Keywords:Factor, Response surface, Shrinkage, High-Density Polyethylene
Nowadays, the plastics industry plays an essential role in the country's internal and external industries. Especially assembled products, product quality is an essential aspect of production. There are various product problems. Shrinkage is an inevitable problem with plastic products. This research is to determine the factors that affect the shrinkage of the screw cap of the plastic bottle made of High-Density Polyethylene (HDPE) material, where the shrinkage of the workpiece affects the assembly between the screw cap of the water bottle and the water bottle. Therefore, Response Surface Methodology (RSM) experimental design principles was used to determine the factor affecting the shrinkage of the workpiece, namely the melt temperature of plastic (Tm), mold temperature (Tw), and cooling temperature (Tc). The 9 (8+1) experiments were performed with 2 replications at a confidence level of (α) 95 %. A total of 18 experiments found that the significant relevant factor affecting the shrinkage of the bottle cap specimens was the melting temperature of plastic (Tm) of 190 oC, the mold temperature (Tw) of 60 oC and cooling temperature (Tc) is 45 oC, with a minimum shrinkage of 1.39% and can be found that defects decreasing were 12.08%. Therefore, it can be concluded that applying the Responsive Surface Method (RSM) experimental design principles to help determine the appropriate factor that transmits the minimal shrinkage effect affects the quality and reduce production costs of the bottle cap.
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