厚壁结构聚碳酸酯制品注射成型的典型缺陷与控制

Control of Typical Defects in Injection Molding of Thick-Walled Polycarbonate Products

采用单因素多水平的试验方法,考察了注射成型工艺对厚壁结构聚碳酸酯制品的典型缺陷(表观缺陷、几何收缩和残余应力)的影响,工艺条件包括模具温度、注射速度、保压时间、保压压力和冷却时间。通过制品表观质量、收缩状态和应力分布的表征,分析了不同缺陷的变化规律。结果表明,表观缺陷中的真空泡在模具温度120℃以上、保压时间20 s、冷却时间60 s时基本不存在,而表面气痕在注射速度低于5 mm/s时完全消除。随着保压压力、保压时间和模具温度的增加,制品几何收缩显著降低,尺寸精度和几何变形得到有效控制。制品的残余应力受成型工艺的影响,但退火处理的影响更加明显,也是降低残余应力的有效手段。

The influence of injection molding process on the typical defects(apparent defects,geometric shrinkage and residual stress)of polycarbonate(PC)prducts was investigated by the test method of single factor and multi-level,and the process conditions were as follows:mold temperature,injection speed,holding time,holding pressure and cooling time.The variation rules of different defects were analyzed according to the characterization of surface quality,shrinkage state and stress distribution.The results show that the vacuum bubbles in the apparent defects do not exist when the mold temperature is above 120℃,the holding time is 20 s,and the cooling time is 60 s,while the surface air streaks are completely eliminated when the injection speed is less than 5 mm/s.With the increase of holding pressure,holding time and mold temperature,the geometric shrinkage of the products decrease significantly,and the dimensional accuracy and geometric deformation are effectively controlled.The residual stress of the product is also affected by the forming process,but the effect of annealing is more obvious,which is also an effective mean to reduce the residual stress.