Vacuum forming is a technique used to shape plastics by heating a plastic sheet and forming it over a mold using atmospheric pressure and vacuum. The process involves clamping a heated plastic sheet over a mold, turning on a vacuum to pull the sheet tightly over the mold, then removing the formed plastic piece once cooled. Vacuum forming is commonly used to make unusual shapes that would be difficult with other techniques.

2. Manufacturing Processess
of Plastics

3. VACUUM FORMING
Vacuum forming is a technique that is
used to shape a variety of plastics. In
school it is used to form/shape thin
plastic, usually plastics such as;
polythene and perspex. Vacuum
forming is used when an unusual
shape like a ‘dish’ or a box-like shape
is needed.
A TYPICAL VACUUM FORMER

4. THE STAGES INVOLVED IN VACUUM FORMING
1. First, a former is made from a
material such as a soft wood. The
edges or sides are shaped at an
angle so that when the plastic is
formed over it, the former can be
removed easily.

5. 2. The former is placed in a vacuum former

6. 3. A sheet of plastic (for example, compressed polystyrene) is clamped in
position above the mould.

7. 4. The heater is then turned on and the plastic slowly becomes soft and
pliable as it heats up. The plastic can be seen to 'warp' and 'distort' as the
surface expands.

8. 5. After a few minutes the plastic is ready for ‘forming’ as it becomes very
flexible.

9. 6. The heater is turned off and the mould is moved upwards by lifting the
lever until it locks in position.

10. 7. The 'vacuum' is turned on and
this pumps out all the air beneath
the plastic sheet. Atmospheric
pressure above the plastic sheet
pushes it down on the mould. At
this stage the shape of the mould
can be clearly seen through the
plastic sheet. When the plastic has
cooled sufficiently the vacuum
pump is switched off.

11. 8. The plastic sheet is removed from the vacuum former. The sheet has the
shape of the former pressed into its surface.
9. The excess plastic is trimmed so that only the plastic bowl remains - the
completed item. An enlarged view of the final dish is seen opposite.

14. When plastic is used to make a
large number of identical
products, industrial processes are
used. Specialized machines are
used to mass produce products.
To the right is an example of a
vacuum formed toy. The simple
'lorry' mould has been placed in a
vacuum former and a compressed
polystyrene sheet has been
placed above it. The polystyrene
has been heated and then
vacuum formed to the shape of
the mould.

15. The mobile phone seen below has plain packaging. The back is made from
card with a lacquered, gloss finish. The front is manufactured from vacuum
formed high density polystyrene. The polystyrene is transparent which
means that the mobile phone can be seen through it. This type of
packaging is called 'blister packaging'.

16. Materials such as polystyrene, nylon, polypropylene and
polythene can be used in a process called injection
moulding. These are thermoplastics - this means when
they are heated and then pressured in a mould they can
be formed into different shapes.
The DVD Storage unit seen opposite has been made in
one piece using this process
Injection Moulding

17. What similarities and differences can you identify between
the vacuum forming and injection moulding processes?
Injection moulding

19. Injection Moulding (Gas Assisted)
Developments over the past years in Gas Assisted Moulding or (Gas Assisted Molding to use
the US spelling or Gas Injection Moulding being a common reference term) have resulted in
advances in the way in which injection moulded components are manufactured. Enhanced
quality, reduced cycle times and component weight reductions can be achieved by the process.
Typical Materials Used:
Acrylonitrile-Butadiene-Styrene
Typical Products Produced:
Power-tool housing, Telephone

21. Blow Moulding
Blow moulding follows the same stages of
manufacture as injection moulding. HDPE (high
density polyethylene) is ideal for this type of
manufacturing technology .The HDPE granules /
powder is placed into the hopper. It drops down on to
a rotating thread and travels along its distance.
During this process the granules / powder is heated
and becomes fluid.
However, when it reaches the mould compressed air is
also blown into the mould. This pushes the HDPE
around the edges of the mould, forming a hollow
shape, in this case the recycling bin.

