Mapping the droplet transfer modes for an ER100S-1 GMAW electrode

Abstract

Welds were made with a 1.2- mm-diameter AWS ER100S-1 electrode using Ar-2% 02 shielding gas to map the effects of contact-tube- to-work distance (13,19 and 25 mm), current, voltage, and wire feed rate on metal transfer. The droplet transfer modes were identified for each map by both the sound of the arc and images from a laser back-lit high­ speed video system. The modes were cor­ related to digital records of the voltage and current fluctuations. The maps con­ tain detailed information on the spray transfer mode, including the boundaries of drop spray, streaming spray and rotat­ ing spray modes. The metal transfer mode boundaries shifted with an increase in contact-tube-to-work distance. Increas­ ing the contact-tube-to-work distance from 13 to 19 mm resulted in a 1 5 mm/s increase in the wire feed rate for the glob- ular-to-drop-spray transition. isting robotic actuators can duplicate the precision of human arm movements in manipulating the electrode along the joint, but substantial improvements are needed in sensor and control system technology. Monitoring of the electrical signals (through-the-arc sensing) is one sensing strategy for an intelligent welding control system. Electrical perturbations related to metal droplet transfer in gas metal arc welding (GMAW) can be used to sense changes in the welding conditions. The control loop would contain rules based on the expertise of a human welder and allow the controller to make the proper responses to the conditions detected by the sensors. A through-the-ar c sensing strategy does not intrude into the arc re­ gion and eliminates sensor-workpiece in­ terference and sensor blinding problems. Although the electrical signals were correlated to arc characteristics as early as 1955 (Ref. 1), recent advances in dig­ ital signal capture and processing tech-