Polymer Manufacturing Processes Flashcards
Injection Moulding
-Plastic granules (plus any other additive) are placed in the hopper.
-The granule mixture falls through the hopper onto the Archimedean screw.
-The Archimedean screw is rotated, moving the polymer forwards.
-As the polymer moves forward past the heaters it becomes softened due to friction and the heat from the heaters.
-When the shot chamber becomes full of molten polymer the rotation of the screw stops.
-The hydraulic ram forces the molten polymer through the feed hole and into the mould.
-Pressure from the ram ensures the mould cavity has been filled.
-When sufficient time has passed to allow the polymer to cool and solidify (a matter of seconds) the mould halves are opened and ejector pins release the product from the mould.
Extrusion Blow Moulding
Granules fed through hoper to Archimedean screw, turned by motor.
Heated to become a liquid
Extruded to a hollow tube (parison) in an aluminium mould.
Mould pinches the end of the Parison to make seal- compressed air put in so will expand to fill the mould.
Polymer cools and the part is ejected.
Rotational Moulding
Mould opened, set amount of thermoplastic polymer is inserted, then mould is clamped shut.
Mould rotates on a spindle arm, whole thing moves to heating station.
Polymer melts and is liquefied, covers all sides.
Cooling station- polymer ‘freezes’
Back to starting point, mould opens and part is ejected.
