Setting pouring time and gating areas
Pour too slowly and you get cold shuts and misruns; pour too fast and you erode the mold and drag in inclusions. This calculator uses the classic iron-casting relation t = K × (1.1 + wall ÷ 20) × √weight, with wall in mm and weight in kg, and converts your pound and inch inputs automatically. A 220 lb casting with a 0.4 in wall works out near 16 seconds, which lines up with common foundry practice.
Once the time is set, the flow rate is set, and the flow rate fixes the minimum (choke) area. That part is straight Bernoulli: choke area = weight ÷ (density × discharge coefficient × velocity × pouring time), with velocity taken as √(2gH) from the effective head. The discharge coefficient lumps together friction and bend losses and normally falls between 0.6 and 0.9.
The gating ratio is the area relationship between sprue, runner and ingates. A pressurized system that narrows downstream (for example 4:3:2) keeps the system full and steady but runs fast enough to risk erosion, while an unpressurized system that widens (1:2:2 or 1:4:4) slows the metal down and reduces oxide and inclusion problems in aluminum and ductile iron. Confirm a final gating design with solidification simulation and an experienced foundry engineer.
Frequently asked questions
Use casting weight for the basic calculation. If risers and runners are unusually heavy, check total poured weight separately when you size ladle capacity and pouring rate.
The result is the total ingate area. Divide it by the number of ingates, and spread them toward thinner sections to balance fill and temperature distribution.