This graph shows the relationship between the fill pressure and the time required for fill calculated for a bumper endcap. The minimum separates two regions of fill behavior. In the first region, the fill behavior can be predicted from isothermal analysis.
Viscosity controls the fill pressure.
In the second regime, heat transfer controls fill pressure. A significant amount of cooling takes place during fill in this region. Because of this, the flow cross section is being constricted during fill. The resin viscosity also goes up during fill. These two changes act to increase the required fill pressure.