| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 91 === Abstract
The micro-parts molded by micro injection molding become more and more popular in MEMS (Micro Electromechanical System) applications. Due to the lack of research in polymer melt flow behavior in micro channels, molding process control exists uncertainties. The purpose of this study is to conduct the investigation on the rheological property of polymer melt flowing through micro-channels.
First, the rheological property measurement system design with micro-channels in a mold was established. Sizes of micro-channel of square cross section used vary from 0.5 mm to 0.3 mm then to 0.2 mm. Sodick EH30 micro injection machine together with a mold temperature control unit as high as 250℃ were utilized to conduct the experiments. From measured flow rate and pressure drop followed by a correction in inlet and outlet pressure drop, the viscosity value can be obtained.
Because of the square cross section of the micro-channels, it is necessary to use capillary flow model and slit flow model to analyze the measured data. The calculated viscosity values are found to be very close from both two models (about 2% to 6% difference). Compared with the measured result from traditional rheometer, viscosity values in micro channel are lower and their value decreases with reducing channel size. With, after correct can permit to calculate the viscosity.
Effect of viscous dissipation is expected to have more influence on viscosity when the micro-channel size becomes smaller. After the correction of the viscous dissipation effect, viscosity values are still lower than the value measured by capillary rheometer (lower by about 14% to 38%). This preliminary founding may be of help to the development of micro-flowing simulation and molding technology promotion.
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