Optimizing particle size segregation in vacuum drum-based capsule filling machines: A stirrer design approach

This study investigates particle size segregation within the powder chamber of a vacuum drum-based capsule filling machine using various stirrer types and proposing novel designs to mitigate segregation. The stirrer is essential to the process, ensuring uniform density during volume-based filling. Three lactose grades, comprising 10% fine, 80% medium, and 10% coarse particles, were used, with tracer particles replacing fine or coarse particles, respectively. Dosages were collected over time for a line-array of five bores, and tracer concentrations were analysed using UV-Vis spectrophotometry. By visual assessments and stagnant zone observations particle segregation was evaluated and quantified by normalised tracer concentrations. Both standard and modified stirrers were examined under the same conditions. Stirrer type significantly influenced particle segregation, with the "spike" standard stirrer yielding the highest segregation, while the modified "3-wire^m" and "coreless 3-wire^m" stirrers exhibited superior performance, minimizing differences between fine and coarse particle concentrations and eliminating stagnant zones. These findings highlight promising prospects for further analysing the "3-wire^m" and "coreless 3-wire^m" stirrers. In that respect additional variables such as stirrer speed, rotation direction, and level of vacuum, need to be considered. Stirrer design significantly impacts vacuum drum-based capsule filling machine performance, ensuring reliable pharmaceutical capsule filling. This study offers insights into optimizing the industrial process.