As a rule of the way resin flows inside a plastic resin mold, it has the property that “molten resin flows into places where it can easily flow.”
For example, when resin flows from a thick runner into the cavity at the restriction gate, it stops for a moment at the gate and then flows into the cavity. If this was a multi-cavity mold, the resin would basically be filled from the cavity far from the sprue and then into the cavity near the sprue. This phenomenon is called vegetation, and molding defects that cause unfilled defects in the molded product close to the sprue are called vegetation marks. It is said that vegetation marks are likely to occur in molds that have many runners placed in parallel.