Study and optimization of effective parameters in the occurrence of Blush defect in the plastic injection molding process by analysis of variance

Plastic injection is one of the most important processes in plastic parts production. During this process, many defects can take place that affect products quality. This research focuses on decreasing one of these defects, called Blush. For this purpose, eight parameters with the probability of affecting the occurrence of this defect have been considered to be investigated. To study the effect or lack of effect, the extent, and the manner of effect of these parameters on the Blush defect, a Fractional factorial design of experiment with eight factors and two levels was performed. Then after finite element analysis in MoldFlow software and validation of analysis with experimental tests, the area of defect that occurred in each case was calculated by geometric methods. After ANOVA of the data, it was found that the parameters of runner diameter, holding pressure, flow rate, and melt temperature respectively, have the most significant effects on this defect. Then, for the four factors mentioned, an experimental design of Composite Cube Design was performed and after performing finite element analysis and analysis of variance on the data, it was found that all four parameters have a significant impact. It was also found that by increasing melt temperature, and holding pressure and reducing the runner diameter and flow rate to the optimal level, the area of blush defect will be reduced by 82.2%.