Particle size segregation promoted by powder flow in confined space: The die filling process case

Tablet compression has great significance in the pharmaceutical industry since most of the drugs are in the tablet dosage form. The tablet press feed frame is used to fill powder into the empty dies. Die filling is one of the key steps to control final properties of tablets. Using the Discrete Element Method (DEM), a standard feed frame taken from a Manesty Betapress was simulated which represents the tableting process without the compression stage. DEM was used to understand the micro-macro dynamics of the particles inside the feed frame. Segregation behavior of a single material with a particle size distribution was investigated using this method. The DEM simulation components included 2 paddle wheel speeds (24 and 72 rpm) and 2 die disk speeds (29 and 57 rpm). Results obtained have highlighted the effect of feed frames on the powder properties. The DEM results show size segregation inside the feed frame and during the die filling stage. Velocity profiles and particle vectors show that the percolation phenomenon is the most significant segregation mechanism. Paddle wheel speed was demonstrated to be the most important factor to control particle size segregation inside the feed frame. (C) 2014 Elsevier B.V. All rights reserved.