Core stabilization by sequential injections

A method for controlling the dimensions of a hollow plastics product injection molded within the cooling cavity of a mold having a core section and a cavity section defining the cooling cavity therebetween and separated by a parting line comprising stabilizing the core section in the cooling cavity and being characterized by the steps of:

• (a) injecting a first plastics material into the cooling cavity so that only a part of the cooling cavity is filled and so that the injected first plastics material does not completely cover the parting line;
• (b) cooling the injected first plastics material in the cooling cavity;
• (c) injecting subsequent to injecting the first plastics material a second plastics material into the cooling cavity so that the cooled injected first plastics material in said part of the cooling cavity stabilizes the core section by impeding movement of the core section caused by injecting the second plastics material and whereby the injected second plastics material fills the cooling cavity to thereby completely cover the parting line and fuses with the cooled previously injected plastics material;
• (d) cooling the injected plastics material in the cooling cavity to thereby solidify the fused unit;
• and
• (e) ejecting the solidified molded unit.