Quasi-Simultaneous Laser Welding of Transparent Polymers by Using Beam Off-Setting Scanning Technique

Quasi-simultaneous laser welding (QSLW) of polymers is widely known laser joining technique. Traditionally joining of polymers has been done by using lasers of around 1 µm wavelength. With this wavelength the pair of polymers to be joined needs to be transparent and absorbing, usually clear and black. Joining of two transparent polymers with laser has been possible only by using laser absorbing additive between the samples or by doping the polymer with absorbing additive. During the last years lasers with new wavelengths between 1.4 to 2 µm have been developed. With this wavelength range welding of the transparent polymer to another transparent one without any absorbing additives has become possible. Only few studies of joining transparent polymers with new wavelength lasers are published. In this paper joining of transparent to transparent polymers with QSLW technique and 1.9 µm fibre laser is studied. Also a new scanning technique for QSLW is introduced. In this technique laser beam path is off-setting to a different place in every scanning round. This way the Gaussian beam shape of fibre laser can be smoothened to be more suitable for polymer welding and variation of the weld width is possible without changing the scanner optic. With this technique more flexibility on laser welding of polymers is achieved without losing the benefits of quasi-simultaneous laser welding.