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WET: 01.06.2016 Dynamic Beam Shaping

Dynamic beam shaping for high power laser applicationsDr. Andreas Wetzig, Dr. Jens Standfuß et al.

Fraunhofer-Institut für Werkstoff- und Strahltechnik Dresden

Source: Goppold, et al., (2016) Transient beam oscillation with a highly dynamic scanner for laser beam fusion cutting, Advanced Optical Technology, January, 13, DOI 10.1515/aot-2015-0059

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Introduction

Fast Galvo Scanners for Beam Shaping

Laser Welding

Laser Cutting

Novel Approaches through MEMS-Scanners

Summary

Dynamic beam shaping for high power laser applications

Outline

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Introduction


http://www.holoor.co.il/Diffractive_optics_Applications/Application_Notes_BeamShapers.htm

Static beam shaping through Diffractive Optical Elements

Sophisticated light distribution possible

http://spie.org/newsroom/5850-diffractive-optics-technologies-further-advance-photonic-systems

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Introduction


Laser Welding

Laser Cutting


Summary


Outline

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Laser heat treatment of turbine blades by means of direct diode lasers1D Galvo Scanner with f = 200 Hz

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Design

Special beam path

Limited beam aperture

Working field size depends on dynamic

Specification

4 kHz beam oscillation in x and y direction

up to 4 kW laser power (solid state laser)

Typical oscillation amplitudes 0.1 – 0.5 mm

Working field: low dynamic 10 mm x 10 mmhigh dynamic 1.5 mm x 1.5 mm

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Software

Fully control of scanner movement and laser power

Processing of feedback signals + adapting of position values = constant oscillation conditions at various frequencies

Independent programming of x and y oscillation

Scanner position related laser power modulation

Lis

sajo

us

-Fig

ure

s

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Introduction


Laser Welding

Laser Cutting


Summary


Outline

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Laser Welding


fScan = 200 Hz fScan = 700 Hz

Vweld / VWIRE = 1

Spot = 210 μm

fscan = 350 Hz

505

ca. 27 m

m

596

ca. 25 m

m

up to 1,5 mm up to 3,5 mm

Vweld / VWIRE = 3

Spot = 600 μm

fscan = 100 Hz

Laser-Multi-Pass-Narrow-Gap welding (LMPNG)

Example: hot crack sensitive Al-6082

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Laser Welding


Laser-Multi-Pass-Narrow-Gap welding (LMPNG)

50 m

m

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Laser Welding


Joining of aluminum wrought alloy and die cast

rotation of the beam on an elliptic track

extension of the keyhole

- less pores- less spattering

Extension of melt pool life time

Increasing of degassing time for bubbles

Homogeneous, slow solidification

Die Cast

Al Tube

Die Cast

Al Tube

without Beam Oscillation

with Beam Oscillation

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Laser Welding


Joining of aluminum wrought alloy and die cast

Machine

Optical Set-up

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Introduction


Laser Welding

Laser Cutting


Summary


Outline

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Laser Cutting


Thick plate fusion cutting of stainless steel 1.4301

Al Tube

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Laser Cutting


Thick plate fusion cutting of stainless steel 1.4301

feeddirection

Source: Goppold, et al., Beam oscillation –periodic modification of the geometrical beam properties, LIM Conference 2015


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Laser Cutting


Ro

ug

hn

ess

Rz

Material 1.4301Thickness 12 mmMulti mode fiber laser

Laser power 3 kW; Cutting speed 0.4 m/min Laser power 3 kW; Cutting speed 0.5 m/min


Static laser beam High frequency beam oscillation

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Laser Cutting


CO2 Laser Fiber Laser

Beam Shaping without Beam Shaping without

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Introduction


Laser Welding

Laser Cutting


Summary


Outline

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MEMS-Scanner


Initial idea – MEMS Scanner for display applications

Requirements for high power laser application

Large Apertures 7 mm ... 20 mm High Scan frequencies 1 kHz ... 20 kHz High average laser power 50 W ... 4 kW Scan angles of 0.03 ° up to 5 °

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MEMS-Scanner


Current Status

Usage of open MEMS-Scanner instead of capsuled Tests with IR laser power up to 4 kW Experiments on micro applications (5 kHz, 16 W) Proof of principle for laser fusion cutting

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MEMS-Scanner


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MEMS-Scanner


T43,4 kHz

L = 16 WSG = 1500 mm/sRR = 100 kHzA= 50 mV

T53,4 kHz


T63,4 kHz


T75 kHz


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High dynamic beam shaping opens up new possibilities of laser material processing.

New material combination can be joined by laser welding as well as Laser-Multi-Pass-Narrow-Gap welding can be realized.

Cutting edge quality and speed can be improved at same laser power compared to conventional processing.

Galvanometer based scanners for frequencies up to 4 kHz are available.

Biaxial MEMS scanners have the potential to reach frequencies beyond 4 kHz and to become a valuable complementation of conventional scanning technology.

Summary and Outlook


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Thank you for your attention!

Parts of these works were supported by:

The joint research initiative MabriLAS of the Federal Ministry of Education and Research (BMBF) within the research program "Optical Technology - Made in Germany” (13N10197)

FhG Internal Programs under Grant No. WISA 824 747

Many thanks go to Jan Hauptmann, Patrick Herwig, Cindy Goppold, Thomas Pinder, Achim Mahrle, Dirk Dittrich, Axel Jahn, Berndt Brenner, Ulrich Hofmann, Frank Senger

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