熱塑性塑膠射出成型之噴流現象研究

Abstract

本研究之目的在於建立可模擬塑膠射出成型時的噴流現象之數值分析流程，分析使用的軟體為廣泛應用於流體變形行為模擬之商用套裝軟體Flow 3D。利用軟體Table Curve 3D，將原始的Cross WLF黏度模型轉換為Carreau 黏度模型以便於處理射出過程之塑膠原料的黏度變化。模擬中針對四種參數澆口厚度、澆口速度、進料溫度及模具表面粗糙度等探討其對噴流現象的影響。 模擬結果顯示塑膠在通過澆口部時，由於受到模壁的剪應力作用，會使得靠近模具壁之塑膠的溫度比前端的溫度高，且溫度高的塑膠有往澆口側回流的趨勢，容易造成捲氣的情況。此外當射料溫度較高時，模具表面粗糙度對噴流的影響取決於澆口速度大小。澆口速度小於2 m/s，隨著模具表面粗糙度的增加，離開澆口的塑膠流之長/寬比值會減少；澆口速度大於4 m/s以上時，隨著模具表面粗糙度的增加，離開澆口的塑膠流之長/寬比值有增加的趨勢。

The purpose of this study was to establish a mathematical model for analysis of jetting phenomena occurred in injection molding of thermalplastics. In the analysis, the widely ued software Flow 3D was selected for simulation, in which the Cross WLF viscosity model was transformed to the Carreau viscosity model by Table Curve 3D software. Four parameters, namely, gate thickness, gate velocity, resin temperature and mold surface roughness were chosen for study its effects on the jetting in injection molding. The results showed that the temperature of the polymer near the mold wall was higher than that in the front, this phenomena may arise from the shearing stress between the mold wall and polymer flow polymer. In addition, when the material temperature was high, the effect of the mold surface roughness on the jetting was dominated by the gate velocity. When the gate velocity is smaller than 2 m/s, increasing the mold surface roughness caused the polymer flow length/width ratio to reduce. When the gate velocity was faster than 4 m/s, increasing the mold surface roughness would cause the polymer flow length/width ratio to increase.