Evaluation of Vacuum Venting for Micro-injection Molding

While the effect of vacuum venting has been reported for injection molding of micro and nanoscale features, the limited research has produced conflicting results. To clarify the positive effect of vacuum venting on replication of microscale features, this work focused on the interactions between vacuum venting and (I) feature size, (2) material type in terms of melt viscosity and wettability, and (3) injection velocity and mold temperature. A metal-polymer hybrid tooling with a range of positive microscale features was employed to mold polystyrene and polymethylmethacrylate parts. Overall, vacuum venting always effective in feature definition (sharpness of edges) enhancement, but provided increases in depth ratio that depended on material (melt viscosity and wettability) and processing conditions (i.e., injection velocity, and mold temperature).