Visual-based spatter detection during high-power disk laser welding

• Based on visual sensing of near infrared, ultraviolet and visible light, spatter detection during laser welding was performed.
• A novel spatter features extraction and quantification were proposed and proved to be effective.
• Experimental results show that there was a close relationship between the spatter feature and the welding quality.

The spatters created during laser welding are considered as essential information for welding quality inspection. This paper proposes a laser welding quality inspection method based on the high-speed visual detection. A high-power (10 kW) disk laser bead-on-plate welding of Type 304 austenitic stainless workpiece was carried out and two high-speed cameras were used to capture the spatter images. The first one was used to measure the near infrared (IR) light emitted from a molten pool, and the second was utilized to measure the ultraviolet (UV) light and visible light. By comparing the images captured from two different cameras, it was found that the measurement of UV light and visible light was more appropriate for spatter detection. Based on image process technology, a novel spatter detection algorithm was presented. A shape similarity function and angle similarity function of the spatters were established for spatter recognition by defining the spatter features, such as centroid position, gray-value, average gray-value and radius. The spatter volume, spatter gray-value and spatter radius were used to evaluate the welding quality. By comparing the spatter information with the molten pool width, this paper investigates the internal relationship between the welding quality and the spatter feature parameters. Experimental results proved that the proposed spatter feature extraction method could guarantee an accurate evaluation on the quality of high-power disk laser welding. In addition it was demonstrated in this study that, by using high-speed visual detection and image processing technology, the quantities and feature of spatters could be measured during the welding process.