Which process involves extruding a tube of molten plastic between two halves of a mould and blowing air to form the product?

• A. Vacuum Forming
• B. Injection Moulding
• C. Extrusion Moulding
• D. Blow Moulding

Answer: (D)

Blow moulding forms hollow plastic items by inflating a tube of molten plastic inside a two-part mould. The process begins by extruding a parison, a short tube of molten plastic, between the mould halves. Once in place, air is blown into the parison, pressing it against the interior walls of the mould and giving the part its final shape as it cools. This method is ideal for bottles and similar hollow shapes. It differs from vacuum forming, which uses a sheet of plastic pulled into a mould by vacuum; from injection moulding, which injects molten plastic into a mould cavity; and from extrusion moulding, which isn’t about inflating a tube inside a mould to form a hollow object.