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THINGS every one involved in moulding business should know in

INJECTION MOULDING OF PLASTICS - Prabodh C. Bolur

Injection moulding Process involves:

IMPORTANT POINTS FOR FURTHER STUDIES.

  • 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.
  • 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 and 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 and 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 and 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.

Things to know - Polymers

Things to know - Machine

Things to know - Mould

Injection Moulding Process

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Things to know- Machine Injection Moulding Process Screw Plasticating Moulding Key factors influencing proces Shear strain curve
pvt diagram

Thermal stability Balancing melt Flow Balancing Heat Freezing Quality Problems
Three Balances

Moulded-in Stress Shrinkage Inconsistent Dimension Sink-mark Weld-lines
Moulding Problems

CYCLE TIME Plastics Part Design Flow Analysis .. ..
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