Visualization of Powder Behavior for Gravity Filling

It is essential for improving the dimensional tolerance of complex P/M parts to uniformly fill powders in a die cavity. This study is aimed at clarifying the powder behavior in filling the die cavity. A visual apparatus was developed for observing the powder behavior. Using this apparatus, the effects of the die cavity shape and feed-shoe speed on the filling behavior, density and particle size segregation of filled powders were investigated for gravity filling of atomized iron powders. It is clarified that the particle size segregation in filling occurs independently of the shoe speed and die cavity shape. Coarse particles segregate in the place where the powder falls along the angle of response, while fine particles segregate in the thin-walled part and the position where the empty space finally disappears.