注射成型工艺对制品收缩与翘曲的不同影响

以PP盒形制品为例，设计了一种测量方案使得收缩与翘曲可以独立度量，分别考察了这两者在不同工艺水平下的变化。使用单因素方差分析表确定熔体温度、保压压力等注射成型工艺参数对收缩与翘曲的影响程度，并以置信区间图示出各参数对收缩与翘曲的影响规律。通过对实验数据的总结发现，保压压力对收缩影响最为显著，而模具温度对翘曲影响最显著。制品收缩与翘曲随工艺参数变化呈3种不同特征：收缩与翘曲呈相反的变化趋势，提高注射速率或熔体温度，制品收缩率减小而翘曲增大；随保压压力升高收缩率单调减少而翘曲呈“U”形曲线变化；调整其他工艺参数，收缩与翘曲有相同的变化趋势。这些影响规律的总结为减小注射成型中塑料制品的收缩与翘曲提供依据。

Different effects of processing conditions on shrinkage and warpage of injection molded parts

Shrinkage and warpage (S/W)affected by processing conditions were measured separately by an innovative measuring method based on a polypropylene box-shaped part.The single factor analysis of variance（ANOVA） was used to determine whether processing conditions, such as melt temperature and holding pressure had significant effects on S/W or not.Different laws of S/W affected by processing conditions were set out on confidence interval graphs.These results indicated that holding pressure was the most significant factor for shrinkage, but mold temperature for warpage.With changing processing conditions, S/W variations were summarized as follows:contrary effects, shrinkage decreased but warpage increased with increasing melt temperature and injection velocity. Shrinkage reduced monotonously and warpage varied as U shape curve with increasing holding pressure. Shrinkage and warpage varied in the same way with changing other conditions.These results could be used to help minimize shrinkage and warpage of injection molded parts.