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#742
Author: David Roisum, Ph.D ,
Email: drroisum@aol.com
Subject: The laminate is curling because of process design physics.
The laminate is curling because of process design physics. The hot LD side will cool and thus shrink, causing a strain mismatch and curl to that side. Reducing the temperature of the LD will probably not be practical, but you could heat the PET to get a small amount of relief depending on the relative temperatures and expansion coefficients. You should also run maximum (near breaking) line tension on the PET, though this may also be of small benefit because the strains caused by temperature are often greater tensile strains. Alternatively, you can reheat and yield the material to decurl or laminate instead of extrude. On page 224 of my Mechanics of Roller book, there are the design equations to avoid curl. All you need to do is add the thermal expansion portion indicated on page 28 to give total strains.
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