Process mechanisms based on powder flow spatial distribution in direct metal deposition

Direct Metal Deposition (DMD) is becoming increasingly attention-attracting technology for new component manufacture and repair. However, fundamental process understanding is not yet comprehensive. Without considering the realistic spatial distribution of powder flow, some important process conditions have been neglected in layered deposition, such as the initial stand-off distance of nozzle, scanning direction (orientation of nozzle), change in stand-off distance through process and stability of multi-layer deposition. This then limits the efficacy of deposition strategies which serves to limit the industrial uses of DMD. In this paper, a realistic model was built for the simulation of multi-layer deposition, using real spatial powder flow concentration. Then, the influences of the orientation of nozzle, the stand-off distance of nozzle and single-step rise on geometric characteristics are investigated. It is showed that the stand-off distance of nozzle significantly affects the geometric characteristics of the deposited layer thickness, while the influence of the orientation of four-tip nozzle on deposition can largely be neglected. Furthermore, the stability of multi-layer deposition was discussed, and the steady condition was obtained by analyzing relation among single-step rise, maximum deposited layer thickness and stand-off distance of nozzle. This also allows a deposition strategy to be optimized for the purpose of manufacturing given procedure. The approach taken here is also verified by experiments with the strategies proposed by simulation.