Laser beam micro welding in the watch industry

After the invention of the laser principle and its first application for drilling of jewels in watch movements, the laser was only used for marking. The still ongoing trend of miniaturization and automation opened a new field of application: laser beam micro welding. This paper gives an overview of the new application of laser beam welding in the watch industry. The combination of dissimilar materials like brass and stainless steel is often needed in watch movements due to tribological aspects. Here, laser beam micro welding offers an alternative to conventional joining techniques like press fit or gluing. Since the watch components are very small, the locally limited heat input of the laser beam offers the possibility of weld seam widths <200 mu m. The depth and the width of the closed weld seam and the surface quality can be influenced, especially at the end of the seam, using the pulse forming capability of a pulsed Nd:YAG laser. Several watch components could be joined by means of laser beam micro welding. The width of the seam could be reduced to 100-200 mu m. The joining geometries of an axis/wheel combination are in the range of 100 mu m to 1 mm diameter of the axis and about 200 mu m wheel thickness. The process of laser beam micro welding could be integrated in a fully automated assembly machine for watch movement parts. This paper gives an overview of some results of a European research project where the welding of microparts was investigated. The aim was to decrease contamination and distortion of the parts during the welding process.