Abstract: Pipes with curved sections were injection-molded by the water-assisted co-injection molding process (WACIM) on a lab-developed WACIM system, and their wall thickness was analyzed. The results indicated that, at the outer convex side, the total wall thickness and wall thickness of inner layer were much bigger for the curved pipes molded by the overflow WACIM (O-WACIM), but at the inner convex side, both of them were smaller for the curved pipes molded by the shortshot WACIM (S-WACIM). However, the average total wall thickness and the average wall thickness of inner layer for the curved pipes molded by S-WACIM were smaller than those by O-WACIM, and they became much smaller in the curved section of the pipes. At the outer convex side of the pipes, the total wall thickness and the wall thickness of inner layer increased with an increase of bending angle, but at the inner convex side, they tended to decrease.

Key words: water-assisted co-injection molding, curved pipe, residuall thickness