Abstract
This study investigates the effect of particle cohesion on die filling behaviour in a rotary tablet press using a combined Discrete Element Method (DEM) and experimental approach. Microcrystalline Cellulose (MCC) spheres were characterised experimentally and used as the model powder. A validation study is conducted where tablet weight and its variability, obtained from DEM simulations, and corresponding experiments are compared. In addition, Residence Time Distribution (RTD), with both pulse and step change inputs, are obtained numerically and experimentally to further validate the DEM models. A satisfactory agreement between the DEM and experimental results was obtained. Systematic DEM simulations are then performed to explore the influence of powder cohesion on die filling behaviour. The results revealed that increasing powder cohesion reduces tablet weight (uniformity) considerably under constant fill depth. Additionally, more cohesive powders have a propensity to remain in the feed frame for a longer time under similar process conditions. It is also shown that optimal tablet weight with minimal variability could be obtained at intermediate turret speeds, whereas high turret speeds (90 rpm) are associated with lower tablet weight uniformity. Additionally, at low turret speeds, increasing paddle speed to an intermediate level improve process efficiency, notably through increases in mean tablet weight and tablet weight uniformity when fill depth is kept constant. These simulations elucidate the critical factors affecting tablet manufacturing, allowing for the optimisation of process parameters to maximise weight uniformity and performance while minimising experimental burden.