Plastic Process Essay

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Methods of Processing Plastic There are a variety of methods used to process plastic. Each method has its advantages and disadvantages and are better suited for specific applications. These methods include: injection molding, blow molding, thermoforming, transfer molding, reaction injection molding, compression molding, and extrusion. The main method used for processing plastic is injection molding. With this process, the plastic is placed into a hopper. The hopper then feeds the plastic into a heated injection unit, where it is pushed through a long chamber with a reciprocating screw. Here, it is softened to a fluid state. A nozzle is located at the end of the chamber. The fluid plastic is forced through the nozzle into a cold, closed mold. The halves of the mold are held shut with a system of clamps. When the plastic is cooled and solidified, the halves open and the finished product is ejected from the press. Blow molding is used when the plastic item to be created needs to be hollow. A molten tube is created with blow molding by using compressed air, which blows up the tube and forces it to conform to the chilled mold. Variations of blow molding include injection, injection-stretch, and extrusion blow molding. With injection blow molding uses a perform, which is taken to a blow mold and filled with compressed air. As a result, it conforms to the interior design of the blow mold. With injection-stretch blow molding, a the plastic is stretched prior to being formed. Otherwise, it is essentially the same as the injection process. With continuous-extrusion, a molten plastic tube is continuously created. At the appropriate times, the tube is pinched between two mold halves. Then, a needle or a blow pin is inserted into the tube and blows compressed air up the part in order to force it to conform to the mold interior. With

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