Additive manufacturing, also known as 3D-printing, is a near-net shape manufacturing approach, delivering part
geometry that can be considerably affected by various process conditions, heat-induced distortions, solidified melt
droplets, partially fused powders, and surface modifications induced by the manufacturing tool motion and processing
strategy. High-repetition rate femtosecond and picosecond laser radiation was utilized to improve surface quality of
metal parts manufactured by laser additive techniques. Different laser scanning approaches were utilized to increase the
ablation efficiency and to reduce the surface roughness while preserving the initial part geometry. We studied post-processing
of 3D-shaped parts made of Nickel- and Titanium-base alloys by utilizing Selective Laser Melting (SLM) and
Laser Metal Deposition (LMD) as additive manufacturing techniques. Process parameters such as the pulse energy, the
number of layers and their spatial separation were varied. Surface processing in several layers was necessary to remove
the excessive material, such as individual powder particles, and to reduce the average surface roughness from asdeposited
22-45 μm to a few microns. Due to the ultrafast laser-processing regime and the small heat-affected zone
induced in materials, this novel integrated manufacturing approach can be used to post-process parts made of thermally
and mechanically sensitive materials, and to attain complex designed shapes with micrometer precision.
Using an in-house developed micro scanner three-dimensional micro components and micro fluidic devices in fused
silica are realized using the ISLE process (in-volume selective laser-induced etching). With the micro scanner system the
potential of high average power femtosecond lasers (P > 100 W) is exploited by the fabrication of components with
micrometer precision at scan speeds of several meters per second. A commercially available galvanometer scanner is
combined with an acousto-optical and/or electro-optical beam deflector and translation stages. For focusing laser
radiation high numerical aperture microscope objectives (NA > 0.3) are used generating a focal volume of a few cubic micrometers. After laser exposure the materials are chemically wet etched in aqueous solution. The laser-exposed
material is etched whereas the unexposed material remains nearly unchanged. Using the described technique called ISLE the fabrication of three-dimensional micro components, micro holes, cuts and channels is possible with high average power femtosecond lasers resulting in a reduced processing time for exposure. By developing the high speed micro scanner up-scaling of the ISLE process is demonstrated. The fabricated components made out of glass can be applied in various markets like biological and medical diagnostics as well as in micro mechanics.
By using focused ultrashort pulsed laser radiation refractive index modifications are induced in glass in order to generate optical components. The understanding of physically fundamental processes induced by laser radiation is the basis for the systematic control and maximization of the refractive index change for the realization of three-dimensional, optical components for integrated optics like in-volume waveguides. In this paper fundamental processes which are induced by focused laser radiation in the volume of borosilicate glass D263 and fused silica are investigated. The glass materials are structured by laser radiation in the infrared spectral range (λ=1045nm). By using femtosecond laser pulses with high repetition rates (f = 500 kHz), thermal processes like heat accumulation effects are induced leading to heat affected zones and thus waveguide cross sections with dimensions larger than the focal spot. The absorptivity during modification in relation to the applied pulse energy is measured for different repetition rates in both glass materials. Furthermore, the laser induced structural change in the glass matrix by the increase of three- and four-membered ring structures is proved with Raman spectroscopy.
Conference Committee Involvement (4)
High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications IV
10 February 2015 | San Francisco, California, United States
High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications III
4 February 2014 | San Francisco, California, United States
High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications II
5 February 2013 | San Francisco, California, United States
High Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications
25 January 2012 | San Francisco, California, United States
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