成形加工
Online ISSN : 1883-7417
Print ISSN : 0915-4027
ISSN-L : 0915-4027
論文
冷却速度制御による精密射出成形法の開発 第2報 各種樹脂で成形した円筒形状部品の収縮特性
今泉 賢小川 瑞樹北山 二朗横井 秀俊
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2013 年 25 巻 1 号 p. 37-45

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In this study, we applied our new process "precision injection molding by cooling rate control" to cylindrical products and investigated the shrinkage mechanism of various resins. With this method, the molded product is rapidly cooled, after which the parts requiring accuracy are left inside the mold and cooled locally to control shrinkage. We particularly focused on the four factors, initial mold temperature, cooling method, cooling time, and time waited for rapid cooling to investigate their effects on shrinkage characteristics. For resins whose glass transition temperature (Tg) was below room temperature, shrinkage control effects could be obtained from this molding method when the initial mold temperature was above room temperature. On the other hand, for resins whose Tg was above room temperature, shrinkage control effects could be obtained only when the initial mold temperature was above Tg. When below Tg, our new method was not better than normal molding methods. Moreover, when the initial mold temperature rose by more than about 70°C above Tg, the temperature differed according to the method used for cooling the molded product. Shrinkage could be controlled better when the molded product was rapidly cooled from outside the mold than inside the mold. With PA 66 and PBT, shrinkage could be controlled by extending the cooling time. This may be because the thermal stress occurring during cooling decreases with time. Furthermore, we found that extending the starting time of rapid cooling further improves the crystallinity of PP. These results clarified that our new method promotes crystallinity at moderate cooling, and controls shrinkage by rapidly cooling the molded product to improve accuracy.

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© 2013 一般社団法人 プラスチック成形加工学会
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