Prediction Model for Flake Line Defects in Metallic Injection Molding: Considering Skin-Core Velocity and Alignment

Metallic injection molding combines aluminum flake metallic pigments with polymers to directly produce components with metallic luster, improving production efficiency and reducing environmental impact. However, flake line defects that occur in regions where ribs or flow paths intersect remain a significant challenge. This study proposes a velocity model that considers the flow characteristics between the surface and core layers and an alignment model that incorporates the orientation of aluminum flakes to predict appearance defects. Through this approach, the mechanisms of appearance defect formation were systematized, and the appearance defects caused by flow velocity differences between the surface and core layers, flake alignment uniformity, and reflection angles were visualized. Both prediction models demonstrated a 50% prediction accuracy, successfully identifying two out of four observed defects. This research addresses the limitations of previous prediction methods, which only considered the surface layer, by introducing a novel approach that accounts for the core layer. It is expected to contribute to reducing defects and improving quality in industries requiring high-quality metallic appearances.