Abstract:

An experimental study was carried out to investigate the effect of the projectile on the wall thickness of pipe fitting in the water-projectile-assisted injection molding（W-PAIM）. Through constructing an experimental platform， the effect of the four factors including the projectile material， head shape， straight length and cross-sectional size on the residual wall thickness of the W-PAIM polypropylene （PP） pipe fittings were studied. A comparative experiment showed that the residual wall thickness of the pipe fitting formed by the PA6 projectile was more uniform than those of the PA6， ABS and PTFE projectiles， indicating the optimum quality. Among the heads with the hemispherical， parabolic， arc and conical shapes， the parabolic head achieved the optimum quality fittings. For the projectile with a length of 7 mm in straight section and a section size of 13 mm， the obtained residual wall thickness was the most uniform and the quality of the molded pipe fitting was the best.

Key words: water-projectile-assisted injection molding, projectile, residual wall thickness, pipe