Finite Element Modeling of Powder Compaction: Mini-Tablets in Comparison with Conventionally Sized Tablets

Mini-tablets are considered a promising solid dosage form in the pharmaceutical industry due to advantages such as dosing accuracy, efficiency as a drug delivery system, and alleged improvement in mechanical properties. Nevertheless, only a few experimental studies are available in the literature regarding this topic and technical aspects, such as punch's shape and size effect on the stress and density distribution in the compact mini-tablets, are still not fully investigated.

In this paper, the influence of powder properties and process parameters, such as punch shape and size, on the evolution of mechanical properties during the tableting process and the potential occurrence of tablet defects are investigated using the mechanistic modeling approach, Finite Element Method (FEM).

The numerical simulation cases consist of four different die sizes, mini-tablets of 2 mm, and 3 mm, and conventionally sized tablets of 8 mm and 11.28 mm. Each tablet size is simulated using four distinctive excipients, Avicel^® PH-102, Kollidon^® VA64, Pearlitol^® 100SD, and Supertab^® 11SD, and two different punch geometries, a flat-face punch, and a bevel edge punch.

The model predictions in terms of stress and density distribution at different stages of the compaction process indicate similar behavior in terms of density and stress distribution profiles between the conventionally sized tablets and mini-tablets for a particular excipient.

Based on tablet size, small localized differences are noted (e.g., low-density regions, high shear bands, and heterogeneous density profiles), suggesting a possible risk of tableting defects for conventionally sized tablets compared to mini-tablets. Furthermore, it is observed that bevel-edged tablets could facilitate the formation of cracks, leading to possible capping failure.