Work out runner and riser sizing instantly with clear inputs, formula shown and shareable results.
A riser must hold enough liquid metal to feed solidification shrinkage, conventionally 20-30 percent of the casting volume, and be shaped so it freezes last: a height to diameter ratio of about 1.5 gives that. The gating system is proportioned to an unpressurised 1:2:2 ratio of sprue choke to runner to ingates so the mould fills without turbulence.
Riser volume
Riser cm³ = casting volume x riser fraction
Riser diameter
D = (4V / (pi x 1.5))^(1/3) for H = 1.5 D
Gating ratio
Sprue : runner : ingates = 1 : 2 : 2 for an unpressurised system
Riser cm³ = casting volume x riser fraction. A riser must hold enough liquid metal to feed solidification shrinkage, conventionally 20-30 percent of the casting volume, and be shaped so it freezes last: a height to diameter ratio of about 1.5 gives that.
Enlarging the runner and ingates downstream of the choke slows the metal and keeps the system full but not jetting, which reduces air entrainment and dross in the casting.
This calculator takes 3 inputs: Casting volume, Riser volume as share of casting, Sprue choke area. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.