Design of a kind of injection mold without core-pulling for beverage plastic closures with tamper-evident band

LUO Da
（Hangzhou Wahaha Group Co. Ltd.， Hangzhou 311215， China）

Abstract：  In order to solve the problems of complex and large，easy to wear on the pulling mechanism parts and short life time of the traditional core pulling structure mold，the forced stripping and three-steps demolding method was investigated on the injection mold to effectively simplify the mold structure and improve the performance. After the analysis of possibility for the replacement of connecting bridges core-pulling mechanism by other simple mechanism or single part，the relationship between the pushing tube and the forming of the connecting bridges was established and the method of transform the pushing tube of the core-pulling mechanism into the forming part of the connecting bridges was brought out. The evaluation of the mold structure，lifetime，manufacturing costs and production efficiency was established. The pilot mold of the new pushing tube instead of the core-pulling mechanism was made and tested on the original injection machine by adjusting the injection parameters. The results indicate that the mold with the news structure is stable，reliable and it can meet the requirements of quality control. Not only mold structure is simple，long life， but also the productivity increases more than doubled.
Key words： plastic closures with tamper-evident bands；injection molding；strip structure without core-pulling