Numerical investigation of segregation behavior of multi-sized particles during pharmaceutical mini-tablet die filling

During pharmaceutical die filling, the quality of the tablet is greatly affected by the uneven distribution of raw powder and the accompanying segregation of multi-sized particles. To improve die filling productivity, a further investigation of the causes of this segregation was imperative. The present study comprises an investigation of segregation in the multi-die of a single-punch tableting machine, using the discrete element method to determine the causes of size segregation behavior during the entire die filling process. Simulation parameters were determined based on the measurement of physical properties and actual particle size distribution. Multi-sized spherical particle simulations were performed to visualize and characterize size segregation in the feeder and dies. The effects of the friction coefficient and the initial charged mass of the particles—which are important physical operating parameters—on the segregation behavior were investigated. To qualitatively and quantitatively characterize size segregation, the segregation index and the average size of the particles in the feeder and dies were evaluated. The present research demonstrated the feasibility of the method for characterizing the segregation phenomenon during the filling process and revealed that the segregation mechanisms during the filling process. Furthermore, it was shown that a lower particle-wall friction coefficient and a higher charging mass in the feeder would suppress the segregation, which can cast light on the controlling of the segregation in the tableting process.