Molten pool behaviors and forming appearance of robotic GMAW on complex surface with various welding positions

For the robotic GMAW on complex surface, the welding position is various along the welding path at different region, which results in the diverse molten pool behaviors, forming appearance or even the defects. To investigate the molten pool behaviors and forming appearance on the complex surface, the welding pose on the surface was described, the computational fluid dynamics model of the weld pool considering the droplet impingement, gravity, arc force, heat and mass transfer for four typical welding position was developed. The influence of gravity on the fluid flow for different position was investigated, and the results were validated with the high-speed welding camera. The deposition experiments with different welding current and local inclined angle were conducted to analyze the influence of the welding parameters and surface geometrical structure on the forming appearance. The results indicated that the influence of the gravity on the flow field and forming appearance at various welding position was different. The effect increased with the welding current, the surface local inclined angle (??[0, 90?]), and the absolute value of speed angle (|?|?[0, 90?]), which was minimized when the torch travel direction was perpendicular to the gravity (? = 0?), because of the attenuated influence on the backward fluid flow. The findings help explain the molten metal forming mechanism of the welding on complex surface and improve the forming appearance.