Manufacturing in Plastics Thermoplastic Processes

© Ideas In2 Action 2006 Extrusion The plastic is heated and when molten forced under pressure through a die As the plastic leaves the die in its determined shape it is instantly cooled in water troughs and the hardened extrusion is either coiled or cut into sections

© Ideas In2 Action 2006 Extrusion (cont’d) Thermoplastics such as PVC, and nylon are used in the extrusion process

© Ideas In2 Action 2006 EXTRUSION BLOW- MOULDING The cycle 1. A tube of plastic called a parison is extruded into an open two-part mould 2. Mould closes to pinch the mould and air is blown into the tube forcing the plastic against the insides of the mould 3. The mould is opened to release the plastic shape and the cycle begins again.

© Ideas In2 Action 2006 EXTRUSION BLOW- MOULDING (cont’d) Process for making bottles, milk containers, engine oil containers and hollow toys PVC, Polythene and polypropylene are common blow moulding materials

© Ideas In2 Action 2006 Injection moulding Making products by injecting molten plastic into a split mould Polythene, polystyrene, polypropylene and nylon are typical injection moulding materials

© Ideas In2 Action 2006 Injection moulding (cont’d) The cycle 1. Granules are fed into the heating barrel via a hopper whilst the die is also being warmed to 60 degrees. The die is empty at this stage 2. Molten plastic is injected into the mould to fill the cavity via a sprue. The die is water cooled to enable the plastic to harden in the mould 3. The component is the ejected and the cycle is repeated

© Ideas In2 Action 2006 Injection moulding (cont’d) Portable power tool casings Domestic powered utensils Airfix model kits Vacuum cleaners Bottle caps Fixtures and snap fittings

© Ideas In2 Action 2006 Vacuum forming cont’d Polystyrene, ABS, acrylic and PVC are typical vacuum forming materials

© Ideas In2 Action 2006 Vacuum forming Packaging –egg boxes, chocolate liners, point of sale packaging Seed trays Shop signs and fittings Motor car dash boards and bumpers Wash basins, shower trays and baths

© Ideas In2 Action 2006 Rotational casting Litter bins Traffic cones Liquid self-feeding system for cattle Cooling and breather pipes for car engines

© Ideas In2 Action 2006 Line bending Jigs and formers are used to make accurate bends in the acrylic

© Ideas In2 Action 2006 Plastic coating In industry the plastic powder and the component is electrostatically charged The powder is sprayed onto the component before entering a temperature controlled oven in the case of thermoplastics and a kiln in the case of enamel or thermosetting materials (Note that this process is sometimes referred to as fluidizing)

© Ideas In2 Action 2006 Plug and yoke forming Softened sheet plastic is sandwiched between A male and female mould and left to cool

© Ideas In2 Action 2006 Blow moulding