Optimisation of injection process parameters to minimise mould deflection: design of experiment

This research aimed to estimate the mould deflection by installing the strain gauges on the modified injection mould, which was analysed by the analysis of variance (ANOVA) method. Also, studied the correlation of the maximum mould deflection, thickness and defect of the moulded part. The optimisation of the injection parameters to minimise the mould deflection and defect was examined. There are seven processing factors with three levels of melting temperature, mould temperature, injection pressure, holding pressure, injection speed, holding time and cooling time, which are designed by using Taguchi's experimental design. The parameter factors are statistically significant with P-values less than 0.05. The levels of those processing parameters are compared by Tukey pairwise comparisons using the Tukey method and 95% confidence. The optimum processing conditions attaining the lowest value of the maximum mould deflection of polypropylene (PP) and Acrylonitrile butadiene styrene (ABS) parts were investigated. The results showed that the mould deflection shows a good relation to those of thickness and flash defect; however, the occurrence of the short shot part presented a weak relation.