Analysis of Arc Light Mechanism and Its Application in Sensing of Gtaw Process

Sensing plays a key role in automating and controlling welding processes. Although arc light sensing has advantages over through-the-arc sensing for arc length control and seam tracking, the current technology relies on experimental data and lacks theoretical foundation. To improve measurement accuracy, this work addresses the theoretical foundation for arc light sensing. A theoretical model has been developed to correlate arc light radiation to welding parameters. Distributions of different radiant sources in the arc column are studied. It is found that the distributions of the ions of the shielding gas and the vapors of the base metal and tungsten are not even, while that of the shielding gas atoms is. This suggests that the spectral lines associated with the shielding gas atoms can be used to improve the accuracy of arc light sensing. Hence, an arc light sensor has been developed to detect argon atom spectral lines in gas tungsten arc welding. The relationship between the argon lines and the welding parameters has been derived from the theoretical model. Seam tracking examples showed the effectiveness of the developed method in improving the accuracy.