Pressure Distribution in Shallow Rectangular and Circular Dies Using Different Filling Methods

Abstract

The process of die filling is a significant unit operation in many industries. The inhomogeneity of fill has been known to cause tablet and compact quality issues, such as lamination, capping, and distortion. Therefore, the goal of this research was to investigate and compare the uniformity of pressure distribution of four die filling methods, i.e., feed shoe, rotational rainy, point feed, and pneumatic. To study the powder deposition characteristics, rectangular (32 × 30 mm and 6.5 mm deep) and circular (35 mm in diameter and 6.5 mm deep) cross-sectional shallow dies of equal volume were used. Due to their industrial importance, test materials used were a battery powder mixture (BPM) and microcrystalline cellulose (Avicel PH102). A second-generation pressure deposition tester with circular and square feed shoe tube cross sections was used to measure the two powders’ pressure distribution characteristics. To evaluate the symmetry of measured pressure distribution profiles, variance metrics and uniformity analysis were used. Analysis of results showed that: (1) contour plot analysis was the most reliable method for evaluating deposition characteristics; (2) for all filling methods, the circular die generated higher uniformity than the rectangular die; (3) PDT-II is capable of filling the die at very high speed and was determined to be the fastest filling method in this study; (4) the average uniformity pressure distribution for feed shoe, rainy, and point feed are 55%, 77%, and 64%, respectively; and (5) the rotational rainy fill method appears to be the most appropriate filling method to generate the highest uniformity pressure distribution inside the die.