What Is Plastic Injection Moulding?

in Plastics

Plastic Injection Moulding is the process of injecting heated plastic through a heated barrel, where it is mixed, into a mould cavity where it cools into the configuration of the mould. The process is used to produce both thermoplastic and thermosetting plastic materials.

Alexander Parkes, a British engineer, invented the first artificial plastic in the mid nineteenth century. Naming the material Parkesine, Parkes demonstrated that his creation could be heated, moulded, and cooled, retaining its shape once it had set. Parkesine was a long way from the plastics we know today; it was extremely flammable, expensive, and prone to cracking. Plastics developed over the remainder of the century, although it was not particularly a widely used material until the middle of the next century.

American inventors John and Isaiah Hyatt patented the first plastic injection moulding machine in 1868. The device was extremely simple compared to the injection moulding machines the industry uses today; it essentially pushed plastic through a large, heated hypodermic needle into a mould (or “mold”, as it is spelled in America). The basic process remains the same now, but it certainly doesn’t use a plunger to do it!

James Watson Hendry, another American inventor, created the first screw injection machine following the demand for cheap plastic products created by the Second World War. The machine gave its operator much greater control over the speed and amount of plastic injected into the mould, creating much more usefully designed products, and allowed for mass production. Hendry later developed a gas assisted injection moulding process, which allowed for much larger items, including hollow products because of the much quicker cooling time.

Injection moulding machines today consist of a hopper for the material, a precisely crafted screw or injection ram plunger, and a heating unit. Moulds themselves have been quite expensive to manufacture, so for a long time were used only for products that were to be produced in extremely large quantities to make it worthwhile. Traditionally made from steel and hardened steel compounds; which are still in use today; moulds can now be made from aluminium and much cheaper materials, making it easier to mass produce differently designed items. The cost of the mould is still very high compared to the production cost of the items, so efficiency increases when more items are produced.

Though initially used for much smaller applications such as combs and buttons, plastic injection moulding is now used for many different products in the automotive industry, as well as bottle caps, chairs and tables, musical instruments; pretty much every plastic product available in today’s market.

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Greg Nagell has 189 articles online

Plastic Injection Moulding has been used for many years in different forms to create plastics in industry. Among other methods such as vacuum forming, injection moulding is still the preferred method of plastic production today.

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What Is Plastic Injection Moulding?

This article was published on 2011/11/08