Plastic Welding
with Diode Lasers
June 2005
Laserline GmbH ! Muelheim-Kaerlich ! Germany
www.laserline.de
© Laserline GmbH, Germany
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Characteristics of Diode Laser
Advantages of Diode Lasers
1-step quick-welding
Flexible, any desired welding contour
Non-contact, fluff-free
Easily automated, high process stability
Low thermal and mechanical stress
“Top-Hat”-beam profile w/o intensity peaks
Applications
Gas-/fluid proof containers, electronic/sensor-housings, automotive parts, etc.
Direct diode laser on robot in production. Photo: Toyota
© Laserline GmbH, Germany
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Plastic Welding with Diode Lasers
Joining of Plastics with Diode Laser
" An Industrially Proven Process !
Content
Basics
Types of Welding Processes
Joining Techniques
Examples
Outlook
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Welding of Plastic: Principle
Laser Beam Transmits Top Shell
Laser Beam
F
translucent
Absorption in the Welding Zone
Bottom Shell
Movement
Direction
Melting of Both Parts by Heat Convection
Invisible Weld-Seam
Weld-Seam
No Damage to the Surface
absorptive
F
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Welding of Plastic: Basics
Polymers for Plastic Welding
Thermoplastics (Amorphous or Partially
Crystalline) but not Duroplastics or Elastomeres
Overlapping Melting-Temperature
Comparable Melt Behaviour (Polarity etc.)
Transmission / Absorption Characteristics for
Laser Wavelength: One Transparent, One
Absorbing Layer
Mechanisms of Connection
Intermolecular Forces Between Molecule Chains
Mechanical Attachment by Macro-Molecules That
Diffuse from one Part to the Other
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Main Parameters
Parameters " Welding System
Laser: beam forming, wavelength, optical power,
spot size, energy distribution
Machine concept: laser, manipulating system
(positioning), cooling unit, electrics, other external
components
Parameters " Parts
Combination of thermoplastics (thermal, mechanical
and optical properties " additives!)
Type and positioning of weld seam, thickness, parts
design
Weld Results
Width of the seam
(HAZ)
Optical results
Resulting strength
Internal strains
Parameters " Process
Welding speed, cycle time, absorption of heat /
reaction time
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Welding of Plastic: Basics
Source: VDI Kunststofftechnik/BASF
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Welding of Plastic: Basics
Source: VDI Kunststofftechnik/BASF
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Welding of Plastic: Basics
Laser
F
translucent
Weld Joint
absorptive
“Transmission welding”
Quality of weld depends on:
F
•
Welding pressure
•
Flatness of parts-surface
•
Thickness of transparent welding
partner
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Welding of Plastic: Basics
Typical Part Design with Process Control by Welding Path
Laser
F
„Visible Notch“
„Setting Path“
F
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Plastic Welding: Typical Data
Beam quality [mm mrad]
1000
Här
100
Lö
te n
en
c
e iß
i
w
sstch g
a
o ff
l
t
s
Pnst ldin
Ku
We
ö
H a rtl
S
te n
Au
en
chweiß
Hybrid
Schne
te n
schw
iden
ssc
ftra g
hw e
iß e n
eißen
T ie
f
we
sch
iß e
Power
n
50 W to 800 W
10
10
100
1000
Power [W]
Laser
DioScan, Direct, Fiber-Coupled and
Multi-Diode Lasers
10000
Beam quality
< 150 mm mrad
Spot dimensions
0.5 to 5 mm
Material
- Thermoplaste
Electronics housings
- Thermoplastische Elastomere (TPE)
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Diode Laser Types for Plastic Welding
Direct diode laser, LDL 40
Multi diode laser system (100 diode laser sources)
Fiber-coupled diode laser LDM
DioScan F
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Plastic Welding: Options
DioScan: beam scanner with PC or stand-alone control,
scanner software and integration for plastic welding
Optics with different beam dimensions and working distances
1-inch or 2-inch optics
Ring focus optics for simultaneous welding of circular seams
Circumferential weld optics for welding of tubes
Pyrometer and CCD camera for process monitoring
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Variants of Welding Processes
I. Quasi-Simultaneous Welding (QS):
Uniform, step-by-step heating of the
weld zone
Rotation symmetric parts or any
desired 2D-contour
II. Contour Welding:
One-step-welding process
Any desired geometry, 3D contour
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Special Variants I
Multi-Laser-System:
Rotation symmetric parts
Uniform, simultaneous heating of
different weld zones
Shortest cycle time
Cost reduction due to less process
stations
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Special Variants II
Simultaneous Welding:
Uniform, simultaneous Heating of
the Weld Zone
No internal strains, any part
geometry
Reduced cycle time
Low flexibility, high complexity
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Special Variants III
Scheme: Special Optics
Laser-light-cable
Laser beam
Collimating optics
Circular focusing optics
Special focusing optics for circular focus geometry
„AXICON“
Parabolic mirror
Rotation symmetric part
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Systems Advantages
Weld Geometry \ Laser
Direct & Fiber-Coupled
Scan-System
(QS)
Multi Diode
(simultaneous)
Spot Welds
Contour Welds
Multi-Spot Welds
Step Welds
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I. System Concept: Multi-Laser
Multi-Laser-System
Redundant system
Shortest cycle time
100-Laser-System
Applications
• Structures
• Foils
• Rotation symmetrical parts
Twin-Laser-System
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II. System Concept: QS-Welding
DioScan
Laser safety feature
Simple manipulation system
Laser safety box
Short cycle time
DioScan
Circular table
Application
Sensors, electronic housings,
etc.
