Abstract
The relation between variation of filling-weight and powder-flowability was studied in connection with filling mechanism. OCF-120 and Hofliger-Karg-GKF-1000 were used as a capsule-filling machine of the pouring type and of the stamping type, respectively. The angle of repose, the minimum orifice diameter and the discharge rate through orifices were measured. The minimum orifice diameter was closely related to the discharge rate through orifices. No good correlations were found between the angle of repose and the minimum orifice diameter. The angle of repose was used as an index of flowability representing the mobility of the particles on the surface of a powder bed and the minimum orifice diameter was used as one representing the mobility of the particles in a powder bed under dynamic conditions. In the case of OCF-120, a good correlation between the variation of filling-weight and the minimum orifice diameter was found. In the case of Hofliger-Karg-GKF-1000, the variation of filling-weight was closely related to the angle of repose but a minimum point appeared in the plots of the angle of repose vs. the coefficient of variation of filling-weight. This finding is explained as follows : as the angle of repose increases, the variation of filling-weight is governed by both the increasing factor and the decreasing factor, namely the variation of the powder-bed-height in the filling box and that of the amounts of jumping-out of the filled powder, respectively.
