Application of the Taguchi method to optimize the surface quality of gas assist injection molded composites

Gas assist injection molding of short glass fiber reinforced composites has become an important process in industry, because it enables the production of parts with thick and thin sections and with a good structural rigidity. However there are some unsolved problems that confound the overall success of this technique. Part roughness of the composites caused by inappropriate mold design and processing conditions is one of them. An L' 18 experimental matrix design based on the Taguchi method was conducted to optimize the surface quality of gas assist injection molded composites. The material used was a 35% glass fiber reinforced Nylon-6 composite. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. A float-shape mold cavity was used. After molding, the surface quality of the parts was characterized by a roughness meter. For the factors selected in the main experiments, melt temperature and gas injection delay time were found to be the principal factors affecting the surface quality of gas assist injection molded composites. Experimental investigation of a gas assist injection molding problem can help reveal the formation mechanisms of surface roughness, so that steps can be taken to improve the surface quality of molded parts.