| Summary: | 博士 === 中原大學 === 機械工程研究所 === 99 === Microcellular injection molding (MuCell) offers many advantages such as melt viscosity and warpage reduction as well as material and energy savings. Despite all of the advantages of MuCell process, the uneasy control of foaming process leading to strip-type flow marks (e.g. bright sliver streaks or swirl marks) on the MuCell part surface hinders MuCell’s wide applications. In addition, foaming quality (skin thickness, average cell size and cell density) can’t be control efficiently is also another bottleneck for MuCell parts. The purpose of this study is to develop a foaming control using the Gas Counter Pressure (GCP) combined with mold temperature control technology during MuCell process and to investigate its relevant influence on parts’ surface and foaming qualities.
The results reveal that under GCP control alone, when the GCP is over 100 bar the surface roughness can be improved by 90%. When GCP increases, the skin thickness also increases, the weight reduction decreases and the average cell size can be reduced to about 30µm. Increasing gas holding time the cell density is decreased and the cell size becomes more uniform. The increase in SCF level also increases the cell density. Applying mold temperature control alone, for mold temperature rangeing between 90~120℃(near Tg), the surface roughness improved by 65%. Increasing mold temperature will decrease the skin thickness, however, the cell size becomes non-uniform severely. Combined GCP and mold temperature control simultaneously, thin skin, small and uniform cell size as well as high surface quality can be achieved efficiently.
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