Diode lasers have become an important tool for polymer welding in automotive industries, in medical and electronics manufacturing. High efficiency and well fitting beam quality make them a perfect tool for industrial applications. With adapted optics it is possible to fit the laser spot shape to the geometry of the work piece. Galvo scanners are the most flexible tool to apply local and precise dose of heat to the work piece. If this flexibility is not needed, the laser spot can be customized by optics to line, circular or arbitrary shaped geometries. For joining transparent parts either an absorbing layer or diode lasers with a wavelength of 1940 nm can be used.