Abstract:

In the bi⁃color injection molding process， the first shot of the base plastic part remains on the movable mold side and moves with the movable mold to the stationary mold side of the second shot for a mold closing to complete the second shot of encapsulation molding. To address the issue of encapsulation molding on the back of the base plastic part with a side on the movable mold， it is necessary to replace the corresponding insert of the movable mold. To this end， through controlling the sequence of opening and closing actions of the mold， the movable mold slider and insert were moved together by a bent pin fixed on the stationary mold side of the first shot to obtain a replacement action between different inserts of the first and second shots. Then， the extension and retraction of the insert were controlled by limit blocks and return springs. To prevent the base plastic part from adhering to the stationary mold cavity during mold opening， a nitrogen spring⁃driven ejection mechanism for the base plastic part was designed on the stationary mold side of the first shot. To ensure the safe， accurate， and reliable operation of the automatic replacement of inserts， ejection， and other mechanisms， the corresponding safety mechanisms were designed.

Key words: automatic replacement insert, safety mechanism, fixed mold ejector, bi?color injection mold