The screw for ice water filter machine was injection molded with acrylonitrile-butadiene-styretic (ABS)/polycarbonate (PC) [ABS/PC] alloy resin and its crack phenomenon after mechanical stress was analyzed by commercial Moldflow software. The cracked morphology and tensile properties of ABS/PC have been Studied by scanning electron microscopy (SEM) and universal test machine (UTM). The injection pressure and the residual stress has been compared with two injection molding conditions as actual manufacturing and reduced injection flow rate. This analysis has found that residual stress is higher at actual manufacturing condition. SEM study reveals that in the micrographs taken on the surface of cracked sample ABS rubber domains tend to extremely align in the direction of mold flow. The combined data suggest that the majority of the crack comes from residual stress in final part originated from higher injection pressure during injection-molding process. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2702-2708, 2009