Today's KNOWLEDGE Share:FROZEN SKIN
Today's KNOWLEDGE Share:
The frozen skin that develops during fill will barely subsequently shrink, since it is already solid !
As a consequence, thin parts, where the frozen skin represents a significant fraction of the thickness, will shrink way less than thick parts where frozen skin is a negligible fraction of total thickness!
Note that since frozen skin is highly fill-rate dependent, when filling slowly you will observe less shrinkage, hence less need for pack.
The IMFLUX process (low pressure molding) does indeed claim essentially no need for a pack.
While this is true, please note that filling as slowly as possible (near 100% frozen skin at end of fill, just before risking a short-shot) means that you will produce VERY ORIENTED plastic parts with :
- very high birefringence (amorphous)
- very anisotropic mechanical properties (semi-crystalline).
Many technical parts would rather benefit from low molecular orientation and maximum isotropy of performance, hence a faster fill followed by the appropriate packing is often a better choice.
source:VITO LEO
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#injectionmolding #injectionmoldingmachine #frozenskin
#fillrate #shrinkage
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