Profile and sheet extrusion is one of the most commonly used transformation processes. The plastic is melted through an extruder by the action of the screw and heaters. Then it is cooled to the desired shape, such as pipes.
Blow molding is used for the production of objects, especially bottles and containers. Other pieces like toys, garden furniture and some automotive parts can be also produced.
The process involves extruding the material into a cylindrical shape called parison. Then the parison is blowed inside the mold cavity, thus obtaining the desired hollow shape.
The blown film extrusion is the most common method of producing films, such as shrink, stretch, etc.
The process consists of an extruder with a circular extruder head through which the raw material forms a tube. As the resin exits through the hole, air is introduced through the inner part to form something similar to a big bubble. This stretches and thins the film, until it cools and is collapsed between two rollers to form a coil.
The cast film process offers some variants to blown film process, and is used for several applications such as thermoforming.
It consists of the extrusion of the plastic resin through a flat die to form a thin film. It is placed on the surface of a cooling roll, the edges are cut and rolled into a coil.
The injection process, together with the extrusion, is one of the main methods for the production of plastic articles.
Injection molding is a semicontinuous process in which plastic is melted in an extruder. With the reciprocating movement of the screw, the material is injected into a mold where it is cooled.
The injection blow molding process is used for producing hollow objects in large quantities such as bottles, jars and other containers.
The process is divided into two stages, the injection and the blowing. In the first step the preforms are produced by injection. In the second ,one the preform is heated and blown into a mold where the final bottle cools.
Rotational molding is a process used for producing hollow plastic objects. It differs from other methods because heating, melting, shaping and cooling stages occur after the polymer is placed in the mold. This has great advantages as the design constraints are minimal. The products have no stress or have no weld lines.