D1-S2-P2-A-Rheologically-optimized
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02.06.2017<br />
1) Screw design:<br />
Theoretical backgrounds: homogeneity<br />
Building of a cold core in the screw channel: Reason for insufficient<br />
appearance<br />
v channel<br />
v circular<br />
v rotat.speed<br />
v circular<br />
active flight<br />
melt pool<br />
conveying direction<br />
cold core<br />
(non sheared material)<br />
contact to the barrel<br />
passive flight<br />
The cold core, which is the<br />
result of the shear flow in the<br />
screw channel and the high<br />
gradient in viscous heating,<br />
needs to be distributed into the<br />
„hot melt“ pool, e.g. by pins and<br />
/ or mixing segments in the<br />
screw design<br />
© Harburg-Freudenberger Maschinenbau GmbH<br />
All rights reserved<br />
Dr. Gerard Nijman: Relaxed Extrusion<br />
June 16, 2017<br />
15<br />
1) Screw design:<br />
Example: Staggered flights<br />
Improved distributive mixing through pin screw with<br />
staggered and normal flights<br />
© Harburg-Freudenberger Maschinenbau GmbH<br />
All rights reserved<br />
Dr. Gerard Nijman: Relaxed Extrusion<br />
June 16, 2017<br />
16<br />
8
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