Today's KNOWLEDGE Share:Thick parts need more packing

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Today's KNOWLEDGE Share

Why do thick parts need more packing than thin ones ?


Packing changes the parts size/volume/mass, but not the final density. Whatever is already solid at the end of fill (frozen skin) does not need any packing (shrinkage has already occurred !).

So, as the picture shows (in a slightly exaggerated way) in a thin part/section one only has to pack a tiny fraction of the total volume, whereas in a thick part/section, most of the volume will need to be packed, to compensate for the shrinkage.



Since thick parts are easy to fill and need more packing, it is not unusual to use a packing pressure much higher than the filling pressure. Something that might not fit the default values proposed by simulation...

Always think twice before accepting a default value.


Source:Vito leo

Follow: http://polymerguru.blogspot.com



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