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Injection molding

Plastic forming process where the plastic pellets are fed in and melted in a container with a rotating screw and pressed into a mold.

Illustration of Injection molding

The process

Plastic pellets [1] are supplied via a hopper into a rotating screw [2] whose spiral shape moves the pellet forward through a heated chamber [3].The pellets are heated gradually and turns into a homogeneous plastic melt as it approaches the end of the helical screw.

The molten mass is pressed into a mold [4] as the entire screw is pushed forward by an applied pressing force. After the mass solidified the mold halves are separated and the part is removed using ejector pins [5].

Advantages and disadvantages
In comparison with alternative methods
Flexible selection of materials
Low cost of labor
Complex shapes
Low wastage
Little or almost no need for subsequent processing
High investment costs for utilities
Difficult to calculate the exact cost of the process