Laser Welding of Transparent Polymers by Using Quasi-simultaneous Beam Off-setting Scanning Technique

Traditionally laser polymer welding has been done by using lasers with wavelength of c. 1 μm wavelength. With this wavelength one of the pair of polymers to be joined needs to be transparent and one absorbing, usually clear and black, respectively. Joining of two transparent polymers with laser has been possible only by using 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 is now possible. In this paper joining of transparent to transparent polymers with quasi-simultaneous laser welding (QSLW) technique and fibre lase with wavelength of 1.94 μm 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 more flexibility on laser welding of polymers is achieved without losing the benefits of quasi-simultaneous laser welding.