Plastic Extrusion

Plastic extrusion is a high-volume manufacturing process that yields continuous products with uniform cross-sections. This technique involves melting thermoplastic materials and pressurizing them to force the melt through a die. A rotating screw’s interaction with the barrel walls generates pressure. The die shapes the polymer into a profile that hardens during cooling. Extrusion produces items such as sheet, film, profile, pipe, and wire coating.

The plastic extrusion process begins with filling the hopper with plastic granules, which are often mixed with additives such as colorants and UV inhibitors. The feed throat transfers the granules to the barrel, where they are gradually heated by heaters and friction. The temperature of the barrel varies along its length, with higher temperatures near the die. The screw pushes the molten plastic through the feed pipe and into the die, which has a specific cross-sectional shape.

The extruded profile exits the die and enters a cooling system, which can be air, water, or a combination of both. The cooling system solidifies the profile and maintains its shape. The profile is then cut to the desired length or coiled for further processing. Extrusion shrinkage occurs when the profile contracts as it cools down, which must be accounted for in die design.

Different types of plastic have different properties and melting points, which affect their suitability for extrusion. Some common plastics used for extrusion are polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and acrylonitrile butadiene styrene (ABS).