Shorter Blown Film Die Provides Better Control

A new way to combine layers in a spiral-mandrel die shortens die height by about 5 in. for five- to nine-layer blown film.

A new way to combine layers in a spiral-mandrel die shortens die height by about 5 in. for five- to nine-layer blown film. The improved Lo-Pak die comes from Davis-Standard Corp.’s blown film div. in Somerville, N.J. It combines any minor layer of 5% to 10% of wall thickness (such as barrier or tie layers) with another minor layer before combining the two with thicker layers. The result is a die 31 in. tall vs. 36 in. for the original Lo-Pak die introduced in 1998. The new “confluence” design also reportedly controls shear rate better because critically thin layers have less surface contact with die walls. Layer thickness is said to be more accurate because there is less interfacial instability.