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Plastic Injection Molding Basics

Core fundamentals of the injection molding process

What is Injection Molding?

Injection molding is a manufacturing process where molten plastic is injected into a mold cavity, cooled, and ejected as a solid part. It is the most common method for producing plastic parts in high volumes.

The Molding Cycle

StageDurationDescription
Clamp1-5 secMold closes and clamps shut
Injection0.5-5 secMelt injected into cavity
Packing1-10 secAdditional material packed to compensate shrinkage
Cooling5-60 secPart cools below ejection temperature
Ejection0.5-2 secPart ejected from mold

Key Process Parameters