Manufacturing plastic films involves stretching them at controlled temperatures to produce the desired orientation. Thermoplastics and thermosetting plastics differ in that the latter remain in a permanent solid state after curing. This curing process forms an irreversible chemical bond, and thermosetting plastics break down when heated instead of melting. A variety of plastic manufacturing processes have been developed to cover a wide range of applications, part geometries and types of plastics.
If the film has an uneven thickness or solidification, the bubble will be asymmetric and the thicker side of the bubble will not expand as much as the thinner side, resulting in an irregular film gauge throughout the band. To produce higher performance films or reduce thickness, manufacturers of shrink films are looking for resins that allow them to do so. There are two general categories of shrink film: specialized shrink film produced by some additional orientation process and industrial shrink film produced by manufacturing conventional blown film. Compact desktop 3D printing systems for creating plastic parts are becoming increasingly accessible and require no special skills, allowing professionals to accelerate iteration and production cycles.
Blow molding is a manufacturing technique used to create hollow plastic parts by inflating a heated plastic tube inside a mold until it takes on the desired shape. CNC machining is a subtractive process in which the material is extracted using a rotating tool and a fixed part (milling) or a rotating part with a fixed tool (lathe). Shrink film is manufactured by orienting the bubble in both directions and then freezing the stressed molecules, freezing the film as quickly as possible. The density of foam can be controlled and a wide range of foams can be manufactured, from thin films to thick blocks.
Biaxially Oriented Polyethylene (BOPE) films are used solely as shrink film applications, with different layer structures, recipes and process parameters. To make a blown film, air and plastic are blown through heated tubular chambers of different diameters to create a thin film that is then cooled and transferred to the rollers. Although three types of materials are used in flexible packaging: paper, thin-gauge aluminum and plastic, plastic films are in more demand than the other two materials combined. Softer thermosetting plastics require specialized tools to support the parts during machining, and filled plastics can be abrasive and reduce the life of the cutting tool.