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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.
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.