Hollow core waveguide for simultaneous laser plastic welding

Welding of plastics is a very important process in many industrial fields such as electronic packaging, medical applications, textile joining and automotive. It is often used when finished structure is too large to mold, for cost effectiveness or when dissimilar materials have to be joined. It is also employed in MEMs and Bio-MEMs applications, for example for microfluidic devices, where joint areas are very small, and need an amount of precision that other techniques can't provide. This work focuses on description of transparent laser plastic welding technique, comparing simultaneous and quasi-simultaneous welding, and the development of an experimental setup for an automotive application. There are different laser welding methods, like simultaneous welding, where all the joining interface is irradiated at the same time and often includes a hollow guide to direct laser beam, and quasi-simultaneous welding, for example contour welding or scanning welding, where the laser spot is driven on joining interface via movement of the source or changing the path of the laser beam. An innovative tool end experimental setup was made to evaluate the simultaneous versus quasi-simultaneous welding to join polymeric material for an automotive application. A DFSS design of experiment was used. A LIMO laser bar diode @808nm with a maximum output power of 50 Watts, was coupled to a multi-mode 400 μm glass core optical fiber (Boscottica) with a numerical aperture of 0.22, by a LIMO Beam Transformation System HOC 150/500 (1401.612). The beam at the output of the fiber was guided through two different optical systems to the welding joint to test the two methods. A SANYO stepper motor was used for the quasi-simultaneous welding. Different kind of plastic materials were joined, Hostacom TRC 787N and THERMORUN TT875NE/BE. We performed static pull tests and dynamic pull test, and found optimum and baseline configuration.