Analytical Modeling of Metal Transfer for GMAW in the Globular Mode

A lumped parameter dynamical model is developed to describe the metal transfer for gas metal arc welding in the globular mode. The oscillations of molten drop are modeled using a mass-spring-damper system with variable mass and spring coefficient. An analytical solution is developed for the variable coefficient system to better understand the effect of various model parameters on the drop oscillations. The effect of welding drop motion on the observed current and voltage signals is investigated, and the model agrees well with the experimental results. Furthermore, the effect of wire feeding rate (or welding current) on the metal transfer cycle time is studied, and the model successfully estimates the cycle times for different wire feeding rates. Possible regions of unstable metal transfer are investigated both by the model and experiments. The model can be used to identify the range of welding wire feed rates that results in stable metal transfer during the globular mode of metal transfer.