Engineering Workshop Material Science MECHANICAL THEORY

Injection Moulding Process-Machine, Applications or Products and Defects

Injection Moulding Process-Machine, Applications or Products and Defects: It is a manufacturing process used for producing parts or components by injecting molten material into the mold cavity. Injection molding can be performed with only one of these materials like glasses and most common thermoplastic polymers.

Note: It is applicable for thermoplastic materials only.

Other Aspects of the Injection Moulding Process:

Injection Moulding Machine:

Injection Moulding Process
Injection Moulding Process-Machine, Applications or Products and Defects

The Injection Molding Machine consists of

    1. Hopper
    2. Hydraulic System
    3. Motor
    4. Screw
    5. Heater
    6. Mold

Injection Moulding Process:

    • The spindle of the motor rotates in a clockwise direction which is in conjunction with the gear. Now the shaft which is attached to the gear also rotates which in turn rotates the entire screw due to the shaft of the motor.
    • The Plastic granules are to be poured into the hopper and they will be pass through the chamber due to the rotation of the screw.
    • The thermoplastic molten liquid is pressurized(by the hydraulic system) at outside the Assembly and allowed to travel through a nozzle of small diameter(Dn)[injector] with high velocity and low pressure into the space between the molds.
    • The liquid will fill the mold with uniform compaction among the atoms and thereby density is uniform.
    • After filling the liquid in the mold, by the cooling process, it will be solidified.
    • Any shape and any size of the component can be produced with uniform density.
    • Density can be controlled by varying the pressure in the pressure line and thereby production rate is high and wastage is recyclable.
    • The component can be produced any number of times till it achieves the required shape.


    • The thermoplastic molten liquid has low viscosity and thereby it can flow easily and that indicates that the diameter of the nozzle is small.
    • In the case of thermoset liquids, the viscosity is high and thereby it is difficult to flow and that indicates that the diameter of the nozzle is large so as to avoid the obstruction.

Injection Moulding Products:

The products which are produced are as follows.

    • Kitchen Products
    • Agriculture Products
    • Plastic Buckets
    • Industrial Pump Impeller
    • Water Cooler Parts
    • Medical Products

Injection Moulding Defects:

The 10 Defects are as follows.

    1. Flash
    2. Short Shots
    3. Vacuum Voids
    4. Sink Marks
    5. Burn Marks
    6. Weld Lines
    7. Surface Delamination
    8. Warping
    9. Jetting
    10. Flow Lines

These are the Injection Moulding Defects observed in products produced from Injection Moulding Process.

This is the complete explanation of Injection Moulding Process-Machine, Applications or Products and Defects which are explained in a detailed way. If you have any doubts, you can ask from the comments section.


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