The vent hole is used to discharge the gas in the cavity, improve the filling ability of the liquid metal, remove the supercooled liquid metal and scum which are flushed into the cavity first, and it can also be used as a sign to observe the liquid metal filling the cavity. See the process drawing for the location of air outlet.
Prevent the casting from forming hot spot due to too large air outlet, and even producing shrinkage cavity. The root diameter of the air outlet shall not be greater than 0.5 times of the wall thickness of the casting at the setting. That is to say, the diameter of air outlet shall be less than 12mm (0.5 * 24mm).
To prevent the excessive increase of air pressure in the mold due to the too small air outlet, the total cross-section of the root of the air outlet shall be 4cm2 larger than the total cross-section of the internal gate.
Therefore, the root diameter of the vent hole is designed to be 12mm, and 4 vents are designed for one box. In order to facilitate the removal of the mould, the taper with small upper part and large lower part shall be adopted, and the inclination shall be a = 1 ° 10 ‘
The total sectional area of air outlet is 3.14 * (1.2 / 2) m2 * 4 = 4.5cm2