The Auto Air ring automatically corrects thickness by controlling air blow temperature in segments in response to thickness data from the bubble circumference that is constantly measured and fed back. Inside the air channel of the ring are arrayed 60 -- 120 (i.e., 80 heaters for 350mm diameter die) heaters in a donut configuration; film thickness is corrected by individually controlling the temperatures of the heaters. For example, if the charge to a heater that corresponds to a thick area of the product is increased and the air temperature rises accordingly, that section of the bubble is elongated more, thus thinning the film. This air ring is an indispensable component for forming high quality film at high speed such as masking films and films for multi-color printing.
Taking a 50 μm-thick film as an example, manual adjustments can correct thickness to ±6 -- 7%, but, in actual mass-production,
thickness fluctuations can be as much as 8 -- 10% because of changes in room temperature, size changeovers, etc. The Auto Air Ring keeps accuracy within ±5% at all times.
*Numerical figures will differ according to the type of resin and molding conditions.
In contrast to thickness control by the gap between lips of the die or the die temperature, an ununiform thickness can be corrected accurately and swiftly regardless of the blow-up ratio.
Even after thickness correction, the amount of bubble resin and air flow on the circumference remain constant, so the bubble retains its shape and film does not incur sagging or other issues, thus operators enjoy stable forming.
Numerous tiny, high performance heaters are arranged around the circumference to enable minute localized thickness corrections anywhere along the circumference.
The time required to start up production and change over to different sizes can be reduced (generally by 10 -- 15 min). Moreover, profiles are stably reproduced owing to memorized settings.
Because of the improved thickness accuracy, films can have a smaller average thickness. Materials costs can be reduced anywhere from 6 -- 10% in some cases. Moreover, the improved thickness accuracy translates into reduced scrap loss in downstream processes, such as printing, etc.
The Auto Air Ring has a simple structure with no mechanical movement, thus is highly durable. Should a heater disconnection occur, it can be easily replaced from the outside. Moreover, it does not require any adjustments, is easy to operate and needs hardly any maintenance.
The Auto Air Ring can be easily retrofitted to existing production lines, making its introduction costs less than other types of systems.
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