What is meant by Fabrication of plastics? Explain injection moulding with the help of neat diagram .
Fabrication of plastic is the technique of giving any desired shape to the plastics by the use of mould. Because of the properties of polymers it is possible to mould them and change their shape using a number of different repetitions manufacturing processes. A proper method is to be selected depending upon the shape and type of resin being used. The most important of these are compression moulding, transfer moulding, extrusion and injection moulding.
This method is only applicable to Thermoplastic resin The moulding plastic powder is fed into a heated cylinder. From there it is injected into the tightly locked mould at a controlled rate by means of a screw arrangement or by a piston plunger. The mould is kept cold to allow the hot plastic to cure and become rigid. When the material have been cured sufficiently, half of the mould is opened to allow the injection of the finished article without any deformation . heating is done by oil or electricity.
1.ADVANTAGE:-This method has high speed production, low mould cost, very low cost of material and low finishing cost. Hence it is the most widely used method for moulding of thermoplastics.
2:-DISAD VANTAGE-Since a large amount of cavities cannot be filled simultaneously, there is limitation of design of articles to be moulded