大型薄壁注塑件型腔内熔体缩痕缺陷形成机理分析及成型参数优化模型的研究

Formation Mechanism Analysis of Melt Sink Mark Defects Inside Mold Cavity for Large Thin-wall Plastic Parts and Parameters Optimization Model of Molding Process

以空调框罩为研究案例,从分析缩痕在模具型腔中的形成及演化机理出发,得出了热交汇差和垂直模具型腔壁厚方向压力值对缩痕形成的影响规律,并验证了垂直型腔壁厚两侧的压力差越大,则缩痕深度越大。结果表明,在熔体温度(T_1)为191.5℃、相对保压压力(P_1)为85.5%、注射时间(t_1)为2.3 s、模具温度(T_2)为33.6℃的条件下,运用遗传算法迭代优化得到了最佳工艺参数组合和最小缩痕指数值为1.352;在优化得到的工艺参数组合下,通过注塑实验和仿真模拟相对照,缩痕深度和缩痕指数实际取值范围分别为0~0.05mm和0.38%~1.43%。

Based on the case study of air-conditioning plane frames,sink mark formation and evolutionary mechanism in a mold cavity were analyzed.Influence of bad thermal intersection and stress along the direction of wall thickness vertical to mold cavity on the formation of sink mark were achieved,and the vertical pressure difference between the both sides of cavity wall thickness was confirmed.It was found that the greater the pressure difference,the deeper was the sink mark.The studies indicated that,with a melt temperature of 191.5 ℃,a relative pressure maintaining pressure of 85.5 %,a mold temperature of 33.6 ℃ and injection time of 2.3 s,the optimum process parameters for the air-conditioning plane frame were achieved by using genetic algorithm and the minimum shrink mark index was calculated to be 1.352.Through a comparative investigation on injection experimental results and simulation values,and the exact value of sink mark depth and the sink mark index should be set to 0～0.05 mm and 0.38 %～1.43 % under the combination of optimized process parameters,respectively.