Abstract:Water-projectile-assisted injection molding (W-PAIM) process is a new processing technology in which the pressurized water is utilized to drive a projectile to penetrate in the core melt to manufacture hollow plastic pipes. The effects of the processing method and processing parameters on the residual wall thickness (RWT) of W-PAIM pipe were investigated based on a lab-developed experimental platform. The experiments results of short-shot W-PAIM (W-PAIM-S), overflow W-PAIM (W-PAIM-O), short-shot WAIM (WAIM-S), overflow W-PAIM (WAIM-O), WAIM and W-PAIM pipes were compared and it is found that the RWT of W-PAIM pipe is much thinner and the RWT of W-PAIM-O pipe is thinner and more even than that of W-PAIM-S pipe. Orthogonal experiments were carried out to study the influences of the main six processing parameters, including the melt temperature, water pressure, melt pressure, packing time, water injection delay time and mold temperature, on the RWT of W-PAIM-O pipe. It is found that the main influencing parameters are the water injection delay time and the melt temperature. The total percentage of influences of these two factors is up to above 70%. The melt pressure, water pressure and packing time have a total percentage of influences of factors less than 17%, which means that they have little effects on the RWT of W-PAIM-O pipe. The RWT of W-PAIM-O pipe increases with increase of the water injection delay time. With increase of the melt temperature, the RWT of W-PAIM-O pipe first decreases and then increases.