In the first step, the plastic to be processed is fed into the cylinder in the form of granulate via a hopper. If large quantities are required, the granulate is fed to the hopper via hose lines.

1. The plastic granulate is continuously melted and liquefied with the help of heating bands and the resulting frictional energy on the inner wall of the cylinder. The rotating screw conveys and compresses the melting granulate, constantly pressurising it in the process. This homogeneous, hot mass is then pressed through the extrusion mould.
2. The moulding geometry of the extrusion tool is never actually identical to the cross-sectional geometry of the profile that is to be produced. The mould maker must take into account that the hot plastic melt swells a little after leaving the mould and that the shape and position can therefore change to a greater or lesser extent.
3. To prevent the profile from collapsing, it must be cooled over a certain period of time. Depending on the complexity of the geometry, the profile sometimes travels a longer, sometimes a shorter distance in a cooling medium until it is completely dimensionally stable and true to size. For less complex profile geometries, the profile generally only passes through a water bath to cool down. In the case of sophisticated profile geometries, the still hot profile must pass through a so-called calibration section, in which the walls of the profile are cooled in a controlled manner, but at the same time supported with air or sucked onto cooling fins with a vacuum in order to achieve the required positional and dimensional tolerances.
4. Conveyor belts or caterpillar haul-offs, with which the extruded profile is pulled, ensure a uniform speed of the cooling profile. Fluctuations in speed affect the dimensional accuracy.
5. After the haul-off, there is usually a winding or cutting unit to wind the previously endless profile onto spools or cut it to the desired length.