Blow moulding involves blowing air into a plastic tube called a parison to make it take the shape of a mold, and is used to make bottles and hollow toys. PVC and polythene are common materials. Injection moulding melts plastic granules using a heated barrel and screw, then injects the molten plastic into a mold cavity under pressure. It is often used to make toys from high impact polystyrene. Compression moulding uses a hydraulically operated press with two heated mold platens to precisely mold materials between the platens under pressure and heat.

5. Blow Moulding
• Used to make
bottles and hollow
toys.
• Air is blown into a
plastic tube, called
a parison, to take
the shape of the
mould.
• PVC and polythene
are often used.

7. Injection Moulding
Powder or granules from a
hopper into a steel barrel with a
rotating screw. The barrel is
surrounded by heaters The screw
is forced back as plastic collects
at the end of the barrel .
Once a sufficient charge
of melted plastic has
accumulated a hydraulic ram
forces the screw forward
injecting the thermoplastic
through a sprue into the mould
cavity.

8. Injection Moulding
Pressure is kept on the mould
until the plastic has cooled
sufficiently
for the mould to be opened and
the component ejected.
Materials used
Normally thermoplastics are used in this
process although a few thermosetting plastics can also be
injection moulded.
Toy made from high impact polystyrene (HIPS).

15. COMPRESSION MOULDING
 1. Uses a hydraulically operated press.
2. Press consists of two heated mold platens, one stationary and one
movable .
3. Platens have either “T” slots or tapped holes to fix the mold halves to
the platens.
4. Tie Rods, usually 4, provide for precise alignment as the press is
opened and closed.
5.The press open and shut height and the platen temperature are
controlled.