The effect of different feed frame components on the powder behavior and the residence time distribution with regard to the continuous manufacturing of tablets

The present study focused on the effect of different feed frame components on the residence time distribution of a three-chamber feed frame system (Fill-O-Matic). A production-scale rotary tablet press was used to simulate the industrial manufacture of tablets. The powder residence time distribution was used to characterize the powder behavior in the Fill-O-Matic. Therefore, two powder blends based on microcrystalline cellulose, one of them serving as a plain powder blend (MCC blend) and the other blend (tracer blend) spray colored with an indigo carmine solution by a fluid bed granulator, were used. With these powder blends, the effect of the reduction of the Fill-O-Matic volume with a perspex disc on the residence time distribution was compared with the standard configuration of the Fill-O-Matic. Furthermore, the filling wheel design with regard to the rod shape and different gap size configurations between the feed frame and the die disc were investigated. Interestingly, the reduction of the feed frame volume led to a remarkable decrease of the mean residence time and the mean centered variance. Moreover, the results of the filling wheel design showed that the rod shape of the filling wheels had a high influence on the intermixing of the powder particles in the filling chamber, whereas the corresponding tablet weights and their relative standard deviation were not affected. The gap size between the feed frame and the die disc had low influence on the residence time distribution but an effect on the tablet weights and their standard deviation.