deforming and reforming plastics Flashcards
What is line bending?
Also known as strip heater.
A method of shaping plastic such as acrylic by folding it.
Method of line bending?
Plastic warmed on the heater to become pliable.
Placed in a mould to bend or hold to required shape.
When it cools, it can be taken out and it will be set to the angle.
What is vacuum forming?
Thin plastic is vacuum formed over mould to create “dish like” packaging.
Eg. is plastic biscuit packaging.
What are the PRO and CON of line bending?
PRO - It is useful in batch/one off production as it can create the exact curve needed by hand.
If it goes wrong, it can be done again by re-melting the plastic.
CON - It is inefficient in mass production as it takes a long time to do by hand.
Method of Vacuum Forming?
Plastic sheet placed above mould in vacuum former and clamped.
Electric heater turned on to warm the plastic sheet. Plastic then becomes flexible.
Mould moved upwards and air underneath plastic is vacuumed out to become tight around mould.
Mould is removed to create thin plastic shape.
What is blow moulding?
Ideal for high density polyethylene.
Blows the plastic into the mould to fill out mould.
Often used for mass produced plastic bottles/packaging.
Method of Blow Moulding?
Plastic granules/powder placed into hopper.
Drops it down onto rotating thread and travels along screw whilst being heated.
When reaching mould, compressed air blown into mould to push plastic around the edges of the mould to form hollow shape.
What is extrusion of plastics?
Similar to injection moulding, plastic is fed into longer stock forms such as tubes or planks.
Method of plastic extrusion?
Motor turns granules of plastic though a heater.
Granules melted into liquid and forced through a die to form the shape.
Extrusion then cooled and formed into solid shape. The shape extruded depends on shape of die.
What is 3D printing of plastic?
3D computer aided design (CAD) manufactured on a machine to produce a solid model.
Uses of 3D printing?
It is used in the production of tools, jewellery, textiles and many components of products.
In medical treatment, it can be used to make prosthetic limbs and hearing aids.
