Injection moulding Process involves:

IMPORTANT POINTS FOR DETAILED STUDIES.

• Understanding cavity pressure profile and pvT diagram and Wander - Wall’s equation.
• Understanding of melt flow characteristics.

• Softening / melting of plastics granules, (Screw plasticising)

• Screw design is responsible for consistent quality of melt production.
• Consistency of raw material is also important.

• Dosing of the plastic melt,

• Precise dosing controls can be achieved by well designed m/c controls.
• 3 steps of RPM controls and 3 steps of back pressure control are useful for ensuring precision.
• Understanding of screw plasticising is essential.

• Injection of melt in a closed and clamped MOULD.

• Clamp force should be 20% more than the cavity pressure to prevent opening of mould during injection.
• Melt must flow in balanced manner and fill mould uniformly to avoid moulded-in stresses, which causes in failure of parts in use.
• Understanding of flow pattern is very important while finalising part design.
• Mutisteps Injection speed ∓ pressure control on machine are helpful.
• Understanding of cavity pressure profile and pvT diagram is most essential.
• Understanding of injection speed and pressure during filling phase ∓ pressure phase is very important.

• Cooling time allows melt to freeze and retain the shape of space between core and cavity.

Well designed cooling system in mould ensures.

• Uniform mould surface temperature which is very essential for avoiding warpage and dimensional accuracy. This can be achieved by balancing of heat in ∓ out of the mould.
• Turbulent water flow through cooling channel is desired for efficient heat exchange in the mould.
• Understanding heat exchange in mould is essential.

• Ejection of solidified part after the mould is opened sufficiently

• Understanding of various ejection mechanisms in mould is required.