Part holder
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Joining Techniques - Comparison
Vibration
Ultrasonic
•
•
•
•
•
•
•
•
1-Step-Process
Mechanical Force Transmission
US-Frequency in Weld Zone
All Thermoplastics
1-Step-Process
Mechanical Force Transmission
Vibration Forces in Weld Zone
All Thermoplastics
Laser
•
•
•
•
1-Step-Process
No Touch
IR-Radiation in Weld Zone
All Thermoplastics (optically suited)
Glueing
• Multi-Step-Process
• Glue Application through Nozzles
• Most Plastics
Heat Plate
• 1-Step-Process
• Global Heating through Heat Plates
• All Thermoplastics
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Joining Techniques - Comparison
Availability
Diode Laser
100
Laser
• Highest welding quality (visible joints, fluff free)
US
VIB
• Highly flexible (robot, axis-system,
Gluing
quasi-simultaneous welding)
• Availability 99.5 %
50
Part damage
• Gap-bridging
Flexibility
0
• Wear-resistant tool
Gap-bridging
Joint-quality
Scan system
Direct diode
laser
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Requirements from Industry
Vibration
Requirements
• Failed parts 0 ppm
• Gap bridging
• Gas proof
• No damage to the part
• No fluff in weld
• Any desired contour
• Sensitive electronic parts
Gluing
Laser
Ultrasonic
Characteristics
• Process control
• Check of melting path
• Endless weld-seams
• Non-contact
• No vibrations
• Maximum flexibility
• Local heat input
Heat Plate
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Weld Seam Geometry YAG vs. Diode Laser
Diode Laser
Nd:YAG Laser
w = weld zone
w
w
Weld seam dimensions. Advantages and
disadvantages of the different systems
Diode
< 0.25 mm.
!-Structures, etc.
Diode Laser
Top-hat beam profile "
Homogeneous weld over
entire width of weld seam
Good weld seam control
Ideal for welds > 0.25 mm
width and larger areas
Nd:YAG
+
+++
0.25 ...1.5 mm
Sensors, small housings, welding with setting
path
+++
++
< 1.5 mm
Large housings, broad area connections,
contour welding
+++
-
Large area welds
Plastic layers, plate material, foils
++
--
© Laserline GmbH, Germany
Nd:YAG Laser
Gauß beam profile:
High central intensity limits
max. power
Higher risk of parts damage
Less homogeneous weld
Ideal for micro structures
< 0.25 mm width
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Influence of Power on Productivity
High flexibility AND
high productivity
5
time(Ges.-Zeit
for weld
Potenziell
[s])
20
scan speed
Polynomisch
(v [m/s])
4
15
3
10
2
5
1
0
0
50
150
250
speed [m/s]
25
total time for weld [s]
Quasi simultaneous welding
Almost constant path
energy without damage
to components
Higher power and scan
speed result in reduced
welding time
influence of laser power, material: PA6,
weld seam length: 250mm
350
laser power [W]
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Scan Software
Laser control by scan software
Graphical view of settings
User-/ Operator surface
Special mode for easy operation
(e. g. operator mode for 3-shift
production)
Contour flexibility, import of dxf, wmf,
bmp, plt, ...
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Prozess Monitoring
Mechanical
Setting path
sensor
Thermal
Pyrometer
Optical
Back reflection
diagnoctics
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Software
Frame-Grabber
Visual
CCD-Camera
Alignment
beam
27
Examples: Automotive Industry
Air Flow Sensor
Car Key
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Schaltbox
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Examples: Automotive Industry
Electronic Housings
Automatic Gear Box
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Plastic Welding: Examples
Mats from plastic material
Invisible weld seam in PMMA
Liquid pouring device
Weld of foam on plastics
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Example: Magnetic Sensor
Photo: Laserquipment
Welding seam
Tyco Electronics AMP GmbH
Integration in a system with round switch table
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Example: Movement Sensor
LDL 40-100 - Direct Diode Laser
Contour Welding
Opaque Material
Source: Laserquipment
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Example: Hydraulic Tank
Welding of hydraulic tanks
DioScan 200
Result:
Excellent welding seam
Single step process
Highest process-stability
Non-contact process
No fluff development
Source: branson
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Example: Ostomy Bags
LDF 600-300
Fiber-Coupled Diode Laser
Medical Industry
Contour welding of concentric
Circles
Soft-to-soft welding
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Example: Filter Element
(1)
Medical Industry
Contour welding of
transparent material
“Clear weld”
(2)
(1)
Black absorbing foil (2)
Source: Leister
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Reference Customers (selection)
Automotive
- Bosch
- Bremi
- Daimler Chrysler
- Geigertechnik
- Grau
- Mendiguren
- Siemens VDO
- VAW
Others
- Boeing
- Colbond
- Erlas
- Philips
- Thyssen
- TRW
Sensors
Metal Welding
Plastic Welding
Electrical-Mechanical
Components
Valves
Housings
Metal Welding
Plastic Welding
Pump-Module for Fiber-Laser
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Outlook
Plastic Welding with Diode Laser
• Highest Quality-Requirement for
Joining Techniques in Automotive
Industry
• Easily Integrated in Full-Automation
Systems
• Customers-Specific Solutions
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