Experimental matrix design to optimize the weldline strength in injection molded parts

The forming of weldlines wherever polymer flow fronts meet is one of the problems that confound the overall success of injection molding technology. In this study, an L'18 experimental matrix design based on the Taguchi method was conducted to optimize the weldline strength of injection molded thermoplastics. Experiments were carried out on a 4.1 oz injection molding machine. A plate cavity with an obstacle at the center was used to create a weldline. After molding, the weldline strength of the parts was measured with a tensile tester. Of the factors selected in the main experiments, melt temperature and mold temperature were found to be the principal factors affecting the weldline property of injection molded thermoplastics. Weldline strengths of injection molded parts increase with the size of the obstacles.