Weld Pool Centroid in the Application of Weld Seam Formation Control

Abstract

The weld seam formation is one of the key aspects for welding quality. In this paper, a new method for seam formation control has been proposed, which is based on the weld pool image gray centroid. The tungsten inert gas arc welding is chosen to be the researched welding technology. Firstly, the experimental system, which is four degree of freedom, was set up. The composite filtering system was used to filter the weld arc producing during the welding procession, which is composed by the neutral light reduction filter and narrow band light filter. Nextly, several welding experiments under different penetration conditions were performed. The CCD camera captured the welding images and saved them to the computer. Then the images were processed by median filter and gray enhance operations. So the clearer weld pool images can be obtained. The front region of weld pool is chosen to be the procession district. Some analysis has been performed to the light radiation and heat conduction during the welding procession. On this basis, the weld pool image gray centroid value is chosen to be the parameter reflecting the heat distributed situation during the welding procession. The least square method is used to set up the relationship model between the pool centroid and the welding penetration conditions, which are unfused, fused and overfused. In the end, several experiments were performed to test the veracity of the model. The results showed that the welding penetrations predicted by the set up model are fit to the measured values. The accuracy of the model is 90%. The setup model can predict the weld seam formation effectively.