Figure 7 shows a long, narrow box and lid. If only one center drop is used, the flow will
hit the hinge restriction before the gated cavity has filled. Because the hinge restriction
represents a higher pressure drop, the melt will stop at the hinge until the extremes of
the cavity are filled. At this point the pressure will rise, but because the center hinge
area had already started to freeze, the material will flow across from both ends, creating
a weld line along the hinge with possible air entrapment