What is extrusion?
Extrusion is a manufacturing process in which a material is forced under high pressure through a shaped opening (die) to produce profiles of constant cross-section. Think of aluminium window profiles, PVC drain pipes or cable sheathing — almost every product with the same cross-section along its length is extruded.
How does it work?
The principle is simple: the material is pushed through a die, similar to dough from an icing bag. The process varies by material:
- Aluminium — heated to 450–500 °C, then pressed
- Plastics — melted and continuously pressed
- Clay / brick — cold or moist through the die
- Rubber — extruded as a continuous profile
Application
Extrusion is widely used in construction:
| Material | Products |
|---|---|
| Aluminium | Window profiles, façade panels, rails, fittings |
| PVC | Drain pipes, gutters, window frames |
| Polystyrene (XPS) | Insulation boards |
| Polyethylene (PE) | Water pipes |
| Clay | Hollow bricks with vertical voids |
| Rubber/EPDM | Glazing rubbers, sealing profiles |
Aluminium extrusion
Aluminium extrusion is one of the most common uses in construction:
- An aluminium billet is pre-heated
- A ram presses it through a die of hardened steel
- The resulting profile is cooled and cut to length
- It can be finished by anodising, lacquering or powder coating
This produces complex shapes such as hollow window profiles with thermal breaks and integrated glazing rebates.
Extruded polystyrene (XPS)
XPS is an insulation produced by extrusion. It has:
- Higher density than EPS — stronger
- Closed cells — does not absorb water
- Smooth surface — from the pressing
- Higher cost — due to the process
XPS is used for perimeter insulation, insulation under loaded floors and inverted roofs.
Difference from other techniques
- Pultrusion — similar, but material is pulled rather than pushed (especially glass fibre)
- Injection moulding — for variable shapes, no continuous profile
- Rolling — profile forming by rolls, mainly steel
- Profile forging — shaping by impact, not continuous
Advantages and disadvantages
| Advantages | Disadvantages |
|---|---|
| High productivity | High die investment cost |
| Consistent quality | Limited to constant cross-section |
| Complex shapes possible | Cannot vary wall thickness |
| Good material utilisation | Maximum length limited |
Related terms
- Pultrusion
- Aluminium
- PVC
- Plastic
- Profile
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