[learn_more caption=”Mazel”] Mazel¹

H. Diarra¹

V. Busignies¹

P. Tchoreloff¹

¹ Univ. Bordeaux, CNRS, Bordeaux INP, ENSAM, I2M, UMR 5295, F-33000 Bordeaux, France[/learn_more]

Abstract

Capping is a classical manufacturing problem for tablets, which is known to affect more biconvex tablets than flat-faced ones. One reason could be the development of a higher residual die-wall pressure during unloading. Unfortunately, contradictory results were published on the subject. In this work, the evolution of the die-wall pressure during the compaction of biconvex tablets was studied experimentally and using FEM modelling. It was compared with the case of flat-faced tablets.

Experimental and numerical results showed that, during the compression of biconvex tablet, a lower maximum die-wall pressure and a higher residual die-wall pressure were obtained compared to the case of flat-faced tablet. Moreover, both approaches showed, for biconvex tablets, a temporary increase of the die-wall pressure at the end of the unloading phase. FEM demonstrated that this phenomenon was due to a gradual loss of contact between the punch and the tablet from the side to the center. This complex unloading behavior causes the temporary increase of the die-wall pressure and the development of a shear stress between the convex part and the land of the tablet. This could explain the capping tendency of biconvex tablets.