Injection Mold for Cosmetic Bottle Caps

For mold design, the solution adopts a highly efficient 1×12 cavity layout. The hot runner system injects molten plastic directly from the center of the cap's top, effectively reducing gate marks and preserving the integrity of the product's appearance. Both the core and cavity inserts are made of high-quality S136 mold steel, heat-treated to a hardness of HRC 48-50, guaranteeing high precision and wear resistance during long-term mass production. The mold base is manufactured from S50C steel, providing a solid and stable foundation for the entire mold.

The parting line is positioned at the bottom edge of the cap, working in conjunction with a stripper plate ejection structure and an air ejection assist system to achieve smooth and efficient product demolding. For the undercut structure inside the cap, a forced demolding process specific to HDPE material is utilized, simplifying the mold structure and reducing production costs. To optimize molding quality, the design recommends increasing the wall thickness from 0.75mm to 0.85-0.9mm. This adjustment significantly improves melt flowability, minimizing risks such as insufficient filling and stress cracking.

During the mold manufacturing phase, all core components undergo CNC precision machining and EDM (Electrical Discharge Machining), ensuring dimensional tolerances are controlled within ±0.02mm. The 600# polishing on the core and cavity surfaces not only ensures the product's surface finish but also facilitates demolding and extends the mold's service life. In the mold trial stage, key parameters including injection pressure, holding time, and cooling rate are strictly monitored to ensure the final product has a stable weight of 10g, with all performance indicators meeting the design specifications.