An apparatus for the investigation of die wall friction during compaction

Abstract

A “moving-die” apparatus is described for use in the investigation of die wall friction during the compaction of powders. The powder can be compressed at constant rates varying from 344–860 kg/sec; the die can be moved at a constant rate at values of 0.1–0.25 cm/sec. The apparatus can also be used to apply the force necessary to cause shear in a punch penetration test for the measurement of shear strength of the ejected compacts. Preliminary experiments with 20–30 mesh crystalline sucrose indicate that values of die reaction, Fd, and ejection force, Fe, increase with increased applied pressure. For a given compaction pressure, Fe and Fd decreased as the rate of application of the compacting force increased. For the range of rates available Fd was independent of the rate of movement of the die. The shear strength of ejected compacts prepared at a constant pressure increased with increase in the rate at which the shear force was applied.