Basic study of die wall friction in ejection by lateral pressure measurement with the dual partitioning die in compaction

In powder compaction, the ejection characteristics of green compact held in the die affect friction between the green compact side and die wall. The ejection characteristics are important factors for final formability of green compact. Therefore, this research studied factors that affect ejection friction. For ejection friction factors, we sought to measure lateral pressure that acts on the die wall, from compacting until ejection. We found that an increase in ejection friction coefficient does not necessarily increase ejection pressure. This phenomena was caused by lubricant that the compact supplies to the wall. By defining concrete material coefficient for powder, ejection characteristics have been explained. We found that powders with simpler shapes and/or lower yield strengths have superior ejection characteristics.