Polymers Flashcards
Manufacturing Processes
What items are manufactured using injection moulding?
Complex items/parts:
-Casing on electrical products (vaccum cleaners)
-Bottle caps
-Screw threads
-internal clip fastenings
-battery housing
-circuit board holders
What production method is used for injection moulding and why?
Large scale mass production.
OR
Continuous production.
This is due to high setup costs of equipment and moulds.
Explain the injection moulding process
- Thermoplastic granules are poured into the hopper.
- A screw thread is rotated by a motor which pulls the granules through the chamber, past the electric heaters.
- The polymer is melted by the heaters.
- When a sufficient charge of molten polymer has formed at the end of the screw, a hydraulic ram forces the screw thread forward, injecting polymer into the mould.
- The mould is water cooled, and ejector pins push the moulding out.
- Excess polymer is trimmed off. Formers/jigs are used to maintain dimensional accuracy while it cools fully.
What does the injection moulding diagram look like?
Look at google.
What does blow moulding produce? What polymers does it use?
Bottles and hollow products.
Uses PET, LDPE, HDPE and PP.
What sort of production is used for blow moulding and why?
Continuous production due to high setup costs associated with equipment/moulds.
Explain the extrusion blow moulding process
- Polymer is fed into the hopper
- An Archimedean screw pulls the polymer through the heated section, which melts it.
- The melted polymer is extruded as a hollow tube which is called a parison.
- Mould sides close around the parison and air is injected into the mould, forcing the polymer to the sides.
- Polymer is allowed to cool for a few seconds, then the mould opens, and the finished bottle is ejected.
What does the blow moulding diagram look like?
Look at google.
What is injection blow moulding?
Combines injection moulding and blow moulding by using injection moulded preforms.
These are mini bottles that have been injection moulded, then go through the blow moulding process.
This is usually done when bottles have threaded heads/closed bottoms-
where more tolerance is
needed.
What does the Extrusion method produce?
Solid rods
Hollow tubes
I and T sections or channels
Coat wiring with polymer (PVC) for insulation.
What sort of production is used for extrusion?
Continuous production of stock material.
Only used by specialist manufacturers.
Explain the Extrusion manufacturing process
- Polymer granules are loaded into the hopper
- An Archimedean screw moves the polymer granules past the heaters, which soften the polymer.
- When sufficient polymer has melted, the hydraulic ram pushed the Archimedean screw which forces the polymer through a steel die. The shape of the die determines the shape of the extrusion.
- Extrusion is supported by rollers as it leaves the die and is water cooled.
- Extrusion is then cut to the desired length.
What does the extrusion diagram look like?
Google it.
