on 08/03/2017



Special Prize

Beijing University of Chemical Technology

Improvement on the 2.5 Inch NPSM Screw Thread Requirement of a Plastic Bottle Cap


The goal of this project was to minimize the volumetric shrinkage of a plastic bottle cap in order to meet the 2.5 inch NPSM screw thread requirement without compromising the final product quality. With this goal in mind, an in-depth study on the mold cavity dimensional design was conducted in hopes of successfully controlling the precision of the screw thread within the acceptable tolerance.


Two important processing parameters that influence the part shrinkage are packing pressure and packing time. In this study, Moldex3D was utilized to optimize the part/mold design and further identify the appropriate packing conditions to successfully adhere to the NPSM screw thread requirement.


  • BUCT was able to successfully control the precision of the screw within the acceptable tolerance. The part reject rate was significantly lowered from 90% to 5% which ultimately helped generate a greater business value for manufacturing companies, as well as, reducing material wastage.

Software used

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