Abstract: The problem of weld line on large injection molded products caused by multiple gates was explored using hot runner and automatic control technologies. The injection mechanism in hot runner/valve-gate and the silting pattern were analyzed, aiming to improve the operation and design of valve-gate system. Through a simulation of the valve-gate process of a car front bumper, a general design process of the valve-gate system using Moldflow was obtained.

Key words: weld lines, valve-gate, injection molded product, Moldflow