In components manufactured by injection molding, the regions interested by the presence of a weld surface show worse mechanical properties, especially in case of fiber reinforced thermoplastics because of unfavorable reinforcement orientation in proximity of the weld line. The position and the shape of a welding surface, which is formed where two or more different flow come to converge, can be modify generating unbalance conditions between flow fronts. This work analyzes the effect of different strategies aimed to induce a variation in weld line morphology and fiber orientation close to the weld surface through the promotion of a pressure gradient between flow fronts, which causes a polymer flow (in-flow) during the packing phase. The main goal is to increase the mechanical properties of weld lines, and consequently, the strength of the whole component.