Blow moulding: Bottles, watering cans, containers.
Step 1: A tube of heated and softened polymer is extruded vertically downwards. Tube is called a parison.
Step 2: The mould halves close, trapping the upper end of the parison, effectively sealing it.
Step 3: Hot air is then blown into the parison forcing it out to follow the shape of the mould.
Step 4: The mould effectively cools the polymer, allowing it to be released from the mould.
Step 5: The mould halves are opened and the product is extracted.
Advantages: Once set up, it is a rapid process.
Can produce non-circular shapes.
Disadvantages: Moulds can be expensive.
Can be hard to extract the product from the mould.
Calendaring: Storage containers,
Step 1: The rollers are heated to just above softening point of the thermoplastic.
Step 2: During the rolling process, the plastic ‘dough’ is forces through the gap roller. These rollers determine the thickness of the material.
Step 3: The final roller is the chill roller that cools the material.
Extrusion: stationery holders,
Step 1: Thermoplastic powder is placed in the hopper; this plastic then falls onto the rotating screw, which in turn pushes the material towards a heated section of the extruder.
Step 2: The heaters soften the plastic, which is then forced through the die on to the rotating screw.
Step 3: On exiting the die, the plastic is then cooled using, a water…