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What Is Plastic Extrusion & How Do I Find Extrusion Companies?

View this video of a pipe extrusion line - Video courtesy of AMUT Group (represented in the UK by Renmar)

Plastic extrusion is a high-volume process where plastic material is melted, and extruded continuously through a tool (die) that forms a particular design of plastic profile, film, tube or sheet in a continuous length, before being cut to the required size.

More complex products can be manufactured using a process called co-extrusion. Co-extrusion involves multiple materials being processed by adjacent extruders and combined while still in a semi-molten state.

The tools contain no moving components and are therefore cheaper to manufacture than some other processes.

Example products are window profiles, pipes, tubes, and films for packaging applications.

Visit here to contact the leading UK manufacturers that can provide you with advice and quotes for your plastic extrusion project.

What are the Different Plastic Extrusion Processes?

Pipe & profile
A horizontal extruder passes molten material through a die mounted at its output end. The material is partially cooled as it passes through the die head, enough to retain its shape. The continuously extruded material is pulled through an elongated water bath or similar device that completely cures the plastic before it is cut to length or wound into a coil.

Sheet/film extrusion
The extruded material is fed through in-line dies that convert the tube of solid molten plastic into a flat and thin planar flow of material. This material is then passed through a series of water-cooled rollers called calendar or chill rolls. As well as removing heat, the rollers are used to determine the thickness of the sheet or film. A film is often measured in microns of thickness, whereas a sheet is measured in mm.

In cases where a more technical solution is needed, e.g. for microwaveable food containers, several layers of different material grades are co-extruded and combined.

Blown film extrusion
On exiting the extruder, the material is usually channelled vertically through a circular die that forms a tube of semi-molten material. The tube is then inflated with air while being simultaneously drawn upwards by rollers, which stretches the film and produces the required wall thickness. As the film continues to cool, it is drawn through several sets of nip rollers to flatten it into ‘lay-flat’ tubing, which can then be spooled or slit into two or more rolls of sheeting.

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