Abstract: In order to improve the precision and performance of figuration, the systems of welding robot and high-speed camera video are used to investigate the effects of the behaviors of droplet transition on the figuration of passes-layers in arc rapid prototyping by pulsed gas metal arc welding (P-MIG) with double step. The effects of different transition speeds, droplet sizes and droplet modes on the surface appearances (including surface dimensions, face appearances and side appearances), microstructure and hardness are examined by changing the process parameters including pulse frequency and pulse time. Droplet transition significantly influences the surface appearances, microstructure and hardness of the figuration, especially the mode of droplet transition. The optimal mode of droplet transition for figuration is one droplet per pulse (ODPP). Good surface appearances, uniform integral figuration dimension, homogeneous microstructure and performance, moderate hardness with small fluctuation among layers are obtained with this mode.

Key words: Arc rapid prototyping, Double step, Droplet transition, One droplet per pulse (ODPP)