Measuring of capping phenomena in powder compaction process using X-ray computed tomography

Suzuki, Michitaka*; Tanaka, Yutaka*; Iimura, Kenji*; Satone, Hiroshi*; Ishii, Katsunori

no journal, , 

The capping phenomenon is one of the important causes of the powder molding trouble. The research of the capping such as how to occur and what kind of condition related to the phenomena is not cleared still now. The packing particles for our tests were 20-150um spherical Alumina granules and the sieved narrow sized granules were also used. The compression tests were performed by a material-tester. The capping region could be detected from X-ray computed tomographic images and the depth of capping area was measured. It's clear that the capping phenomena are easy to occur at small compression displacement in the case of wider size distributed granules 20-150um. It comes from the higher adhesion force between fine powder and the piston or the mold surface. The depth of capping is decreasing with the increase in displacement. In the conclusion, the capping phenomena can be prevented to use coarser mono-sized granules for compression molding.