22. What similarities and differences can you identify between
the blow moulding and vacuum forming processes?
Blow moulding

23. Blow Moulding is infact Injection Blow
Moulding

26. When the HDPE is cool
it is removed from the
mould and excess HDPE
is trimmed away -
leaving the bin.

27. Injection Stretch Blow Moulding
Injection stretch blow moulding is used for the production of high quality containers.
Typical Materials Used:
Polyethylene - Terephthalate (PET)
Typical Products Produced:
Carbonated and soft drink bottles, Cooking oil containers, Agrochemical containers Health and oral
hygiene products and Bathroom and toiletry products

29. Insert Moulding
Inserts can either be incorporated at the time of the moulding process, or be inserted as a
post moulding operation. When incorporated as part of the moulding process, the inserts
can either be loaded by robot assistance or by the process operator. If the inserts are
applied as a post moulding operation, they can usually be applied any time after the
moulding process. In some cases, they are inserted as part of a series of post moulding
operations. This helping to minimize the actual cost of insertion. The fundamentals of
process speed (and economics), and process repetition must be borne in mind when
making the decision when to apply the insert. It is not good practice to allow the cycle time
to vary from shot to shot; this can have an adverse effect on the quality

31. Rotational Moulding
Rotational moulding (often referred to as Rotamoulding or Rotomoulding) is a
process used for producing hollow plastic products. By using additional post-
moulding operations, complex components can be produced enabling the
process to compete effectively with other moulding and extrusion practices.
Rotational moulding differs from other processing methods in that the heating,
melting, shaping, and cooling stages all occur after the polymer is placed in the
mould, therefore no external pressure is applied during forming.
This provides the following advantages Economically produced large products,
Minimum design constraints, Stress-free products, No polymer weld lines and
Comparatively low mould costs.

34. What is the difference between male and female
moulds?
Compression moulding

35. Moulding through the force of compression is another very common industrial process. The
materials used are melamine formaldehyde, phenol and urea. These materials can be formed
into different shapes through applying both heat and pressure, other plastics do no have
these properties
The stages are as follows:
1. The mould is heated.
2. A 'slug' or piece of the selected plastic is placed into the
mould and warms up.
3. The hydraulic press begins to move down when the
plastic has reached the correct temperature..
4. As the upper and lower mould meet, the plastic is
compressed into the shape of the mould.
5. The upper mould moves upwards and the plastic piece
(in this case a tray) is removed.

36. What products can you think of that have been
manufactured using a strip heater?
Line bending

37. The desk organiser seen opposite has a steel wire frame
and plastic shelves. The selves have been folder on a strip
heater. This heats the plastic along a line so that it
becomes soft and flexible. It can then be folded to almost
any angle. Thermoplastics such as Acrylic (Perspex) are
most suitable for this type of product as they can be
shaped when heated.
The diagram below shows the ‘disassembled’ desk
organiser. The shelves have been removed to reveal the
steel frame behind it. When the shelves clip back on to the
frame, the organiser it forms can ‘free stand’ on a desk.
The desk organiser can be used to hold folders and paper
etc.....

38. Extrusion
Materials such as polystyrene, nylon, polypropylene and polythene can be used in a
process called extrusion. These are thermoplastics - this means when they are heated
and then pressured in a mould they can be formed into different shapes and sections
A machine used to extrude materials is very similar to the injection moulding machine. A
motor turns a thread which feeds granules of plastic through a heater. The granules melt
into a liquid which is forced through a die, forming a long 'tube like' shape. The
extrusion is then cooled and forms a solid shape. The shape of the die determines the
shape of the tube.

39. Can you think of any other products that are
manufactured using extrusion?
Extrusion

40. How an extruder works

41. Below are examples of the type of shapes (sections) that can be extruded using
an extrusion machine.

42. Plastics have excellent surface qualities. As they are
self-finishing, plastics require little or no surface finish.
However, when designers want a specific colour or texture,
spray paints can be used.
Use wet and dry paper (wet) to smooth the surface down
and create a ‘key’ for the primer to grip to.
Primer is used to create an undercoat to protect the plastic
and provide a good surface finish for the top coat. The
primer should be rubbed down using wet and dry paper
between coats.
Top coat is applied once the primer has completely
hardened. There are different surface textures; gloss, matt
and metallic being the most common. Top coat is applied in
several layers to build up a thick, tough surface layer on the
top of the primer.
Finishing techniques

43. Plastics are very useful materials. They are durable, easy to join, self-
finishing, easy to mould and not susceptible to rot or sust. However,
sometimes their properties are enhanced by combining them with other
materials.
Carbon fibre can be added to thermosetting plastics to improve their
strength. Golf clubs, tennis racquets, cycle frames and fishing rods are
made using carbon fibre composite.
Plastics combined with other materials

44. Working with plastics – keywords