A STUDY ON PREDICTION OF WELDING CURRENT IN GAS METAL ARC-WELDING .2. EXPERIMENTAL MODELING OF RELATIONSHIP BETWEEN WELDING CURRENT AND TIP-TO-WORKPIECE DISTANCE AND ITS APPLICATION TO WELD SEAM TRACKING SYSTEM

Abstract

The weld joint tracking sensor is indispensable to improve the flexibility of the arc welding robot application. Recently, some sensing methods that utilize the electric arc signal, or more correctly the welding current in gas metal arc welding (GMAW), have been developed and are prevalently in use. The welding current, however, is directly affected not only by the tip-to-workpiece distance, but also by the welding voltage and wire feed speed. Thus a model that is able to determine the welding current in response to the tip-to-workpiece distance was proposed for the gas metal arc welding process. The model was developed by using the factorial experiment and least-squares method to the variables of welding voltage and wire feed speed. The relationship between welding current and tip-to-workpiece distance determined by the proposed model was compared with the experimental ones and it was revealed that both the results show good agreement within the considerably wide range of welding conditions. The model was used for developing a weld seam tracking system which controls the moving speed of a welding torch in the height direction. It could be shown that there is a successful capability of seam tracking in flat welding of V-groove butt joins. Furthermore, the model can be used for the analysis of the weld pool formation and weld bead geometry, and also for the determination of appropriate process parameters.