7.4.2.1.4 The combined effects

Consequently, a very small area ratio results in a very large resistance, and when therefore the resistance resulting in a zero gate velocity (like a closed valve). Conversely, for a large area ratio, the resistance is insensitive to variations of the gate area and the velocity is reduced with increase the gate area. Therefore a maximum gate velocity must exist, and can be found by

(7.26)

which can be solved numerically. The solution of equation () requires full information on the die casting machine.

A general complicated runner design configuration can be converted into a straight conduit with trapezoidal cross-section, provided that it was proportionally designed to create equal gate velocity for different gate locations¹⁸. The trapezoidal shape is commonly used because of the simplicity, thermal, and for cost reasons. leave it for now, better presentation needed

Figure: Design and dimensions of the runner for the example . The length, , represents different runner design qualities. The gate design is made of straight lines to the gate area, creating a symmetrical gate.

= 100 true mm

Figure: Gate velocities as a function of the area ratio for constant pressure.

= 100 true mm

Figure: Gate velocities as a function of the area ratio for constant power.