A mathematical model for the simulation of the injection
moulding of thermosetting elastomers has been developed. The
model uses suitably reduced forms of the fundamental equations
of continuity, momentum and energy as a basis, with a
constitutive equation to describe how the elastomer viscosity
varies with local flow conditions. A cure model is used to
calculate cure levels during the injection phase, and the time
taken for the final moulded component to reach a specified
minimum cure level during the subsequent cure cycle.
Moulds are defined by splitting the various elastomer flowpaths
into a network of end to end connected geometric entities of
simple cross section, for instance circular, rectangular and
The moulds elements are discretised using a finite difference
mesh and the equations which comprise the model are cast into a
suitable finite difference form for solution. Solution of the
continuity and momentum equations involves numerical
integration using the trapezoidal rule and the energy equation is
solved using a fully implicit Crank Nicholson method, since this
gives unconditional stability. The model also allows for a wall
slip boundary condition.
The flow model has been experimentally validated by simulating
an extrusion rheometer and comparing predicted capillary
pressure drops with measured ones. It has also been validated by
comparing real injection moulding pressure drops with
corresponding predictions. The cure simulation has been validated by comparing predicted
cure times with measured cure times taken during the injection
The effect of the variation of material properties, heat transfer
coefficient and finite difference mesh geometric parameters on
simulated results have been assessed.
The effect of wall slip on simulated injection results has been
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.