Automatic gauge control for blown film is relatively recent. Systems apply differential heating or cooling around the bubble via segmented die lips or a segmented air ring or IBC unit.
Windmoeller & Hoelscher in Germany launched the concept with its NCP (Numeric Control of Profile) die at the K ’79 show in Dusseldorf. The die blew compressed air through channels to cool local areas of its circumference.
NCP dies were installed at three processors in Germany, Switzerland, and Japan, but they weren’t successful in the early years. Various sources attribute the problem to the software, thickness gauges of the time, or a lack of market need for such a high degree of control. Market interest later caught up with the technology as high-speed printing and converting machines required better quality film.
In the mid-1980s W&H revived the idea and introduced the Optifil P1 die at K ’86. The second-generation Optifil P2 system appeared at K ’92. It used heated segments around the die instead of cooling air. The latest, Optifil P3, came out at K 2001. Designed for very high-output lines. It combines a segmented die with a dual-segmented air ring.
In 1988 Reifenhauser and Plast-Control both patented segmented air rings and agreed to share technologies. Reifenhauser launched its DKR dual-chamber air-cooling ring at K ’89. At that show, Kuhne GmbH also showed a segmented air ring with thickness gauges and control software from Octagon GmbH. Gloucester Engineering launched its Autoprofile air ring in 1990. It controls film gauge by blowing heated air through segments of the ring.
In 1995, Addex introduced and patented the first segmented IBC-based gauge controls, which adjust the air gaps of the IBC pancakes.
After W&H’s patent on the auto-gauge die expired in 2000, several more suppliers quickly came out with auto dies. In 2002, Brampton Engineering introduced a segmented die based not on heating the lip, but on deforming it to alter the die gap.
Very few readers of this issue can remember, or even imagine, what it was like when an injection mol...