Modeling the Formation of Debossed Features on a Pharmaceutical Tablet

Abstract

The objective of this work was to develop, validate, and implement a modeling methodology for predicting the shape and relative density fields in the vicinity of debossed features on a tablet surface. The resulting model was used to investigate the influence of debossed feature stroke angle and degree of pre-pick, which is expressed as a percentage of the stroke depth, as well as the influence of formulation lubricant on the aforementioned debossed feature parameters. An experimental procedure for measuring formulation (modified) Drucker–Prager Cap parameters is described. These parameters are used in a finite element method simulation that models the formation of a debossed surface feature on a tablet. Techniques for validating the simulation and post-processing the results are also described. The stroke angle and degree of pre-pick significantly influence the debossed feature dimensions, with larger degrees of pre-pick and stroke angles giving debossed features that more closely match the target (embossment) values. Lubrication plays a much weaker role, but did improve the fidelity of the debossed feature slightly. The differences between the debossed and target feature dimensions are due to elastic spring back of the material. The tablet relative density is smallest at the shoulders of the debossed feature and largest at the base of the valley. Although the relative density fields show no obvious trends with stroke angle, the fields are clearly more uniform as the degree of pre-pick increases. The addition of lubricant to the formulation also improves the relative density field uniformity for larger degrees of pre-pick. To improve feature fidelity and decrease the likelihood of damage, larger pre-picks, larger stroke angles, and the addition of a formulation lubricant should be used.