Today's KNOWLEDGE Share
Any surface particle on a molded part used to belong to the Fountain Flow free surface.
Free surfaces for a visco-elastic material typically suffer from flow instabilities, and these end-up creating surface defects on your molded part. High front velocity and especially flow front acceleration/deceleration will trigger flow instabilities and defects.
This is why the gate area and the end of flow (see picture) are so prone to surface defects. We do have the highest velocity at the gate and a potential extreme velocity at the end of flow (or slowdown due to switchover).
"Tiger Stripes" are a well known defect due to Fountain Flow instabilities triggered by a change of flowfront speed.
source:Vito leo
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