Injection location temperature during packing and cooling

The injection location temperature moves toward the mold temperature during the packing and cooling phases because there is negligible flow from the barrel during these phases.

The injection location temperature affects the flow of the melt into the part during packing, usually by decreasing the flow. To achieve realistic warpage values, it is important to take the injection location temperature into account during the packing and cooling phases.

Note: The injection location temperature cools when using thermoplastic materials and heats when using thermoset materials.

The cooling calculation at an injection location node starts when the flow rate at that node drops below a small injection cooling criterion. Once the part has filled, or a short-shot has occurred, the software checks to determine whether cooling can start at each injection location. The criterion is a very low flow rate value, sufficiently small that the subsequent influence of barrel temperature on the injection temperature is negligible. When the flow rate at the injection node falls below this criterion, for two consecutive time steps, the injection node starts to cool. Until that time, the node is considered to be at the melt temperature. Thus, different injection locations can start cooling at different times. Once a location has started cooling, it will continue cooling regardless of the flow rate.

Different cooling calculation methods are used depending on the type of model that you are analyzing. In all cases, the appropriate local mold temperature values, HTC values and temperature-dependent material properties are employed.

Injection into hot runners

For injection into hot runners, no injection cooling is applied. The injection location is maintained at the melt temperature.

Injection into cold runners

For injection into beam cold runner elements, cooling occurs by the standard beam temperature calculation in all flow solvers, with no thermal convection from the barrel.

Injection into the cavity with no runner system

For direct injection into the cavity, where no runner system is modeled, Midplane and Dual Domain analyses assume 2D cooling through both sides of the thickness, similar to the surrounding part. 3D analyses assume cooling through the walls of a cylindrical gate. The cylinder diameter for the cooling calculation in the 3D flow solver is set to the gate contact diameter, entered by the user as Automatic or Specified. To allow for injection into a thin part, the cylinder diameter is limited to twice the local part thickness at that injection location.