Observation of weld pool profiles in short-circuiting gas metal arc welding

Abstract

Short-circuiting gas metal arc welding (GMAW), a main joining process for light-weight steel structures, is a complex, strongly non-linear, dynamic, and multi input/output process. It is essential to implement real-time monitoring and control of this process in order to ensure product quality and service reliability of the welded structures. In this paper, a low-cost and compact vision system is developed to observe the weld pool surface profiles in short-circuiting GMAW under different levels of welding current, welding speed, and contact tube-to-workpiece distance. Appropriate technical means are employed to lower the arc light interference and to synchronize the image grabber with the short-circuiting stage. Clear and complete weld pool surface images are captured by Observation from the Front of the Pool (OFP) and Observation from the Rear of the Pool (ORP), and the weld pool shape and size are determined. The two viewing methods (OFP and ORP) can detect the pool width reliably, but the detected pool length has a larger error. A modification method is proposed. The weld pool images are captured by Observation from the Side Position (OSP), and the tilted slope of the pool surface and the reinforcement height are detected in this way. Through modification, the measurement accuracy of the pool length is improved. This lays a foundation for the process control of short-circuiting GMAW, but further investigation is still required as a next step.