Plastic extrusion is a manufacturing process in which raw plastic materials are heated to their melting points and formed into continuous profiles. This process is ideal for high volume production, and can be used to make a wide range of extruded plastic products, from tubing and weather stripping to fence panels, plastic films, and wire insulation.
Plastic Extrusion Process
To create extruded plastic products, raw thermoplastic resin (in the form of small beads) is gravity fed from a hopper into the barrel of an extrusion machine. The plastic material then enters the machine itself through an opening called the feed throat, and is forced by a rotating screw mechanism through a heated barrel. In the barrel, the material encounters temperatures above its melting point (anywhere from 392°F to 527°F, depending on the material), and gradually reaches a molten state as it traverses the barrel. Additives, including colorants, UV inhibitors, and others, can be added to the thermoplastic resin prior to it being added to the hopper. Reaching the end of the barrel, the molten plastic travels through a screen which removes any contaminants and unmelted materials. High pressure is used to force the material through the screen. Pressures in excess of 5000 psi are common in this stage. After screening, the still-molten plastic enters a die that gives it the shape of the end product. Die design is critical, as the plastic must flow evenly from a cylindrical profile to meet the product’s profile shape. Uneven flow can create unwanted stresses that can damage equipment and cause warping as the finished product cools. Nearly any shape can be created by plastic extrusion. When the extruded plastic product exits the die, it must be cooled. This process is commonly expedited by the use of a sealed water bath under carefully controlled vacuum that helps the cooling plastic retain the desired shape.
Extruded Plastic Manufacturers & Services