Metal transfer behaviour of CMT-based step-over deposition in fabricating slant features

Abstract

The metal transfer behaviour of slant feature of thin-walls fabricated by cold metal transfer (CMT) process in step-over deposition mode was observed by high speed camera. A slanted short circuiting transfer (SSCT) was generated during deposition and then analysed by asymmetrical magnetic and force model, complicating metal transfer behaviour in comparison with conventional deposition process. The SSCT allowed the droplet to transfer obliquely into the molten pool on previous layer, owing to the pushing force generated by unevenly distributed electromagnetic field in asymmetrical deposition model. The surface tension between wire and liquid metal is the most important force that retarded droplet transfer. The retraction force and electromagnetic force are the main forces to promote droplet transition. The positive forces that promote droplet transfer process can be arranged as Fem > Fr > Fg. The wall width was mainly affected by wire feed speed and the inclined angle can be significantly increased with increasing step-over distance.