Injection Molding Technique For Plastics

Injection molding is a popular method for producing plastic products. A wide variety of goods ranging from small toys to large vehicle parts is made with the help of this technique. It is not limited to produce products of specific areas but commodities of almost all the fields can easily be prepared by injection molding process.

In injection molding process, raw material is in the form of granules of plastic. These plastic chips are inserted into the molding machine with the help of a hopper.  The material is carried forward by a plunger which works by a rotary screw mechanism. The material is led to the chamber in the machine which is fixed at a high temperature. This excessive heat will cause the plastic to melt. This molten plastic is forced into a nozzle by applying high pressure which passes the fluid into the mould of the part to be made. The shape of the mould is opposite to the actual part. The material used for making moulds is either steel or aluminum. It is made carefully to produce exact features of the desired shape by accurate machining. When molten plastic is settled into the mould, it is allowed to cool. After getting cool, the mould is then opened and the part is extracted from it. The properties and strength of the substance can be varied by mixing additional suitable material in the granules before they are entered into the machine.  This material can be any colorant used to give preferred color to the product or it can be any resin for increasing the strength of the part.

In order to get an optimum and efficient result from plastic molding, some controlling factors must be observed. To increase the productivity of the process, the mould is usually kept at a very low temperature so that cooling of parts can be done as quickly as possible. Another way to increase productivity is to change the speed by which material is being injected into the mould. This is usually done by controlling the viscosity of the fluid. A viscous liquid requires more insertion force, thus more pressure due to which speed is reduced. If the speed of the fluid is increased, it will produce more shearing effect in the liquid. Besides that, if the temperature of the molten material is kept at a higher value, the cooling time will increase resulting in a production of thicker items. The material should be used as efficiently as possible so that there is minimum wastage of plastic.

The type of moulds used in the process is one of the major determinants of overall production cost. The cost of a simple mould is much less than the complicated moulds which have fine patterns and cavities in them. The durability of the moulds also plays an important role for cost determination. The long lasting moulds help in reducing the manufacturing cost.

Plastic injection molding has both advantages and disadvantages. One of the greatest advantages is the higher production rate of the process if the same part is to be made frequently. The machines are usually automated and they require less manual work due to which labor cost is reduced. If the raw material is used properly, there will be fewer chances for scrap to produce. Cost of the process often makes it uncomfortable for the manufacturers. The erection of the machine is expensive owing to the use of some costly parts. Moreover, each part requires a separate mould that also amplifies the cost.

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