The Runner Adviser Analysis is used to calculate the best runner, gate, and sprue dimensions to achieve minimal pressure drop and ensure that the part fills.
This analysis calculates the influence of the part geometry, material, and processing conditions, and the number of gates to determine the best runner system dimensions.
The Runner Adviser Analysis also suggests adjustments to the cross-sectional dimensions of the runner system, such as width, height, taper angle, and diameter; however, the runner type and shape, and the length of the runner section are not modified.
Note:
- Any parameters you set for the runner system may have recommended changes when the Runner Adviser analysis is performed. For example, the adviser may recommend a section size that is greater or smaller than the size you originally stipulated in the Gate Properties pane. Check the Summary for a list of potential changes.
- The aspect ratio of the cross-section may change, for example, the ratio of width to thickness in a trapezoidal runner.
With a set of fixed processing conditions and fixed volume, a runner system design is said to be optimum if it minimizes the energy consumption of the injection molding process among all feasible designs. In practice, minimizing the energy consumption of the injection molding process means minimizing the injection pressure at the end of the filling stage.
Within an upper limit of the injection pressure at the end of filling, associated with other fixed processing conditions, a runner system is said to be the best design if it has the minimum volume among all the feasible designs.
The Runner Adviser analysis is based on the following three assumptions:
- Flow viscosity in the runners follows the power-law model. The power-law index is a parameter of the Cross WLF material viscosity model. Because the viscosity influence is mainly due to the shear rate in the filling stage, this assumption makes it possible to use the power-law index to evaluate the pressure drop over each runner path quickly.
- The pressures at the gates of all of the cavities fed by the optimized runner system are the same as if each individual cavity was filled separately from its gate. This assumption implies that a simplification can be made by separating the cavities and performing the filling analysis on each of them.
- The flow rate in each runner segment is proportional to its downstream volume. This assumption is directly used for balancing runner systems in the pressure drop formulation, and the cavity volumes are required to determine the distributions.
Note: When you have applied the optimization to your runner system, you can perform a Fill or Fill+Pack analysis to see the effects of the changes. Use the Results Adviser to examine the shear rate for the gate and check that the temperature results are acceptable.