31-01-2013, 04:48 PM
CRITIQUE OF OUR MOLD-FILLING CALCULATION
1CRITIQUE OF OUR MOLD.pdf (Size: 1.59 MB / Downloads: 328)
Our calculation was fairly nasty, yet we made so many assumptions that
the calculation is useless quantitatively.
Assumptions:
1. Constant volumetric flow rate - otherwise keep time derivatives in the
three Navier-Stokes Equations.
2. Negligible pressure drop in gate
3. Newtonian - Polymer melts are not Newtonian! This assumption keeps
the three Navier-Stokes Equations linear.
4. Isothermal - This is the worst assumption. Actually inject hot polymer
into a cold mold to improve cycle time. To include heat transfer,
another coupled PDE is needed! The coupling is non-trivial because
during injection, a skin of cold polymer forms on the walls of the mold
and grows thicker with time.