A one-of-a-kind pre-stretch line for blown film collapses the film bubble, blocks it flat, and then stretches it five times without preheating.

A one-of-a-kind pre-stretch line for blown film collapses the film bubble, blocks it flat, and then stretches it five times without preheating. The film is pulled between five pairs of compression rollers, each turning up to 25% faster than the preceding pair. Macro Engineering & Technology Inc., Mississauga, Ont., built the line six years ago for an unidentified U.S. processor of pre-stretched film for handwrap. Macro patented the process two years ago (U.S. Patent #6413346 B1). Two or three stretches are typical of cold drawing, but Macro believes the five-stretch series is a record. The two-ply film is stronger than a single layer and allows more downgauging without breaking. The line can also bypass some rollers and run with only three draws.