| Summary: | The gas assisted injection moulding process is an important extension to conventional
injection moulding. Gas assist can be applied in a number of ways, but
here the penetration of a gas bubble through the polymer melt is of interest. A
3D fi nite element implementation of a pseudo concentration method is employed
to simulate the primary penetration of the gas bubble. The wall thickness prediction
is an important result since the extent of bubble penetration is sensitive
to the remaining melt fraction. A number of methods for experimental measurement
are developed to measure characteristics of the gas assisted injection
moulding process dynamics and product. Key process variables, on an industrial
gas-assist machine, were measured and analysed, leading to an empirical model
for wall thickness prediction. Gas delay time and injection velocity are shown to
be most influential in controlling residual wall thickness. Simulation results are
evaluated against the empirical model. The trends observed, for simulation and
experiment, in wall thickness after changes in process variable settings are found
to agree qualitatively. The wall thickness prediction is found to be within 10% of
the experimentally obtained measurements. === EPSRC
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