Cast film extrusion melts resin in an extruder and pushes it through a flat slot die onto a highly polished, water-cooled chill roll. The molten web is quenched almost instantly against the roll, which locks in a smooth, glossy surface and very tight thickness control across the web. Because there is no bubble to inflate and stabilize, cast lines can run at much higher speeds than blown film lines, often two to three times faster for a comparable product.
The rapid quenching also means cast film cools before much crystallization can occur, which generally gives it better optical clarity and lower haze than blown film of the same resin. The tradeoff is orientation: cast film is stretched mainly in the machine direction as it's drawn off the chill roll, so it tends to be more mono-axially oriented, while blown film develops strength in both directions. That makes cast film a strong choice for applications where clarity, gauge uniformity, and high-speed converting matter more than maximum toughness.
Cast film is widely used for stretch film, some food wrap, certain lamination substrates, and applications needing very precise gauge bands for downstream printing or coating registration.
Glossary
Cast Film
A film extrusion process where molten plastic is spread flat through a slot die directly onto a chilled roller, instead of being blown into a bubble.
Example
A customer requesting a pallet stretch film with high clarity and very consistent gauge for automated wrapping equipment is often pointed toward a cast film line rather than blown, since cast film's chill-roll quenching gives tighter thickness tolerance.
Nuance
It's a common misconception that cast film is always thinner or always glossier than blown film; in reality both can be made glossy or matte and across a wide gauge range depending on resin and line setup. The real structural difference is the orientation and cooling method, not gloss or thickness by definition.