Study on the Orientation of Two-dimensional Shaped Additives in Injection Molded Specimen Containing Protrusion Shape

A flat metal additive is added into the resin to create a metallic feel on the surface of an injection molded prod-uct. When injection is made using a resin mixed with two-dimensional flat additives, the additives are oriented parallel to the surface due to the fountain flow in the cavity, giving a metallic texture. However, if the product has protrusions such as ribs or hooks, the flow is not uniform and the orientation of the additive changes, resulting in surface defects. This study predicted the orientation of two-dimensional shaped additives in injection molding specimens with protrusions through simulation and compared them with experiments. The orientation of the two-dimensional additive and surface defects were observed by varying the thickness and direction of the ribs and hooks in the specimen. Surface defects depending on the orientation of the additive were observed on both the protruding side and the opposite side of the protruding surface. In the simulation, surface defects on the protruding side were predicted, but surface defects on the opposite side of the protrusion were not predicted. Through this study, the orientation mechanism of the two-dimensional shaped additive in the specimen containing a protruded shape was presented.