Abstract: The effects of eight processing parameters on the residual wall thickness of water-assisted injection molded parts were investigated. The processing parameters were melt temperature, mold temperature, short-shot size, water injection delay time, water pressure, water temperature, melt filling speed, and pressure. The experiments were carried out on a lab-developed water injection system and a mold with curved circular pipe cavity. The material used for the experiments was polypropylene. It was found that some processing parameters had effects on the wall thickness invariance of the curved sections. When the water injection time increased and the water pressure and melt temperature decreased, the wall thickness invariance of the short-shot filling section reduced. The wall thickness invariance became larger with increasing melt temperature.

Key words: water-assisted injection molding, processing parameter, curved tube, wall thickness