Compaction simulators are increasingly becoming more and more widely used in the development of pharmaceutical tablets. These machines, as the name implies, replicate the movement of the lower and upper punches of a given rotary tablet press through the use of either servo hydraulic or linear screw actuators. This then makes it possible to study the effects of relevant at-scale dynamics, such as compression rate on the tablet properties (e.g., compressibility, compactibility, tabletability) on the bench scale, allowing at-scale development and the significant material consumption it requires to be minimized.
Time-resolved punch displacements used to approximate the punch dynamics of an at-scale press are most often calculated using the model presented in Rippie and Danielson (1981). These calculations are often performed automatically by the software that comes with the compaction simulators, provided known dimensions of the rotary press key components and the punch head profile as well as some assumptions regarding the precompression and ejection mechanisms. This study aims to assess the accuracy of these calculations by comparing the compression profiles provided by the software that accompanies a Huxley-Bertram compaction simulator to those predicted by a finite element method (FEM) simulation. The FEM model simulates the punch movement on a rotary tablet press using the actual geometry of a pilot-scale rotary tablet press and a TSM-B punch. Simulations are performed using different turret speeds, varying levels of pre-compression, different ejection dynamics, and with and without account of machine deformation. For cases where the FEM-predicted time-resolved punch displacements are significantly different from those provided by the compaction simulator software, the FEM predicted results are used to create a custom compression profile for the Huxley-Bertram compaction simulator. MCC and lactose tablets are then compacted using the FEM-predicted compression profile and the one generated by the compaction simulator software. Differences in tablet properties arising from the differing profiles used for making the tablets are discussed.
