High web speeds can result in slippage between the film and the treatment roller. In addition to static charges, the result is finest scratches, especially with vapour-deposited metallisation. The scratches destroy the barrier properties of the metal layer and impair the visual appearance. High-speed webs transport air between the roller and the film. This results in an unwanted backside treatment in many cases.
AFS uses nip rollers, avoiding slippage and backside effects. The drive on the corona roll compensates for the increased friction torque. The speed is synchronised to the printing press. The special drive concept of AFS is neutral regarding web tension control systems.
AFS systems can therefore be easily integrated into existing machines. If the drive is to act as an active web tension station, AFS will always install a drive specified or provided by you. This saves space and money.
Foil can only be seal welded where it is not treated with corona. This means that longitudinal and transverse un-treated areas are needed, where any seal welding takes place.
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 web direction can be reached by short pauses in the treatment, the so-called Intermittent. This must be synchronised with the printed image.
AFS controls make it possible to produce these recesses with millimetre precision. The operation is very simple and very comfortable.
Patented ceramic electrode holder
Ceramic electrodes and corrosion protected corona rolls allow the treatment of virtually all common substrates – including conductive ones. Patented electrode holders ensure a particularly long service life of the valuable ceramic electrodes.
Automatic power control
Alternating web speeds require regulation of generator power to deliver a constant corona dose (W min / m²) to the film. Proportional control from AFS handles this automatically for you.
There are special versions available for operation in solvent-containing environments. They work with overpressure in the electrode space. AFS offers them both with and without explosion protection certificate. For certified facilities, however, incur considerable costs due to the enormous technical effort and the expensive acceptance procedure by an accredited body.