A DEM approach to assess the influence of the paddle wheel shape on force feeding during pharmaceutical tableting
Pharmaceutical tablet quality is tightly controlled to ensure the patient’s safety. Though the tableting process is a well-known and accepted approach, process understanding is frequently built upon long-time experience of the operators. This is also true for the first step in tableting, the die filling where the powder is fed from the hopper through a force feeding system into the rotating dies of the turret. The current study considers a three-chambered force feeder of a FETTE 1200i, with the focus to evaluate the influence of the paddle wheel shape, which may either be of cylindrical or cuboid shaped blades, on tablet quality. A numerical approach utilizing the discrete element method allowed to compute the powder transfer in the tablet press which helps in identifying the optimal paddle wheel shape configuration. For instance, at a low turret – high paddle wheel speed, the cylindrical configuration revealed highest quality with respect to tablet mass, tablet mass variation, and content uniformity. In contrast, the cuboid configuration indicated better quality at a high turret – low paddle wheel speed. In addition, the detailed analysis of macroscopic and microscopic powder flow phenomena within the force feeder was performed which improves general process understanding in pharmaceutical development.
Keywords: Force feeder, Paddle wheel shape, Tablet quality, Discrete element method, Die filling