
As the bubble moves upward and approaches the nip rollers, it is “pre-flattened” by the A shape collapsing frame. This device provides a smooth transition from a round tube shape to a flattened tube shape. Collapsing frames utilize wooden slats, metal rollers, Teflon-coated rollers, or an air cushion to perform the shape transition. In addition to flattening the tube, the collapsing frame also helps eliminate wrinkles in the final product. These devices can adjustable for both height and entry angle by manual or motorized devices. A pair of nip rollers is located at the top of the cooling tower which called Take off unit or Haul-off unit. Their purpose is to pull the film up from the die. Also, the nip serves as an air seal for the top end of the bubble, so, one of the rolls is rubber covered and next roller is Chrome plated.