Impact of roll gap and screen size in the post-compaction dynamics of roller compaction and mill system: A DEM study

¹ Pfizer Research and Development, Pfizer Healthcare India Pvt. Ltd., Chennai, India
² Worldwide Research and Development, Pfizer Products India Pvt Ltd., Mumbai, India

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 1 December 2025

Abstract

In the pharmaceutical industry, managing the flow properties of powder blends is challenging due to their poor flowability. Roller compaction mill, a key granulation technique, enhances the processability of these blends by compressing powders into dense ribbons, which are then milled into granules. This study employs Discrete Element Method (DEM) simulation to analyze the mechanical behavior and post-compaction dynamics of pharmaceutical ribbons, focusing on roll gap and screen size. The simulations reveal that the ribbon expands by up to 20% upon exiting the roller, with significant changes in volume fraction due to variations in roll gap. When the ribbon interacts with the mill impellers, it breaks upon contact, resulting in the formation of smaller clusters of particles as it passes through the screen. This study highlights the critical impact of screen size on particle size distribution (PSD), cluster count, and total volume. Moreover, the effect of roll gap on solid fraction of the ribbon and regional cluster distribution are studied thoroughly. Clearly, adjusting mill-screen design could optimize milling results, emphasizing the importance of controlling mechanical settings for better product uniformity and efficiency in solid dosage form manufacturing.