A micro powder injection molding apparatus for high aspect ratio metal micro-structure production

A new variotherm molding apparatus is presented in this paper for the fabrication of high aspect ratio 316L stainless steel micro-structures using micro powder injection molding (mu PIM) technology. The molding apparatus prototype includes an injection mold in which a silicon insert with an array of 24 x 24 ( 576) microcavities is mounted, a set of rapid tempering systems for the mold and a set of vacuum systems. The key advantage of this molding apparatus lies in the real-time monitoring and rapid adjustment of the mold cavity temperature during injection molding and part ejection, which makes molding and demolding of high aspect ratio green micro-structures possible. For example, incomplete filling occurs while injection molding micro-structures of 60 mu m x height 191 mu m with an aspect ratio of 3.2 using a conventional mold. In comparison, smaller micro-structures with higher aspect ratio are produced successfully in the case of the new molding apparatus, e. g. micro-structures of 40 mu m x height 174 mu m with an aspect ratio of 4.35 and 20 mu m x height 160 mu m with an aspect ratio of 8 were molded successfully.