Conventional laser transmission welding (LTW) of plastics is an established joining technology with advantages such as precise energy input, flexibility of the seam geometry, and short heating times. The primary factors for the weld seam strength are the temperature during welding and the time the polymer stays in the molten state.

To reduce welding time further into the sub-ms to ms-range, a high-speed laser welding process is being developed that operates at laser powers in the kW range and still achieves suitable weld strengths. In this work, the weldability of polycarbonate and glass fiber reinforced Polyamide 66 is investigated. Therefore, joining by contour welding and simultaneous welding is explored.

For simultaneous welding, a multi-kW diode laser with Top Head generating optics is used. The optical design allows the stepless selection of the area to be irradiated. This allows for further adjustment of the intensity by reducing or increasing the irradiated area.

A beam shaping optic, using a spatial light modulator (SLM) allowing laser powers of a few hundred watts, is set up. Thus, the intensity peak of Gaussian power distribution leading to decomposition in the seam center and the inhomogeneous weld of a top head profile in contour welding is addressed. The beam shaping setup is characterized by measuring the resulting beam characteristics.

The resulting welds are characterized by means of tensile shear tests and microscope images. The weld strength and visible heat affected zone are then compared with the weld strength and visible heat affected zone of conventional welding.