非对称温度场下微孔发泡模内表面装饰复合成型工艺的翘曲变形

以拉伸试验样条为研究对象，采用正交试验设计与流动仿真计算，对非对称温度场下微孔发泡模内表面装饰复合成型工艺（MIM/IMD）中制品翘曲的影响因素进行分析，获取翘曲变形最小的最佳工艺参数组合。并对4种注射成型工艺（MID/IMD、IMD、MID、CIM）分别在X、Y、Z方向的翘曲变形仿真结果进行对比，分析不同成型工艺的翘曲变形在不同方向上的变化、泡孔半径及密度，探究微孔结构及分布对翘曲变形的影响规律。结果表明，熔体温度210 °C、注射速率55 cm³/s、充填体积98 %、超临界N₂浓度0.2 %（质量分数）、冷却时间40 s时，翘曲最小，翘曲变形最大减少3.414 mm；采用发泡工艺对制品的翘曲有一定的抑制作用；非对称温度场导致覆膜侧的泡孔尺寸及密度大于非覆膜侧，且温度较非覆膜侧高，使样条覆膜侧收缩变形慢于非覆膜侧，从而导致样条两侧产生具有向非覆膜侧内凹卷曲趋势的不均衡翘曲变形。

Warpage of microcellular foaming and in?mold decoration combined injection molding under asymmetric temperature field

Taking the tensile test sample as an example， we investigated the effects of main process parameters on the warpage under molding condition of asymmetric temperature field in the process of microcellular foaming and in?mold decoration combined injection molding （MIM/IMD） using an orthogonal experimental design and flow simulation to obtain an optimal combination of process parameters with minimum warpage. The simulation results of four injection molding processes （MIM/IMD， IMD， MIM， CIM） were then compared in the directions of X， Y and Z axis， including the warpage variation in different directions of samples， cell size and density to explore the influence of the microporous structure and distribution on the warpage. The results indicated that the warpage reached the minimum and the warpage decreased by a maximum of 3.414 mm when the melt temperature， injection rate， filling/holding pressure （V/P） switch， supercritical N₂ concentration， and cooling time we set as 210 °C， 55 cm³/s， 98 %， 0.2 wt%， 40 s， respectively. The application of microcellular foaming technology in the injection molding process can facilitate to reduce the warpage of the molded products. The asymmetric temperature field made the cell size and density greater those that in the non?film side. Moreover， the temperature in the film side was also higher than that in the non?film side. This made the shrink of sample in the film side slower than that in the non?film side. As a result， the unbalanced warpage in both sides of the sample tended to concave and curl towards the non?film side.