Fundamental study on on-line image sensing technology of arc welding – development of in-process quality control technology of arc welding

Abstract

ABSTRACT To achieve both welding productivity and quality, in-process welding quality control technology is required. The authors are developing method to detect welding defects directly during welding by using image sensing technology for production lines. To detect the welding defects directly, observing the welding phenomena just near arc where the base metal is melted and defects should occur is important. Conventionally, high-speed camera with laser external light source was used for observing the welding phenomena just near arc, however the cost is high and the equipment is complex for production lines. In this paper, the observation results and the required time resolution of welding phenomena just near the arc were verified by comparison with two observation method, using only an industrial CMOS camera without using an external light source and using high-speed camera with laser light source. By comparison with observation result, the welding phenomena just near the arc could be observed by using only CMOS camera from backside when the molten pool flowed under the arc. And the required time resolution for observation of the phenomena just near the arc were as follows: fluctuation of the arc: over 100 Hz, fluctuation of the molten pool: over 60 Hz, droplet transfer: over 600 Hz.