While the pinch instability theory (PIT) has been widely employed to analyze the spray transfer mode in
the gas metal arc welding (GMAW), it cannot predict the detaching drop size accurately. The PIT is
modified in this work to increase the accuracy of prediction and to simulate the molten tip geometry to be
more physically acceptable. Since the molten tip becomes a cone shape in the spray mode, the effective
wire diameter is formulated that the effective diameter is inversely proportional to current square.
Modifications are also made to consider the finite length of the liquid column and current leakage through
the arc. While the effective diameter influences drop transfer significantly, the current leakage has negligible
effects. The effects of modifications on drop transfer are analyzed, and the predicted drop diameters show
good agreements with the experimental data of the steel wire.