吹膜製程側邊入料式螺旋式心軸模頭最佳化設計

Abstract

在押出吹膜製程中，側邊入料式螺旋式心軸模頭可改善中心入料式心軸模頭的缺點，使得使用此種模頭來從事吹膜生產的塑膠加工廠可以增加產量，而且可避免產品外觀不良及產品翹曲的問題，尤其是當多層膜的層數增加使用此種側邊入料式螺旋式心軸模頭不會有材料裂解導致物性下降之虞。而且此種模頭本身體積較小，相對也會減低模頭本身的成本，且在更換模頭時或者是卸下模頭清料時均較為方便且省時，因此近年來在國外廣受重視。側邊入料式螺旋式心軸模頭分為進料溝與螺旋溝兩部分，共計有十一個設計參數:進料溝有分段點高度HBC、起始溝深、起始溝寬、螺旋角;螺旋溝有起始溝深、起始溝寬、區段數、溝道數、螺旋角、心軸傾斜角、內外模頭間隙。有本文將採用二維控制體積法（Control volume method）的流動模式，以等溫非牛頓流體去分析此模頭中膠料在入料溝道區及螺旋溝道區的流動行為，同時並配合田口法去分析以便快速找出模頭在此部分的最佳幾何形狀，以及考慮非等溫的條件下，模擬整個模頭的流動情形。

Abstract Side-feed spiral mandrel die was designed to overcome the disadvantage of central-feed spiral mandrel die. The production rate can be improved and the possibility of forming the poor surface appearance and the warp problem can also be avoided using this type of die. Especially, the possibility of material degradation, which causes the decrease of mechanical properties, can be eliminated via this type of die when the layers of film increase. In addition, this type of die possesses the characteristics of small metal body, which results in a decrease of die cost, and easily taking apart of the die or changing the processing material. Recently, this type of die, thus, has attracted the attention of the foreign equipment suppliers. Therefore, this thesis first employees a flow model of two dimensional control volume method to simulate the flow behavior in the side-feed and spiral mandrel sections. Under this circumstances, the non-Newtonian fluid is assumed to be in the isothermal condition and the flow behavior in these sections will be simulated. In addition, we use the Taguchi method to search several optimal sets of die geometric parameters by assessing the flow uniformity and mixing degree. Finally, under non-isothermal condition, the geometry of die will be extended. This will allow us to simulate the flow behavior and performance of entire die.