Investigating the effect of punch geometry on high speed tableting through radial die-wall pressure monitoring

Abstract

Dwell time mainly depends on punch geometry, so some tableting problems such as capping and lamination could occur at high speed compaction. Robust tools are required to monitor the interaction of punch tip and powder bed at these high speeds. Our aim was to investigate the effect of punch geometry (flat and standard concave) on powder compaction at high speed using radial die-wall pressure (RDWP) as a monitoring tool. Instrumented die guided by compaction simulation was applied for five materials with different compaction behaviors. Flat-faced punch showed higher residual, maximum die-wall pressures, and axial stress transmission than concave punches, p < 0.003. Moreover, flat-faced punches showed less friction upon ejection, p < 0.003. Flat compacts showed higher elastic recovery, tensile strength, and required less work of compaction than convex compacts, p < 0.05. RDWP monitoring was a useful tool to prove that flat-faced punch induced higher radial stresses and particle/particle interactions in comparison to concave punch.