1. Plastic granules are placed in the hopper. They then fall through the hopper onto the Archimedean screw.
2. The screw is rotated via the motor and gearbox. This forces the polymer forwards towards the heaters where it becomes softened to the point where it is ready to be injected into the mould.
3. Hydraulic ram forces the softened polymer through the feedhole into the mould. Pressure from the ram ensures the mould cavity has been filled.
4. When sufficient time has passed to allow the polymer to cool and solidify, the mould halves are opened and the product is removed. As they open, ejector pins are activated to remove the product from the mould.
5. Once emptied, the mould is closed ready to begin another cycle.
- can produce complex 3D shapes, high volumes can be produced with consistent quality
- initial set up costs are high, moulds are expensive
USES - Toys, TV cases, car dashboards
1. A tube of heated & softened polymer is extruded vertically downwards. This tube is called a Parison.
2. Mould halves close, trapping the polymer at the upper end, effectively sealing it.
3. Hot air is blown into the Parison, forcing it out to follow the shape of the mould.
4. Mould effectively cools the polymer, allowing it to be released from the mould.
5. Mould halves are opened & product is extracted.
- rapid method of producing hollow objects with narrow necks (bottles), non circular shapes can be produced
- moulds can be expensive, difficult to produce re-entrant shapes (shapes that do not allow easy extraction from mould, for example a dovetail joint), triangular shaped bottles are difficult to produce
1. Moulds are loaded with a precise amount of thermoplastic powder before being clamped together.
2. Moulds are rotated about the arm spindle and the whole arm is rotated towards a heated chamber where the thermoplastic is heated to its melting point. The continuously rotating mould ensures the thermoplastic covers all of the mould.
3. Next stage is the cooling chamber where the material is cooled ready to be extracted from the mould.
4. Mould is returned from the starting point where mould halves are separated and the product is removed.
- ideal for rigid, tough & flexible shapes, large range of sizes is possible, surface textures can be applied to finished products from textures applied in the moulds, cheaper moulds
- only hollow shapes can be produced
USES - Flower pots, footballs
1. Thermoplastic powder is placed in the hopper. Powder falls onto rotating Archimedean screw, which pushes material towards a heated section of the extruder.
2. Heaters soften the plastic, which is then forced through the die by the rotating screw.
3. On exiting the die, the plastic product is then cooled using a water jet.
4. Product is cut to the required length.
- extrusion has the advantage of generally being a low cost process that requires only simple dies
- can only produce continuous cross sectional shapes
USES - Curtain rails, window frame sections, guttering
1. Rollers are heated to just above the softening point of the thermoplastic.
2. During the rolling process, plastic 'dough' is forced through the gap roller. Rollers determine thickness of the material.
3. Final roller is the 'chill' roller that cools the material.
1. Preformed 'slug' (compressed powder) of material is placed between the 2 halves of the mould.
2. Mould is heated to a temperature that will allow the cross links to form within the material.
3. Mould is closed onto the preform & pressure will force out any excess material. Moulds are held close under pressure at required temperature to allow the material to be cured.
4. Mould is opened. Product can be ejected while it is still hot.
- moderately complex parts can be produced over long production runs
- low start up costs & little waste material
- necessary to manufacture a preform, process is restricted to products with low complexity