Have you ever wondered how those beautiful plastic goods you see in shops and homes are made? Chances are you have, but never cared to find it out. Plastic is a general term used to refer to materials that can be shaped by raising their temperature until they become pliable and soft for machines to handle.
Technically, plastics that can be shaped by raising its temperature are called thermoplastics.
There are also plastics that cannot be conveniently shaped using heat, and they fall into a different category called engineering plastics. These types are usually shaped using other techniques like turning, milling, honing, grinding, thermos setting…etc. Some of the common thermoplastics are polystyrene, nylon, polypropylene and polythene.
The process of converting thermoplastics into goods is called plastic injection molding. It is called injection because the plastic is converted into an almost-liquid stage and then it is injected by a screw-driven mechanism into a mold capable of providing the shape to the plastic. The machine used is common called Plastic Molding machine. The earliest of machines that were manufactured used human force (they are still in use) to drive the melted plastic into the mold, but these days they have largely been replaced with electric motors.
The choice of machine (human or electric driven) depends on the size of the product one wishes to produce. Small components produced in small quantities don't require electric molding machines. But larger ones though produced in smaller quantities have to be produced only on electric machines because of the large force required to drive the almost-molten material into the mold.
The mold used for forming the goods (or components) is a critical device and requires precision engineering. They are usually made by expert mold makers who have extensive knowledge in metallurgy and shaping. The metal used to make the molds must confirm to precise quality standards like temperature and deformity resistance. They must also be capable of tolerating high thermal shocks.
There is no industry that does not use plastics these days, because they cost very little to maintain (especially painting) and can be made into virtually any shape and color. Yet another advantage is their light weight making it ideal for use in home appliances, aircraft parts, automobile components, computers, cycles, packaging, furniture and many more. In fact there is no industry that does not use it in one way or the other. They have proved to be very useful in substituting for forest produce like timber.
Since the earliest days, the molding industry has come a long way in terms of technological development and the biggest beneficiaries are the defense, sports and computer industry. The armament industry is one of the biggest users of plastic injection molded components in their equipment. Unlike in civilian uses, they prescribe very exacting standards for tolerance and quality.
Component manufacturers therefore use hetero cavity techniques to make defense related plastic molded parts. The technique is widely used for manufacturing components that require high strength, tolerance to high temperatures and low failure rates. They also have wide applications in civilian related products as well.
