Modelling and thermal simulation of absorber-free quasi-simultaneous laser welding of transparent plastics
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RESEARCH PAPER
Modelling and thermal simulation of absorber-free quasi-simultaneous laser welding of transparent plastics Nam-Phong Nguyen 1
&
Stefan Behrens 1 & Maximilian Brosda 1 & Alexander Olowinsky 1 & Arnold Gillner 2
Received: 9 December 2019 / Accepted: 23 July 2020 # The Author(s) 2020
Abstract The growing demands on the quality of plastic components and the trend towards miniaturisation are posing a great challenge on plastics processing technology. As many complex components can no longer be manufactured in a single step, joining processes such as laser transmission welding are gaining in importance. In classic laser transmission welding, the joining partners have different optical properties. The upper joining partner is transparent in the laser wavelength range, whilst the lower partner is absorbent due to the addition of absorber materials. In medical and biotechnological applications, the addition of absorber materials is often undesirable due to strict biocompatibility requirements. If, on the other hand, radiation sources are used which emit radiation in the area of the natural absorption of the plastic (λ = 1600–2000 nm), untreated transparent plastics can also be welded. In this work, a theoretical model will be presented to calculate the temperature distribution and progression during quasi-simultaneous welding using a thulium fibre laser (λ = 1940 nm). A sensitivity analysis is carried out to investigate the influence of different parameters on the heat affected zone (HAZ). The simulated HAZ is then compared with the HAZ from the experimental work. Keywords Plastic joining . Transparent polymers . Thermal simulation . Laser transmission welding
1 Introduction The growing demands on the quality of plastic components and the trend towards miniaturisation are posing a great challenge on plastics processing technology. As many complex components can no longer be manufactured in a single step, joining processes such as laser transmission welding are gaining in importance [1]. For example, microfluidic components such as lab-on-a-chip devices combine the functionalities of analytical instruments in a small chip. The higher portability allows these tests to be performed on site. The challenge here is the media-tight encapsulation of the narrow and complex channel structures with channel diameters less than 300 μm. Recommended for publication by Commission XVI - Polymer Joining and Adhesive Technology * Nam-Phong Nguyen [email protected] 1
Fraunhofer Institute for Laser Technology ILT, Steinbachstr. 15, 52074 Aachen, Germany
2
Chair for Laser Technology LLT, Steinbachstr. 15, 52074 Aachen, Germany
One promising approach is laser transmission welding. The temporal and spatial defined and contactless energy input leads to a precise welding process at low thermal and mechanical stress [2, 3]. In classic laser transmission welding, beam sources are used which emit radiation in the transparent wavelength range of most polymers (λ = 800–1100 nm). Therefore, the modification of the opt
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