Vision Systems

A testing method which is already widely used is online-CCD tracking. This is used when there is a strong contrast in the materials being welded – such as opaque/black.

This type of monitoring system can be easily integrated into contour welding methods in particular. The smallest faults in the weld seam can be reliably detected with a suitable evaluation routine. In addition, the monitoring system can analyze the width of the weld seam as well as recording other quality criteria.

A camera system is used to monitor transmission laser welding with the aim of detecting inadequate adhesive bonding along the weld seam. Although the absorbing welding partner usually has a uniform color, it is possible to detect differences in lightness between the joint line and its surroundings. This is because the zones at the welded horizon with proper adhesive bonds have no boundaries between the two welding partners. Because an ideal smooth boundary between a plastic and the surrounding air reflects around 4 per cent of the orthogonal radiation hitting the surface, unwelded zones appear lighter in the camera image.

Although camera systems can also use the laser optics to monitor the process in real time, the images generated in this way have contrast properties which are unfavorable for algorithmic evaluation. Image processing systems operating behind a welding unit are not affected by this problem.