Plastic moulding method 2 ( blow moulding and extrusion)

-Plastic moulding methods:

-Blow moulding.

-Extrusion.

-Blow moulding:

-process consist following step.

1. In a blow molding hot soft plastic is squeezed into mould.

2. compressed hot air is used to blow a big  bubble  inside a Mould.

3. the plastic swells  out like a balloon until it fills up the whole mould. In this way many plastic bottles, toys are manufactured.

4. blow molding is like injection moulding except that hot liquid plastic pours out of a barrel vertically in a thermoplastic closed end tube.

5. the mould is closed and force how to outward direction to confirm inside shape of mould.

6. After sometime cooling remove the mould.

Hollow part is formed.

Fig.Stages in in blow molding.

-Advantage:

1. Low tool and die cost.

2. complex Hollow shapes possible.

3.high production rate.

-Disadvantage:

1. Hollow shape tolerances hard to control.

-Application:

Example of blow moulding bottle, tubes, containers a, heaters ducts etc.

-Extrusion process:

1. it is continuous process. In this process feeding the Powder of plastic from hopper into the heated chamber.

2. A rotating screw carry  material forward and forces it out through the heated orifice of the die. Orifice carried the shape corresponding to the shape of the final product.

3. After leaving the die product is cooled by water or air blast . And product carried away by help of running belts.

4. Hot plastic is squeezed through a nozzle to making long length plastic pipes. It is also used for make large thick sheets of plastic of fabrication.

Fig.Extrusion moulding.

Advantages:

1. Processes rapid and more economical than any other Process.

2. Very high production rate.

3. It can produce any kind of shape.

4.Material thickness can be  accurately control.

Application:

In a help of extrusion process all thermoplastic material are manufacture. Sheets film, rods , window frames, electrical cable, ropes , pipes , tube, etc.