Assessing the effects of solid wire electrode extension (stick out) increase in MIG/MAG welding

Abstract

In conventional MIG/MAG welding process, the root of some of the most frequent problems is related to current variation due to solid wire electrode extension (stick out) alteration. This becomes most relevant in semi-automatic welding procedures, where the welding operator is responsible for holding the torch. Inevitably, the contact tip-to-workpiece distance, and as a result, the stick out length, will oscillate due to operational difficulties, such as complex geometry and out-of-position welding. Since the average current has decisive influence over various weld properties, variations in its values incur in reduction of process and weld regularity, repeatability, robustness and reliability. The present work investigates and quantifies the effects such as current drop and electrode temperature profile based on well-known theoretical–analytical concepts under an application oriented standpoint, so as to scientifically support research and development of modern MIG/MAG welding adaptive systems. Results pointed a higher wire preheating degree in spite of lower current levels when stick out is increased. Experiments showed a weld bead geometrical reduction, which can be avoided through an intelligent system, capable of identifying welding current behavior, electrode voltage fall and electrical resistance curves for process online correction and prevention of possible defects.