Today's KNOWLEDGE Share
With glass fibers, shrinkage can be 10X lower in the flow direction than in the transverse direction.
This is the classical driving mechanism for warpage of GF filled compounds and most people will look at the ratio of perpendicular to parallel shrinkage as a sort of Warpage Index.
However, one can easily demonstrate that Warpage does NOT scale with this RATIO, but rather with the DIFFERENCE of perpendicular to parallel shrinkage.
This is crucial, because when you increase packing, you reduce both values (hence, their difference), but barely change the ratio.
And what we observe is that if you double the packing pressure, you roughly cut the warpage down by 50%, despite the anisotropy ratio remaining the same !
Packing is the single most effective way to reduce warpage in GF filled materials.
Credit:Vito leo
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