Observation of instabilities in flow front during micro injection molding process

This work has investigated filling characteristics during injection molding of a thin‐plate with microchannel patterns on it. To conduct molding experiments, an injection mold and mold inserts with microchannel patterns were designed and built. The experiments were conducted for three different channel sizes, and the results are analyzed. An unstable filling flow was observed in microscopic images for the smallest channel size. The front advanced with continuous creation and merge of microballs, which looked like teeth on the gum. We have analyzed this phenomenon and argued that there exists a critical channel width where such instability takes places. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers