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Plastic The term plastic refers to a wide range of polymers which could be moulded. The classification of plastics depends on their polymer chain, production methods, degradation process, composition etc. The development of plastic started as early as 1800 when Charles Good Year invented Vulcanization process; further advancement in chemical process increased the production of plastics. Due to relatively low cost, ease of manufacturing, versatility, and imperviousness to water, plastics are used in a vast and expanding range of products, from paper clips to spaceships. Injection moulding In 1946, American inventor James Watson Hendry built the first screw injection machine. Injection moulding process uses thermoplastics and thermo setting plastic material as raw materials for making plastic. The injection moulding process requires use of an injection moulding machine, raw plastic material, and a mould. Plastic is melted in the injection moulding machine and then injected into the mould, where it cools and solidifies into the final product. Process cycle It takes less than 2 minutes to complete the process and comprises of four stages namely clamping, injection, cooling and ejection. The excess material is cut off after injection moulding process to acquire the correct shape. Materials that are commonly used in Injection moulding process are: Acetal – Used to make bearings and plumbing materials. Poly Carbonate – Used for making automotive panels and parts. Poly Etherimide- Used for making electrical Components. Polystyrene – Used for packaging cosmetics and pens. Poly Ethylene – Used for Kitchen ware, covers, and coatings. Defects occurred during Injection moulding process When injection pressure applied is too high, flashes can occur in the final product. When the cooling rate is non-uniform warping can occur. Bubbles would be formed in the plastic moulded material if the injection temperature is too high or if excessive moisture is present in the moulding material. Unfilled sections could be formed if the flow rate of the material is too low. Sink marks and ejector marks are other defects that are seen if the cooling time is short. Advantages of Injection moulding process Injection muddling process can be fully automated to save time and labour cost. The left over material could be ground and reused hence ultimately there is less wastage. More than one material could be used in collaboration for making a mould. Injection moulding process requires very less post production work as resultant product needs very little finishing work. Injection method is suitable for large scale production as well as small scale and is design flexible. Disadvantages of Injection moulding process In case of large scale production high initial equipment investments and high start up and running costs will occur. Parts must be designed for effective moulding; accurate cost prediction for moulding job is difficult. Application of plastics made through Injection moulding process Plastic made by this process are used in making containers of various sizes and shapes. Other applications are in making bearings and plumbing materials, for making electrical components, in cosmetic industry for packaging, in stationary markets for making pen and other necessities. In automobile industry they are used for making panels and parts for vehicles. Pacific Rim Enterprises Inc. is a specialist in metal casting and forging. He is associated with Pacific Rim Enterprises Inc. He can be reached at info@pacriment.com For more details, contact Pacific Rim Enterprises Email: info@pacriment.com Phone: (800) 928-9108 Fax: (516) 797-1819 Website: http://www.pacriment.com/
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