Question

What is fabrication of plastic ? Explain injection moulding process with a neat diagram .

Answer 1

Fabrication is the process in which the prepared resins in the form of granules or powder are converted into desired shape by using various machines or moulds . It transforms the compound materials into finished articles .A proper method has to be selected depending on the shape and size of the resin being used .

Injection Moulding :
1) It is used for thermoplastic resins only .
2) Here ,a predetermined amount of the granular or powdered resin is fed into a heated cylinder .
3) From the cylinder ,the powdered resin is injected at a controlled rate through a nozzle into the tightly locked mould by means of a screw arrangement or by piston plunger .

4) The mould is kept cold to allow the hot plastic to cure and become rigid .After sufficient curing ,the mould is half opened and finished particle is ejected without any deformation .
5) Automation of the entire cyclic process is possible .
6) The method is widely used because of high speed production ,low mould cost ,very low loss of material and low finishing cost .
7) The limitation of this method is large number of cavities cannot be filled simultaneously .
8) Articles prepared by injection moulding are ball pens ,telephones ,buckets ,dustbins ,flower pots ,etc .