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Gas assisted injection moulding: Experiment and simulation. Industrial machine experimental studies of the effect of process variables on gas bubble formation, and with simulation based upon a pseudo-concentration method.

By Leigh Mulvaney-Johnson

Abstract

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

Topics: Gas assisted injection moulding, Simulation, Gas bubble formation, Wall thickness prediction
Publisher: Department of Mechanical and Medical Engineering
Year: 2001
OAI identifier: oai:bradscholars.brad.ac.uk:10454/4983
Provided by: Bradford Scholars

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