A STUDY ON AN ARC SENSOR FOR GAS METAL ARC-WELDING OF HORIZONTAL FILLETS

Abstract

The weld joint tracking sensor is indispensable for improving the flexibility of arc welding robot applications. Recently, some sensing methods that utilize the electric arc signal, or more correctly the welding current in GMA welding, have been developed and are prevalently in use. The welding current is directly affected by the contact tip-to-workpiece distance for the given welding voltage and wire feed speed. Armed with a means of measuring the welding current, the tip-to-workpiece distance and then the weld joint geometry can be obtained by weaving the arc back and forth across the line of travel. Knowledge of the weld joint geometry relative to the welding gun permits the welding gun to trace the joint. In this study, the welding current signal was fitted to a curve, which is inversely proportional to the trace of contact tip-to-workpiece distance by using the quadratic curve-fitting method in order to extract useful information on the welding gun position from the welding current signal. Furthermore, the availability of the curve-fitted welding current signal was investigated and a joint tracking system for horizontal fillet joints was developed by using this curve-fitting method.