Effect of a pressurized cavity on the replication of micro-patterns with injection molding

In this investigation, we studied the effect of the cavity air pressure on the replication of micro-patterns in injection molding. When pressure is applied to the cavity air, the pressure at the flow front is also increased and thus the overall pressure gradient in the polymer melt is lowered. Therefore, the melt flow in the cavity becomes slower providing more time for the polymer melt to fill the patterns on the cavity surface resulting in the improvement of replication of the microscopic pattern. We carried out experiments for molds with a macroscopic pattern (ribs) and a microscopic pattern on the surface. In order to evaluate the quality of replication, we measured the filling heights of patterns with different ratio of the cavity air pressure to the injection pressure. The results showed that the application of cavity pressure helps the replication of patterns both for macroscopic and microscopic scales.