The sequential process during the injection of the melt into the cavity until the part is cooled down, is called mold filling phase.
After the volumetric filling of the cavity (95% to 98% of the cavities volume), (A) there is a switch-over from injection to packing.
During this phase the material is packed and pressed to the mold wall (B).
After the switch over point the complete filling (100%) of the cavity takes place.
During the packing phase (C) the material will be compressed is in good contact with the mold wall.
The plastic shrinks while it is cooling down (approximately 0,2 – 2,0 %).
Shrinkage is compensated in the packing phase due to a material delivery through the melting core. This is important to ensure the dimensions of the part itself.
After the packing phase, cooling phase will start (D). Here the part will be cooled down to a point, where the dimensional stability can be ensured (to ejection temperature) and ejection can be done without deformations on the part.

Mold Filling Phase in Plastic Industry

Injection molding process: Course of the pressure curve (ideal).

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This glossary of plastic industry is provided by PLEXPERT Canada Inc.