Presented in
Appl. Math. Modeling, 1994, Vol. 18, June
Page 347
THE
CALCULATION OF SCALAR TRANSPORT DURING THE INJECTION MOLDING OF THERMOSET
POLYMERS
Foluso Ladeinde
SUNY at Stony Book, Stony Brook, NY, USA
H. U. Akay
Technalysis Incorporated
Indianapolis, IN, USA
During the injection mold
filling of thermoset polymers. A finite-element method is presented, with
variations intended to cover a variety of processing conditions. Sample
calculations are presented for the Garcia10 problem and the encapsulation of
a Motorola computer chip. We also share our experience with some of the
peculiar numerical difficulties associated with the simulation of injection
molding for realistic systems. Some of these are related to mesh "quality,"
time step size selection, and (numerical) degeneracy that could result from
some otherwise "physical" material models. The foregoing are issues that
have not received a great deal of attention in the literature.
Keywords: transport,
injection molding, thermoset polymers
Introduction
The process of injection
molding of polymers seems to have benefited greatly from emerging computer
technology. For example, with commercially available computer codes such as
PLASTEC,1 the filling simulation could predict short shots, weld lines, air
trapping, overheating, the number of gates and their locations for optimum
design, balancing of runners, optimization of injection pressure and clamp
force requirements, calculation of pressures, temperatures, shear rate,
shear stress, velocity distribution, etc. Further, postfilling processes
(packing, in the case of thermoplastics) can also be simulated to provide
part shrinkage and the initial state of stress (needed for subsequent
structural analysis of the part).
thin parts arbitrarily
orientated in three-dimensional space which, sometimes, are combined with
full three-dimensional parts, (c) moving fluid front, (d) fountain flow
phenomenon at the front and, finally, (e) fiber orientation, as in
Reifschneider, et al.1 Some examples of numerical simulation of injection
molding include Broyer et al.,2 Hieber and Shen,3 Kamal et al.,4 Wang et
al.,5 Ladeinde et al.,6 and Subbiah et al.7
Most of the computer
simulation capabilities mentioned in the first paragraph have been applied
to thermoplastics and, to a lesser extent, to thermosetting polymers.