Optimization of Processing Parameters for Plastic Injection Moulding Process towards Moulded Part Shrinkage

Plastic injection moulding process is a popular method to manufacture plastic components. In order to produce good quality moulded parts, processing parameters are important criteria to consider by moulders. In this study, optimization by Taguchi method was used to optimise moulding processing parameters towards shrinkage of a Polypropylene (PP) moulded part. The experimental works were performed according to matrix design of L-9 (3(4)) orthogonal array (OA), followed by signal to noise (S/N) ratio and analysis of variance (ANOVA) study. The shrinkage was calculated by measuring the dimension diameter of moulded part using a coordinate measuring machine (CMM). Based on the signal to noise (S/N) ratio analysis, the optimised processing parameters for outer diameter shrinkage were mould temperature at 45 degrees C, melt temperature at 250 degrees C, injection time at 0.72 s and injection pressure at 22 MPa. Referring to ANOVA result, the mould temperature was most significant factor with 37.58% contribution towards the shrinkage. Finally, the obtained shrinkage was 1.55% for the confirmation test using the optimised processing parameters.