An innovative sensing method for seam tracking based on the arc 'jump sidewall' behavior

To improve the reliability of the arc sensor in the application in the narrow gap welding process, a new method was provided in this paper. The special shape of the signal curve was used in this method to detect the torch deviation. Narrow gap seam tracking experiments showed that the new method displayed better reliability when the deviation was larger than 0.6 mm, and the sensing accuracy can meet the tracking requirements of the narrow gap P-GMAW. The sensing mechanism was studied, and it was found that under conditions of narrow gap and pulse welding mode, the arc 'jump sidewall' behaviour would lead to the change of heat transfer, which will cause the melting of the groove sidewall and the change of the signal curve. The change of the curve was found to be highly sensitive to the groove morphology but was less prone to arc interruption, molten pool disturbance and short circuit. Therefore, the sensing method base on the change of the signal curve exhibits high reliability especially when the arc stability was poor.