Experimental and numerical investigation of injection molding with microrib patterns

In this study, experimental and numerical studies were carried out to investigate the transcriptability of microrib structures and flow characteristics in injection molding of such geometry. For this purpose, mold inserts with nine parallel microribs on top of a thick ground plate were designed and fabricated in such a way that the gate location could be varied to change flow directions: parallel or transverse to the microrib structures. By utilizing the fabricated mold insert, the transcriptability affected by gate location and flow direction was experimentally investigated. As for the numerical methods for injection molding filling simulation, we have developed an Interpolated Domain Decomposition Method (IDDM) enabling a coarse mesh for a ground plate and a finer mesh for microstructures. The effect of processing conditions on transcriptability has been extensively investigated. Under various processing conditions, an interesting flow phenomenon similar to “race-tracking” was observed due to “flow-hesitation” in the microribs. The same phenomenon was observed in flow analyses via IDDM, as well as a full 3D analysis. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers