Injection Moulding

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(i) Injection Molding Demonstration Battenfeld HM 40/130 is the machine used in the laboratory session to mold Polypropylene. Thermoplastic materials such as nylon, polystyrene, polythene and polypropylene can be used in a process called injection molding. How injection molding works? 1. The hopper is filled with granules of plastic powder. The hopper stores the material until it is needed. 2. The heater starts heating up the tube until it reaches a high temperature, then a screw thread starts turning. 3. The granules are pushed along the heater section by a motor, which pushes the granules along the heater section. The heater melts the granules until they reach the liquid state. This liquid is then forced under pressure…show more content…
• Polypropylene is available under a variety of trade names, such as: Amco®, Amerfil®, Azdel®, Beamette®, Clysar®, Daplen®, Dexon®, Epolene®, Gerfil®, Herculon®, Lambeth®, Lupareen®, Meraklon®, Mitsui Polypro®, Noblen®, Novolen®, Pellon®, Polypro®, Profax®, Propathene®, Propolin®, Propophane®, Shoallomer®, and Tuff-Lite®. (ii) Moldings Inspection 1) Bubbles: Plastic samples with various imperfections were inspected. In this case, the imperfection is called Bubbles or Blisters. The top right figure shows two different plastic samples, “a” appeared with the Bubbles imperfection, while “b” is how it is supposed to be. Possible causes and cures of the Bubbles imperfection: • Cause: The molten material can become overly fluid when high injection temperatures are used. Thus, air and gases become trapped in the melt stream since the material is now very turbulent due to the high injection temperatures, and these trapped gases will appear in the molded part as voids, as shown in the figures above. Cure: Reduce the injection temperature in order for the material to stiffen, thus the trapped air and gases will escape. • Cause: Insufficient material is a cause of the Bubbles imperfection. There will not be sufficient material to be completely forced into the cavity. Thus, gases will be trapped and for voids which will
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