Making Plastic Extrusion Products

Extrusion is a manufacturing technique used to form thermoplastic compounds into unremitting products such as sheeting, rods, cast film, tubes, filaments, cable, cord, mono filaments, synthetic fibers, hollow sections for blow molding, compounding, reclaim of plastic pellets, and to coat wire. An extrusion mechanism includes twin screw systems, which are generally used for PVC pipe or profiles and single screw systems, which are used for these and other extruded products.

In this technique, plastic chips or pellets is first loaded and fed into a long heating chamber through which it is stimulated by the action of a continuously revolving screw. At the opposite of the heating chamber the molten plastic is forced out through a small hole or dies with the shape desired in the finished product. As the plastic extrusion comes from the die, it is fed onto a conveyor belt where it is cooled, most frequently by blowers or by immersion in water.

In the process of wide film or sheeting, the plastic is molded in the form of a tube. This tube may be split as it comes from the die and then stretched and thinned to the size desired in the finished film and in the case of wire and cable coating, the thermoplastic is thrust out around a continuing length of wire or cable which like the plastic, passes through the extruder die. The coated wire is wound on drums after cooling.

Applications of extrusion are thin film and sheet extrusions can be used in sealing, packaging, electronics, and other applications, flat sheets are extruded to customer specified thickness and dimensions, rigid pipe extrusion applications can include fluid media transport or custom chemical and unusual strength or dimensional properties, flexible tubing and hose can be extruded with customer specified dimensions, wall thickness, mechanical and chemical properties, tubing can often be made in multilayer and special compound configurations.

Advantages of extrusion are higher potency because of severe strain hardening, dimensional accurateness, good quality finish, economy due to smaller number of process and fewer machining required.