common injection molding defect analysis and solutions--shrinkage

As the part’s volume shrinks, the surface material at the thick wall is pulled in. Shrinkage is the most adverse problem on the surface of plastic enclosure, which mostly. Generally, if the pressure drops, shrinkage possibility will be larger.


When the injection mold is designed, it should consider removing unnecessary thickness. Generally, it is necessary to make the wall thickness even as far as possible.


 If the molding temperature is too high, the thick wall, the rib or the convex side is prone to shrinkage. This is because the parts that are easy to cool are solidified first, and the raw materials of the parts that are difficult to cool will move to that direction. Try to control shrinkage in the places that do not affect the quality of the finished products.


Generally reduce the molding temperature, mold temperature to reduce the shrinkage of raw materials, but is bound to increase the pressure.


Shrinkage Tabel




Injection 

Machine

Short injection time (when the GATE is not solidified, the pressure holding will end)

Holding pressure low

Measuring less

The pressure holding position changes too fast

Injection pressure low

Slow injection speed

Short cooling time

High raw material temperature

Check valve is broken

Nozzle deformation (pressure loss) or overflow

Mold

High mold temperature

Uneven mold cooling

GATE is small

Mold structure design

Improper ejector

Raw Material

The shrinkage of raw materials is large



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