KEVOS® MAKEOS · Fabrication
Casting Gating System Choke Area
What choke (sprue) area fills this mould in the planned pouring time?
Velocity of metal at the base of the sprue from the effective head, the choke area needed to pour a casting in a set time, the equivalent round sprue diameter and gate areas for a chosen gating ratio.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Poured mass (casting plus runners) | kg | Mass of metal poured, including runners and risers. |
| Liquid metal density | kg/m³ | Density of the liquid metal (grey iron about 7000, steel about 7000, aluminium about 2400 kg/m³). |
| Effective metallostatic head | mm | Effective head at the choke (for top gating, the sprue height; reduce it for bottom gating as the mould fills). |
| Pouring time | s | Target pouring time from foundry practice for the casting weight and section (often found from an empirical rule). |
| Flow efficiency (discharge coefficient) | Flow efficiency of the gating system (about 0.7–0.9). | |
| Gating ratio: runner area ÷ choke | Runner area relative to the choke (e.g. 1 : 2 : 2 unpressurised gives 2). | |
| Gating ratio: total gate area ÷ choke | Total gate area relative to the choke. |
Method and formulas
- Velocity v = √(2 g h).
- Choke area A = W ÷ (ρ t C_d v).
- Runner and gate areas = choke area × gating ratios; round sprue diameter = √(4A/π).
- Example: 40 kg poured in 12 s from 200 mm head needs a choke of 300.54 mm² (19.562 mm diameter).
Limitations
- Simple Bernoulli model; friction, bends and turbulence are lumped into the flow efficiency.
- Pouring time rules and gating ratios depend on the alloy and casting; use foundry practice.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size sprues and gates for a new pattern
- Check pouring time for thin-walled castings
- Compare pressurised and unpressurised gating
Who it is for
- Foundry engineers
- Pattern makers
What you get
- Metal velocity at the choke
- Choke area and equivalent sprue diameter
- Runner and total gate areas
Interpreting the result
- Unpressurised systems (gates larger than the choke) give calmer filling for aluminium; pressurised systems suit iron.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1404–1420. Topic reference; no source tables or recommended settings are reproduced.
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