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Laser transmission welding (LTW) of polymers is a direct bonding technique which is already used in different
industrial applications sectors such as automobile, microfluidic, electronic and biomedicine. This technique offers
several advantages over conventional methods, especially when a local deposition of energy and minimum thermal
distortions are required. In LTW one of the polymeric materials needs to be transparent to the laser wavelength and the
second part needs to be designed to be absorbed in IR spectrum. This report presents a study of laser weldability of ABS
(acrylonitrile/butadiene/styrene) filled with two different concentrations of carbon nanotubes (0.01% and 0.05% CNTs).
These additives are used as infrared absorbing components in the laser welding process, affecting the thermal and optical
properties of the material and, hence, the final quality of the weld seam.
A tailored laser system has been designed to obtain high quality weld seams with widths between 0.4 and 1.0mm. It
consists of two diode laser bars (50W per bar) coupled into an optical fiber using a non-imaging solution: equalization of
the beam quality factor (M2) in the slow and fast axes by a pair of micro step-mirrors. The beam quality factor has been
analyzed at different laser powers with the aim to guarantee a coupling efficiency to the multimode optical fiber. The
power scaling is carried out by means of multiplexing polarization technique. The analysis of energy balance and beam
quality is performed in two linked steps: first by means ray tracing simulations (ZEMAX®) and second, by validation.
Quality of the weld seams is analyzed in terms of the process parameters (welding speed, laser power and clamping
pressure) by visual and optical microscope inspections. The optimum laser power range for three different welding
speeds is determinate meanwhile the clamping pressure is held constant. Additionally, the corresponding mechanical
shear tests were carried out to analyze the mechanical properties of the weld seams. This work provides a detailed study
concerning the effect of the material microstructure and laser beam quality on the final weld formation and surface
integrity.
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