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Water assisted injection molding

Forming process where a molten polymer mass along with water is injected into a mold to create a hollow component.

Beskrivning
Illustration of Water assisted 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 in a mold [4] as the entire screw is pushed forward by an applied pressing force and after the mold is partially filled, water [5] is injected which pushes the melt and fills the mold while a hollow is created in the part. The water is flushed through the part and discharged through an outlet [6] on the other end of the piece.

There are some different variations on how water assisted injections is done.

After the mass solidified so separated mold halves and the part removed using ejector [7].

Water assisted injection molding
Advantages and disadvantages
In comparison with alternative methods
Direct cooling inside the mold
Smooth surface of the internal channels
Very good distribution of the wall thickness
Useful for thick walls
Useful for large diameters
Suitable for long flow paths
Short cycle
Low cost of supporting materials
Corrosion of steel because of water
Some materials are more difficult to cast
Removal of water after casting required