Abstract
Directed Plasma Fabrication (DPF) is a rapid tooling process that is based on controlled deposition of molten powder particles according to computer-controlled patterns. It makes fully dense, near net shape metal components without molds or dies, and without forming, pressing or forging systems.
Experimental works were carried out using conventional low current Plasma Transferred Arc Welding system, and metallic powder was stellite #21. Cylindrical shapes are successfully deposited as dimensions with 2.5-4.2mm wall thickness.
The relation between the condition of depositing and the size of molten pool was investigated to make the models accurately as arranged. As compared to thermal conductivity theory, there is considerable effect of some physical factors like arc force on the penetration depth of the molten pool. And as the arc length becomes longer, the molten pool size becomes smaller, as if the heat input were decreased.
To make this phenomenon clear, the reference value of the net heat input, n2, was defined and calculated by using the relation between the heat input and the molten pool length.
As a result of examining the relations between the yield rate of supplied powder and the reference value n2, it was found that by increasing the arc length, the amount of the splashed powder that is not laminated was increased, and that the net heat input by which molten pool was formed was decreased.
