Forming and Shaping Techniques – GCSE Design and Technology Eduqas Revision

Forming and Shaping Techniques for Polymers

Injection Moulding

Injection moulding is a common method used to shape polymers, particularly thermoplastics.
The process involves heating polymer granules until they soften into a liquid state, which is then injected under pressure into a mould.
After the material cools and hardens, the mould is opened, and the part is ejected.
This process allows for high volume production of complex shapes that require minimal finishing.
Due to substantial setup costs, injection moulding is mainly used for long production runs.

Blow Moulding

Blow moulding is typically used for the manufacture of hollow objects such as plastic bottles.
The process involves heating a plastic preform, which is then expanded using air pressure into a mould to form the desired shape.
On cooling, the polymer hardens and takes the shape of the mould.
The mould is then opened, and the part is removed.

Extrusion

Extrusion is another common technique used to shape polymers.
This process involves heating and mechanically pushing a polymer through a shaped die to form a continuous profile, like a tube or sheet.
The extrudate is then cut to length once it has cooled.

Compression Moulding

Compression moulding is a high-pressure forming technique ideal for high strength applications, often used with thermosetting polymers.
The process involves placing a pre-heated polymer in an open, heated mould.
The mould is then closed, and heat and pressure are applied until the material fills the mould.
On cooling, the material is hardened and the mould is opened to remove the part.

Rotational Moulding

Rotational moulding allows for the creation of large, hollow sections and is used for products like play equipment and tanks.
The process involves slowly rotating a mould that contains a small amount of polymer.
As the rotation continues, the polymer adheres to and coats the internal surface of the mould.
This process is repeated until the desired thickness is achieved.

Vacuum Forming

Vacum forming is commonly used with thermoforming plastics.
This process requires a mould in which the heated plastic sheet is placed.
A vacuum is applied, pulling the plastic sheet over the mould to form the desired shape.
On cooling, the plastic hardens and retains the mould’s shape.