Compaction analysis and optimisation of convex-faced pharmaceutical tablets using numerical techniques

Capping failure, edge chipping, and non-uniform mechanical properties of convex-faced pharmaceutical tablets are common problems in the pharma industry. In this paper, the finite element method (FEM) and design of experiment techniques are used to determine the optimal shape of convex-faced (CF) pharmaceutical tablet which has more uniform mechanical properties and less capping and chipping tendency. The effects of different geometrical parameters and friction on the compaction responses of convex-faced pharmaceutical tablets were first identified and analysed. An FEM model of the tabletting process was generated using the implicit code ABAQUS and validated against experimental measurements. Response surface methodology was used to establish the relationship between the design variables, represented by the geometrical parameters and friction coefficient, and compaction responses of interest including residual die pressure, relative density variation within a tablet, and relative shear stress at the edge of a tablet. A statistical-based optimisation approach was then used to optimise the shape of CF tablets. The obtained results demonstrated how the geometrical parameters and friction coefficient of CF pharmaceutical tablets strongly affect their compaction behaviour and quality.