| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 103 === The thick-walled injection molded parts existed numerous defects, including appearance issues, like as the surface sink mark, jetting mark and bubbles. And the longer cooling time always influenced the efficiency of mass production. The appearance issues are mainly caused by the large cavity space and the shrinkage of the melt solidification. The longer cooling time was caused by the poor thermal conductivity of plastics. The heat is hard to dissipate from the internal of the thick product to outside. This study takes 12 mm optical lens as an example. The multilayer structure was adopt to form a B-A-B structure (like a sandwich) of injection molding. Layer A was the first layer, injection molding with cavity A. After layer A solidified, remove layer A to cavity B and the upper and lower layers were injection molded simultaneously. By changing the thickness ratio of layer A and layer B, explore the efficiency between the cooling time and the optical properties to reduce the cycle time and improve the injection molding defects.
This study will explore the optimum thickness ratio is Hi-1=2×Hi (i=2~N) with multilayer structure and reducing cycle time. That is, the thickness of (i-1) layer is twice as (i) layer. And how many layers have to be divided was depend on the sink mark, jetting mark, bubbles and other issues of the individual layer injection molding
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