Blown film extrusion is the oldest film manufacturing process. From an annular nozzle emerges molten plastic and forms a 10 – 20 m high bubble. A pair of nip rolls then puts the already solidified tube together. This creates the so-called layflat, which runs down to the winder. Shortly before the two winding points, the blades slit the layflat sideways, resulting in two flat films that are wound up at the same time.
The classic on the extrusion line
The corona pre-treatment lays the valuable foundation for the further processing of the blown film. AFS systems are the classic on the blown film extrusion line and have been covering every need successfully for years and worldwide. The largest machine manufacturers rely on the reliability of their systems and the proven service provided by AFS. The ease of use and robust design make your AFS system a reliable part of your extrusion line. For example, the system is protected against thickening of the film by simply swinging the complete electrodes away.
Blown film extrusion and corona
The corona treatment of blown film is in the simplest case, directly after the flattening of the freshly extruded tube. So you get two rolls of one-sided treated flat film. However, many applications require two treated sides of the film, e.g. if printed film is to be laminated.
Four-sided pre-treatment on the blown film
Therefore, the second side must be treated before winding. Many untreated blown film types can only be activated poorly or not at all after storage.
AFS offers different concepts for different extrusion line layouts:
- Two two-sided corona stations treat all four flat film sides after slitting.
- A two-sided corona station treats the two outer sides of the layflat before slitting. Two one-sided systems treat the two inner sides of the hose after slitting and before winding.
With both concepts, you can also activate the outer and inner surfaces to varying degrees.
AFS systems for blown film extrusion
Film can only be heat sealed where it is not treated with corona. This means that in both machine and cross- direction, untreated areas are needed where sealing operations are required.
Strip Treatment in Machine direction:
For this purpose, the electrode is equipped with segments that can be folded away. This creates untreated strips on the film.
Skip Treatment in the Transverse or Cross-Direction
Un-treated areas transverse to the machine direction can be obtained by short pauses in the treatment, the so-called Intermittent. This must take place synchronously with the printed image.
AFS controls make it possible to produce these recesses with millimetre precision. The operation is very simple and very comfortable. The robust design, excellent accessibility and ease of use ensure years of trouble-free corona treatment in continuous operation.
AFS quality pays off.