Overpacking occurs in complex parts that have more than one injection location when flow fronts meet before the part has filled.
In the following animation, the material from the central gate merges with the flow from the other two gates before the part has filled, causing underflow and overpacking. To overcome this type of overpacking, divide the part into imaginary sections in which the flow fronts meet at the end of fill. Design the runners to ensure that the pressure in each section is equal.
In the following animation, the gates have been moved so that each section of the mold fills simultaneously.
Runners can be designed to achieve balanced flow and prevent underflow by equalizing the pressure where the flow fronts meet. You can use the pressure results to observe the pressure in the cavity.