Discussion applies Gas Counter Pressure of Co-Injection Molding
| Autor: | De-Wei Liu, 劉德緯 |
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| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 Today there are many types of daily products made by plastic. In order to reduce manufacturing costs, improve product strength and product appearance and to response environmental protection requirements, kinds of green molding techniques are developed, such as: gas-assisted, hydraulic auxiliary, and co-injection molding, etc. Co-injection molding is also known as sandwich molding. Co-injection molding is producing composite plastic product with multilayer structure in single injection. The process is to short shot the certain quantity plastic into the mold cavity, and then inject the core melt to complete cavity filling. In the industry recycled material or plastic with better strength are often as the core melt, so that to reduce costs and increase the product strength. Or decreasing the residual stress by the appropriate quantity in proportion, which also can increase the mechanical strength and surface quality. In this study, we use the gas counter-pressure techniques to enhance the mechanical strength in co-injection molding process, also to reduce the residual stress distribution. Because there would be two different front waves in co-injection molding, cortical thickness and core penetration length are more difficult to control, but the core melt flow is instable due to fountain effect. Therefore, this study applied gas counter-pressure technology in the co-injection molding to suppress the wave front flow behavior. By controlling different amount of gas to discuss the effects of core melt penetration length and penetration area on product strength. Experimental results show that addition of gas counter pressure can effectively increase the penetration stability of the core melt, change the penetration length and area of the core melt, reduce the residual stress and increase product strength. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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