mm/min
 Narrow seam
 No damage of the sinter sieves
 No spatter
 No polishing necessary
sintered
sieve
weld seam
heat affected
zone
Perforated sheet metal

The
power
of
light
simultaneous welding of gear change forks
By courtesy of
Dr.Steffen Bonss
Experimental set-up for simultaneous welding
simultaneous welded gear fork
• Laser: 2 x ROFIN DL025S
• Power: 2 x 2500 W
• Spot size: 2.4 x 2.4 mm²
• Material: mild steel + AlSi1036
• Weld speed: 1 m/min
 Minimized distortion by sim. weld
 Fine punched parts not required (as
for CO2) – gap bridging!
 Higher speed that MAG
 No spatters

HPDL-Rofin.ppt

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