注射成形熔体喷射的三维模拟及消除对策研究

Study on Three Dimensional Simulation and Elimination Countermeasures of Melt Jetting Phenomenon in Injection Molding

为了探寻塑料注射成形过程中熔体喷射的消除对策,采用高精度离散格式追踪熔体流动前沿,基于有限体积法离散控制方程,发展了三维数值算法。与实验结果对比发现:所发展算法能有效模拟壁厚为4 mm的长方体型腔内的两种喷射演化模式以及厚壁型腔内的熔体喷射及其演化过程;小壁厚型腔内熔体的屈曲呈二维折叠演化,厚壁型腔内熔体的屈曲呈三维缠绕演化;重力对厚壁型腔内的喷射演化产生影响。通过增大剪切速率即改变熔体流动速度大小或者流动方向能有效消除或抑制喷射现象,并且用两个数值算例论证了该观点。

To explore the elimination countermeasures of melt jetting phenomenon in plastic injection molding,a high resolution discrete scheme was used to track the melt front.The governing equations were discretized by finite volume method and a three dimensional algorithm was developed.Comparing to experimental results,the two modes of molding filling under jetting conditions in the cuboid cavity with 4 mm thickness and the evolution of jetting in thick cavity were successfully simulated numerically.It is found that the jet buckling presents two-dimensional folding in the cuboid cavity with small thickness and three-dimensional roiling in thick cavity.Gravity has an impact on the evolution of jetting in thick cavity.Jetting might be effectively eliminated or depressed via enlarging shear rate with changing the magnitude or the direction of velocity.Two numerical cases were performed to verify the views.