DEM simulation of particle segregation in filling of vibratory dies

Abstract

The homogeneity of the metal powder in the dies is a primary factor affecting the quality of the product obtained by powder metallurgy manufacturing routes. Hence, a desirable goal during die filling is to achieve a homogeneous distribution of particles. However, the presence of particles of different shapes and sizes in metallic powders may give rise to inhomogeneous distribution leading to the segregation of particles. In addition to segregation, the presence of cavities or gaps in the dies with sharp features can affect the quality of final products. In this work, discrete element simulations are carried out to study the die filling of an axisymmetric die with internal stepped features which led to the formation of gaps in the die as it is filled with particles. The die is subjected to vertical vibratory motion and the effect of vibration parameters on the size segregation of particles and the compaction characteristics of the metallic powder are studied. At higher amplitudes, a cluster of coarse particles was observed at the center near the base of the die. At higher vibrational frequencies out of phase, flows were observed in the stepped regions of the die which led to the formation of surface waves.