Film blowing machine

A film blowing machine involves one process used to make plastic film. Extruded tubular processing is most often used with polyethylene films but can be used with other polymers. The film may be laminating film, shrink film, agricultural covering film, bags or film for textiles and clothing, and other packaging materials. Parts include: screw and barrel, motor, inverter, heaters, die head, winder, and tower. The main motor may have frequency control of motor speed to improve speed regulation and save electricity. The screw and material barrel may be made from a nitrogen-treated chromium-molybdenum-aluminum alloy. At the beginning of the process, the polymer comes in the form of a pellet. it is heated and melted into a viscous liquid between rotating screws and barrels of the extruder. This allows for the polymer to be fed through a die that shapes it in the form of a tube. This tube is then carefully inflated, so there is no risk of tearing, into a bubble by injecting it with air. The bubble is simultaneously being cooled in its interior, via a cooling system, and on the exterior surface, through the use of an air ring, to solidify the material. A set of collapsing frames or guides are then used to collapse the bubble into two, more defined, layers within closer proximity. Now that the layers are close, a series of nip rollers flatten the layers together to form a two-layered plastic film that is then wound onto a cylindrical roll for packaging purposes. This process may vary depending upon the specifications and models of the machines. In the case that the bubble formed from air injection is not handled with caution, the bubble may become unstable and deform in a number of different ways. Draw resonance exists when the film velocity at which solidification occurs is much higher than the velocity of the melted liquid as it exits the die. This causes the melt to stretch too quickly and the bubble diameter starts to vary along its surface. One way to fix this situation is to increase the speed of the melt through the die.