Abstract
Consistently complete die filling during pharmaceutical tablet manufacturing processes is
necessary to ensure consistent dosages of the tablets produced. This project investigates the
impact of several factors on the filling completeness (quantified by the fill ratio) achieved
during different die filling situations. The study employed an experimental design using several
model die filling systems, some of which incorporated key components from industrial die
filling systems. The findings show that, for free flowing and cohesive powders, the fill ratio is
approximately 1 when the filling to suction velocity ratio does not exceed the critical velocity
ratio. Once the critical velocity ratio is exceeded, the fill ratio decreases according to an
equation developed through this work. The individual values of the filling and suction
velocities, and the filling to suction velocity ratio, are significant in determining the fill ratio.
Adding lubricant increases the fill ratio when cohesive powders are used but has no effect when
using free flowing powders. In the context of forced fed linear die filling, high stirrer velocities
increase the fill ratio when cohesive powders are used. Stirrer velocity has no effect on the fill
ratio when free flowing powders are used. Utilizing suction filling with a commercially
available HB100 feeding shoe results in lower fill ratios for both cohesive and free flowing
powders, relative to gravity filling. Replacing the original wire stirrer of the HB100 feeding
shoe with a novel ribbon stirrer increases the fill ratio when cohesive powders are used but has
no effect when free flowing powders are used. Cohesive powders behave differently in forced
fed linear die filling systems than in forced fed rotary die filling systems; free flowing powders
behave identically across both system types. The findings allow for improved tailoring of die
filling processes to specific powder blends required for pharmaceutical tablet manufacturing.